This article was downloaded by: [UOV University of Oviedo]On: 13 November 2014, At: 10:33Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK

New Zealand Journal of Geology and GeophysicsPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/tnzg20

Paleoseismicity and mass movements interpretedfrom seismic‐reflection data, Lake Tekapo, SouthCanterbury, New ZealandPhaedra Upton a & Erich C. Osterberg b ca Department of Geology , University of Otago , PO Box 56, Dunedin, 9054, New ZealandE-mail:b Department of Geology , University of Otago , PO Box 56, Dunedin, 9054, New Zealandc Department of Earth Sciences , Dartmouth College , 6105 Fairchild Hall, Hanover, NH,03755, USAPublished online: 19 Feb 2010.

To cite this article: Phaedra Upton & Erich C. Osterberg (2007) Paleoseismicity and mass movements interpreted fromseismic‐reflection data, Lake Tekapo, South Canterbury, New Zealand, New Zealand Journal of Geology and Geophysics,50:4, 343-356, DOI: 10.1080/00288300709509841

To link to this article: http://dx.doi.org/10.1080/00288300709509841

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose ofthe Content. Any opinions and views expressed in this publication are the opinions and views of the authors,and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be reliedupon and should be independently verified with primary sources of information. Taylor and Francis shallnot be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and otherliabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to orarising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

New Zealand Journal of Geology & Geophysics, 2007, Vol. 50: 343-3560028-8306/07/5004-0343 © The Royal Society of New Zealand 2007

343

Paleoseismicity and mass movements interpreted from seismic-reflection data,Lake Tekapo, South Canterbury, New Zealand

PHAEDRA UPTON

ERICH C. OSTERBERG*Department of GeologyUniversity of OtagoPO Box 56Dunedin 9054, New Zealandphaedra.upton@stonebow.otago.ac.nz

*Present address: Department of Earth Sciences, DartmouthCollege, 6105 Fairchild Hall, Hanover, NH 03755, USA.

Abstract A 61 km seismic survey of Lake Tekapo wasshot in 2001 to identify tectonic features observed onshore.The survey revealed bedrock highs, lake-floor offsets, and aseries of mass movement deposits, all interpreted to resultfrom tectonic uplift and paleoearthquake events. Fine-grainedsediment within the lake basin, imaged as uniform, regular-spaced, laminated reflectors, is at least 145 m thick at thesoutheastern end of the lake. Bedrock highs (>70 m of relief)are found along-strike of the Irishman Creek Fault and ForestCreek Faults, and are interpreted as long-term features thatare repeatedly raised in earthquakes and lowered by glaciers.Movement on them since the last glacial maximum has offsetthe lake floor by 10-20 m, consistent with estimated upliftrates on these faults from previous studies. The seismic re-flection data suggest that both faults extend into the centre ofthe lake, terminating against a north-south-oriented structure,possibly the Tekapo River Fault. Mass movement depositsare observed within the sediment pile, and we attribute themto paleoearthquakes on local faults or the more distant plateboundary. Using a sedimentation rate of 8 mm/yr, we datetwo sets of mass movement deposits at 1720 ± 344 yr BPand 2810 ± 562 yr BP.

Keywords Lake Tekapo; seismic reflection; MackenzieBasin; faults; tectonics; deformation

INTRODUCTION

The fluvio-glacial lakes of the central South Island of NewZealand (Fig. 1) contain a potentially valuable record ofglacial history, climate change, and tectonic activity over thelast c. 16-20 000 yr since the alpine glaciers of the last glacialmaximum (LGM) retreated upstream of the lake basins. Inthis study we present 61 linear kilometres of single-channelseismic reflection data from Lake Tekapo and concentrate onthe tectonics of the region and evidence found in the seismicreflection record of pre-historic earthquakes.

G07016; Online publication date 10 October 2007Received 9 July 2007; accepted 17 September 2007

Comparison of the Nuvel-1A relative plate motion vectorbetween the Australian and Pacific plates in the central SouthIsland (De Mets et al. 1994) with late Pleistocene displace-ment rates along the Alpine Fault suggests that c. 25% of thisrelative motion occurs away from the Alpine Fault (Norris& Cooper 2001). Qualitatively, the presence of the SouthernAlps (Fig. 1) also suggests that a proportion of the relativemotion is accommodated east of the fault. Recently, therehas been a series of studies that focus attention on the lociand nature of deformation within the outboard region (Cox&Findlay 1995; Smith et al. 1996;Templetonetal. 1998a,b;Long et al. 2003; Upton et al. 2003, 2004). A seismic surveyof Lake Tekapo provides an opportunity to continue to mapthese structures and to elucidate the relationship between theIrishman Creek Fault and the Forest Creek Faults. Long etal. (2003) inferred the possible existence of a north-south-oriented structure, the Tekapo River Fault, from seismic data,velocity models, and the exposed geology. Our seismic surveyof Lake Tekapo provides further evidence for the existence ofthe structure, although it does not appear to have been activein the past 16-20 000 yr.

TECTONIC SETTING AND REGIONAL GEOLOGY

Oblique continental collision along the Australian/Pacificplate boundary in the South Island of New Zealand has re-sulted in c. 800 km of dextral strike-slip movement and asmuch as 90 km of convergence in the past 2-5 m.y. (Norriset al. 1990; De Mets et al. 1994; Sutherland 1999) (Fig. 1). Inthe central South Island, late Pleistocene displacement ratessuggest that c. 75% of relative plate motion is taken up on theAlpine Fault, a dextral reverse fault that extends for 600 kmalong the western edge of the Southern Alps (Norris & Cooper2001). The remainder of the relative plate motion is accom-modated east of the Alpine Fault, resulting in a 70-200 kmwide zone of mountain building (Walcott 1978; Norris et al.1990; Cox & Findlay 1995; Becker & Craw 2000). Southeastof the Main Divide, a broad oblique fold and thrust belt hasformed. A number of intermontaine basins of varying sizesexist within the region between the Main Divide and therange front. The largest of these is the Mackenzie Basin, thegeographic focus of this study (Fig. 1).

A basement of metagreywacke (Torlesse greywacke),which was metamorphosed and then uplifted c. 10 km in theMesozoic, underlies the Southern Alps in central Canterbury(Gair 1978; Field & Browne 1986). The eastern ranges consistof low-grade metamorphic rocks, with higher grade equiva-lents currently being uplifted from the middle crust to thewest of the Main Divide. Where exposed on the edges of theMackenzie Basin, these rocks are unfoliated metagreywackesof prehnite-pumpellyite faciès, with minor zones of weaklyfoliated pumpellyite-actinolite faciès (Gair 1967). Juxtaposi-tion of rocks of different metamorphic grades occurred before

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

344 New Zealand Journal of geology and geophysics, 2007, Vol. 50

Lake Tekapo

Lake PukakiBen Ohau

Range

Study Area, Figure 2

Mackenzie Basin

Fig. 1 digital elevation model(from geographX) of the Southisland of New Zealand showingthe alpine Fault, the MarlboroughFault System (Wairau Fault; aF,awatere Fault; cF, clarence Fault;hF, hope Fault; PPFZ, Porters PassFault Zone), and active faults in theregion of interest. MdFZ, Maindivide Fault Zone; OF, Ostler-great grove Fault; icF, irishmancreek Fault; FPF, Fox Peak Faults;FcF, Forest creek Faults. The boxencloses the study area shown inmore detail in Fig. 2. Inset: The platetectonic setting of New Zealand.Relative plate motion vectors arefrom de Mets et al. (1994).

the cenozoic uplift of the Two Thumb Range (Fig. 2), prob-ably during Mesozoic post-metamorphic uplift (James 1998;Upton et al. 2004).

Topographically, the outboard region consists of north-and northeast-trending mountain ranges, northeast-trendingintermontaine basins, and north-trending valleys and glaciallycarved lake basins (Fig. 1). Major geological structures in theregion trend similarly. The Ostler/great groove Fault andthe Fox Peak Faults trend NNe-N, uplifting the ben Ohauand Two Thumb Ranges, respectively (gair 1967; Smith etal. 1996; James 1998; Upton et al. 2004) (Fig. 1). The Maindivide Fault Zone, the irishman creek Fault (icF) and theForest creek Faults (FcF) trend northeast, approximatelyparallel to the alpine Fault (cox & Findlay 1995; chetwin1998; Upton et al. 2004) (Fig. 1).

Mackenzie Basin and Irishman Creek FaultThe Mackenzie basin is conspicuous as a relatively largelowland region within the otherwise mountainous Southernalps (Fig. 1). it covers c. 2000 km2 and has an average el-evation of c. 700 m. a significant structural feature cutting

through the Mackenzie basin is the icF (Fig. 1,2). This is areverse fault, striking parallel to the alpine Fault and dippingc. 55°Se (Fox 1987; chetwin 1998; Kleffmann 1999). TheicF is probably the major structure within a broader zoneof deformation, the irishman creek Fault Zone (Fox 1987;cox & barrell 2007). The fault zone is c. 15 km wide, gener-ally trends eNe, and is defined by a series of eNe-trendingfault traces within glacial outwash deposits to the southeastof Lake Tekapo. Upton et al. (2004) suggested that it can besensibly projected across Lake Tekapo into the FcF, whichstrike northeast and extend at least as far as the RangitataRiver (Fig. 1). anortheast extension of the icF has also beenproposed on the basis of a series of uplifted basement blocks,including Mt John, Mt hay, Wee Mcgregor, and possiblyMotuariki island, which run approximately along-strike ofthe icF (Fox 1987).

Movement on the icF has uplifted the Old Man Range,forming a scarp with a relief of 150 m. The Old Man Range isoverlain by moraine and outwash sediments that predate theLgM (28-19 ka; Suggate & almond 2005). it is probable thatthis area has not been covered by ice since at least 160 ka (cox

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

Upton & Osterberg—Seismic reflection, L. Tekapo 345

Fig. 2 The study area showingLake Tekapo and bathymetry(fromirwin 1978),the Two ThumbRange, hall Range, active faults(Upton et al. 2004; cox & barrell2007), and other localities referredto in the text. Major rivers feedingthe lake are the godley River,which comes in from the north,and the cass River which comesin from the west. The positions ofthe seismic lines are shown. Linesare numbered 1-8.

5720000°N6

McCauley

Active fault

Active fault inferred

Fault trace

~i Mt Joseph region of micro-seismicity (Fox 1987)

& barrell 2007). Pliocene glentanner beds exposed within theOld Man Range dip moderately to the southeast. basement isnot exposed in this region; it is inferred on the basis of seismicreflection data that cenozoic marine strata may underlie thelate cenozoic strata (chetwin 1998). combined gravity andseismic modelling suggest that on the downthrown side of thefault, the top of the cenozoic sequence is found at c. 800 mand the basement is found at c. 1800 m below ground surface(chetwin 1998; Kleffmann 1999). a n offset in the order of1500 m across the icF is inferred (chetwin 1998; Long et al.2003). a recurrence interval for major events on the icF in thelast 5000 yr of 1290 ± 90 yr has been determined from datingof weathering rinds on boulders on scree slopes along the faulttrace (McSaveney 1991). a vertical slip rate of c. 0.6 mm/yris estimated from offset of Pliocene gravels across the fault(chetwin 1998).

Seismicity within the Mackenzie Basinhistorically, seismicity in the Mackenzie basin is low relativeto other parts of New Zealand (haines et al. 1979). The instal-lation of a microearthquake network to monitor the raising ofthe water level of Lake Tekapo recorded a large number ofmicro-earthquakes from 1975 to 1983 (Reyners 1988). Themicroseismicity in the basin correlates well with the surfacetraces of the icF, Ostler/great groove, and Fox Peak Faults(Fox 1987; Reyners 1988). Focal mechanism solutions fortwo 2-4 ML events near Lake Tekapo show them to be obliquesinistral strike-slip events (Leitner et al. 2001). Lin this region,focal mechanisms show a dominant thrust component whichtends to be aligned with the NNe strike of the mapped faults(Leitner et al. 2001 ). a linear concentration of events along thebase of Mt Joseph does not correlate to a known fault (Fig. 2)(Fox 1987; Leitner et al. 2001, fig. 17). These events along the

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

346 New Zealand Journal of geology and geophysics, 2007, Vol. 50

northern margin of the Mackenzie basin, in conjunction withits alignment parallel to that of the icF, suggests that an activefault zone may exist along this range front (Fox 1987).

LAKE TEKApO

Lake Tekapo is the easternmost of three glacially carved lakesin the Mackenzie basin and is the focus of this study (Fig. 1,2). it is 27 km long with a maximum width of 6 km. The lakeis steep sided to a depth of c. 90 m, below which the lakebed becomes relatively flat. The deepest area is the 120 mdeep Motuariki basin, located southeast of Motuariki island(Fig. 2). The other lakes in the Mackenzie basin are LakePukaki and Lake Ohau, situated 30 km and 60 km southwestof Lake Tekapo, respectively (Fig. 1). These are similar toLake Tekapo in origin, geological setting, and morphology(irwin 1970a,b, 1973).

Pickrill & irwin (1983) conducted an initial seismic re-flection survey (3.5 khz) of Lake Tekapo, and collected grabsamples and gravity cores. Seismic penetration in their surveywas in the order of 25 m. They described the sediment withinLake Tekapo as dominantly fluvio-glacial gravel, sand, silt,and clay sourced from the godley glacier via the godleyRiver and fluvial sediment from the cass River (irwin 1978;Pickrill & irwin 1983). The godley delta controls the morphol-ogy of the northern third of the lake (to c. line 7 of this study).Topset beds of sand and gravel give way to finer graineddeposits to the south with increasing distance from the delta.excluding the cass delta, sediment south of the godley deltais dominated by mud and clay (Pickrill & irwin 1983).

gravity cores collected by Pickrill & irwin (1983) showthat the lake basin and lower foreset sediments are varved. inthe Motuariki basin there are 10-12 major varves per 10 cmof core, yielding a sedimentation rate of 1 ±0.1 cm/yr sup-ported by 210Pb data (Pickrill & irwin 1983). a recent studycalibrated 19th century seismic events to turbidites withintwo cores (i-1397,1.9 m; i-1398,2.2 m; collected by the Na-tional institute of Water and atmospheric Research in 1991)taken from the middle of the Lake Tekapo basin (Fig. 2),and determined a sedimentation rate of c. 0.8 cm/yr over thepast 350 yr, which were then correlated to the environmentalmagnetic signal (Quinn & Wilson 2004). We use this valuefor the sedimentation rate as an average for the central lakebasin; however, without coring in the regions of interest, itis at best only an initial approximation. Sedimentation ratesincrease to >2 cm/yr on the upper foreset slope of the godleydelta (Pickrill & irwin 1983).

Lake shore geologyFieldwork was carried out along the southern shore of LakeTekapo, taking advantage of extremely low lake levels in thewinter of 2001 that exposed rocks usually under water.

Bedrock outcrops

a n almost continuous outcrop of Torlesse greywacke is foundalong the southwestern shore of Lake Tekapo, from grid ref.i37/073878*to 088917. The basement rocks along the south-western shore of Lake Tekapo are all uncleaved greywacke of

*Grid references refer to the New Zealand map series NZMS 260,based on the New Zealand Map grid projection. References indicatemap sheet (e.g., I37) followed by location in metres easting (first threedigits) and northing (last three digits). Location is precise to 100 m.

textural zone 1 (TZ1) (Long et al. 2003). bedding formlinesstrike c. 030º with moderate to steep dips (60-90°). a s previ-ously described by Fox ( 1987), two groups of linear fractureswithin the bedrock were observed along the eastern base ofMt John. One group of fractures trends parallel to the strike ofMt John and its bedding formlines (c. 030°), and the secondgroup crosses the mountain obliquely (c. 070°). Slickensideson closely spaced bedding planes dipping steeply to thesoutheast indicate reverse motion (Fox 1987).

A zone of cataclasite and fault gouge with some calcitecementation is found at the northern end of the bedrockexposure (grid ref. i37/090920) (Fig. 3a). The fault rocksextended 40 m across the strike. it is likely that the fault rocksare more extensive beneath the beach. The orientation of theshears within this fault zone range from 075° to 108°, withdips to the south ranging from 40° to 80°.

along the southeast shore of the lake, the basement rocksare also TZ1 uncleaved greywacke, oriented at c. 062/16°S. awell-cemented fault breccia was found parallel to the bedding(grid ref. i37/088916, Fig. 3b). The breccia layers are up to1 m thick and contain angular blocks of TZ1 greywacke upto 5 cm in diameter. The lateral extent of the breccia rangesup to 20 m. The fault breccia layers have been folded (foldaxis 154/16°SW, plunging to the south).

SedimentFine-grained sediment is exposed in three cliffs along thewestern edge of the lake (grid ref. i37/094925, 080958,086978). This sediment is located above current lake levelsand was presumably deposited soon after the last deglaciationwhen lake levels were considerably higher than they are today(cox & barrell 2007). The northern two exposures are flatlying, but a low-amplitude fold is observed in the sedimentnext to the projected eastern extension of the icF (grid ref.i37/093322, Fig. 3c). The folded sediment forms a synclinalstructure with limb angles of c. 8°. Small-scale faults and foldsare also observed in the sediment with offsets generally in theorder of 5 cm. The faults have reverse motion and are oriented042/45°SW and 090/22°N (Fig. 3d). although we believethat these features are related to deformation along the icF,we cannot discount the possibility that these low-amplitudefolds and small offset faults may have developed as a resultof drainage of the lake basin during deglaciation.

SEISMIC SURVEY OF LAKE TEKApO

We conducted a seismic reflection survey in Lake Tekapoconsisting of eight lines, three along the length of the lake andfive at right angles to the long axis of the lake, covering a totalof 61 km (Fig. 2). The seismic reflection data were collectedon 10-11 February 2001 using a Ferranti-ORe geopulseSub-bottom Profiling System™. a power level of 350 J wasused with a 0.5-2.0 pulse/s firing rate. Vessel survey speedranged from c. 3 to 5 knots, resulting in a c. 1.5-3.0 m seis-mic shot spacing interval. a handheld garmin gPS recordedthe vessel position at a regular interval during the survey. aFerranti-ORe 5210a Receiver™ was used to process the rawseismic data with flat gain, time-varied gain, and a bandpassfilter (500-2000 hz). Seismic profiles were all printed on ane P c 4800™ graphic recorder, for which a constant seismicvelocity of 1600 m/s was assigned for all time-depth conver-sions. The boomer and hydrophone array were towed behinda 7 m long Stabicraft vessel powered by an outboard engine.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

Upton & Osterberg—Seismic reflection, L. Tekapo

A

347

Fig. 3 A, Fault gouge exposed on the western shore of Lake Tekapo(grid ref. i37/090920). The gouge is made up of dark grey and dark redmaterial, finely ground with bits of crushed rock. B, Well-cementedbreccia exposed on the eastern shore of Lake Tekapo (grid ref.i37/088916). The breccia layer has been gently folded (dashed linesshow folded bed) and plunges to the south. C, Folded lake sedimentson the southwestern shore of Lake Tekapo, view looking to the west,(grid ref. i37/093322). D, Small fault within lake sediments: hammer(length 35 cm) lies along the fault which has c. 5 cm of offset. Thefault dips to the northwest, has reverse motion up to the north, and isconjugate to the icF.

The low noise levels of the outboard engine combined withcalm conditions during the 2-day survey resulted in high-quality seismic data.

Description and interpretation of seismic featuresOur objective is to use the seismic reflection data to mapwithin the lake those tectonic features that have been previ-ously described in the region, and to estimate the timing ofmass movement deposits that may indicate seismic activity.

Three seismic units have been identified from the seismicreflection data from Lake Tekapo. They define a stratigraphicsequence from oldest to youngest: ( 1 ) basement, (2) moraine,(3) fan and lake fill sequences. Other features observed withinthe lake basin include natural gas and mass movement de-posits.

Unit 1—basement

acoustic basement is seen on most lines (e.g., line 2, Fig. 4).bedrock is characterised in the seismic profiles by a smooth,high-amplitude reflector below which there are few, if any,

coherent reflectors. basement in this region is greywacke(Torlesse) and is observed dipping steeply (5-40°) beneathonlapping, fine-grained sediment near the lake shore and alsoas basement highs in the northeast and southwest regions ofthe lake. its smooth surface and steep incline is indicative ofglacial scouring, probably over several Pliocene-Pleistoceneadvances and retreats. Nowhere is the bottom of either lakebasin visible in the seismic data, although bedrock is visiblebeneath fine-grained sediment to depths of >250 m belowlake level (145 m below the lake floor).

Unit 2—moraine

Moraine is distinguished from bedrock by its lumpy appear-ance caused by an irregular surface and multiple point diffrac-tions, and low seismic penetration due to signal attenuation inthe upper few metres. Moraine is observed as a large depositalong the eastern edge of the main basin (line 2, Fig. 5a), andpossibly draping basement in the northeast corner of the lake(line 2, Fig. 4). Like bedrock, moraine deposits are onlappedby fine-grained sediment.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

LINE 2

0.18

Fig. 4 A, An un-interpreted segment of seismic line 2. The verti-cal exaggeration is *8. B, Interpretation showing location of slumpdeposits into the lake basin, the bedrock and moraine contact withthe overlying lake sediments, and possible structures within theseismic basement. Numbers refer to features described in the text:ml to m5, slump deposits; fl to f3, lake-floor features; bl to b3,features within the basement.

160

Verticalexaggeration

8x

Reflector

_ -> Outline ofx " slump deposit

^ Basement

, . - ' Moraine

,' Inferred fault

Featuresm 13 discussed in

the text

N

Ïo

to

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

Upton & Osterberg—Seismic reflection, L. Tekapo 349

Fig. 5 A, Segment of line 2 nearthe middle of the lake showingmoraine, characterised by a lumpyupper surface and limited penetra-tion. The sediments fill in the to-pography of the moraine but do notdrape over the topographic highs. B,Segment of line 2 near the south endof the lake showing a region of gaswithin the sedimentarypackage. C,Segment of line 5 showing a massflow deposit. Note the disturbedreflectors in this region and thesmooth reflector that overlies thewhole packet.

s140

B0.12

0.14

0.16

mass flow deposit

0.14

0.16

Verticalexaggeration

8x

140

Unit 3—fan and lake fill sequences

This unit includes coarse sediments of the godley and cassRiver deltas and fine-grained varved sediment within thecentral lake basin.

coarse sediment interpreted as sand and gravel is ap-parent at the cass River delta and the upper foreset of thegodley River delta (line 3, Fig. 6). high signal attenuationby the coarse sediment results in limited seismic penetration(c. 30-50 m).

Fine-grained sediment is imaged to depths up to 145 mbelow the lake floor in both basins (e.g., Fig. 4). bedding isgenerally nearly flat lying with uniform, regularly spaced,laminated reflectors, representing the varved silt and muddeposits cored by Pickrill & irwin (1983). Sediment reflec-tors are continuous for several kilometres, except where theyare disturbed by natural gas pockets, basement highs, andinterpreted mass movement deposits (see below) from theflanks of the lake basin. Sediment reflectors have a uniformspacing of c. 1.25 m, which is a seismic interference patterngenerated by the c. 1 cm thick varves. The thinnest unit thatcan be resolved without interference in these seismic profilesis c. 65 cm. The regular pattern of the seismic reflections,however, suggests that the sediment is varved for the entirethickness visible in the profiles.

Natural gas

Pockets of natural gas are common within the varved sedimentthroughout the lake, concentrated in regions undisturbed bythe basement highs and near the two river deltas. Natural gaspockets have a characteristic irregular, diffuse, low-amplitude

reflector with acoustic wipe-out below (line 2, Fig. 5b). Thetops of the gas pockets are generally located at 10-30 mbeneath the lake floor.

Mass movement deposits

Within the varved sediment of Lake Tekapo are regions ofbrighter, disturbed reflectors (e.g., Fig. 5c) that we interpretas mass movement deposits (turbidite deposits). a l l of thedeposits are located adjacent to the steeply sided bedrockexposures along the lake shore or Motuariki Ridge and island,and thus we conclude that the deposits originated from thesehigh-relief regions.

Description of lines (from south to north or west to east)Line 1 (not shown) at the southern end of the lake imagestwo sedimentary basins, filled with flat lying, fine-grained,varved sediment, separated by the southern end of the Mo-tuariki moraine ridge.Line 2 (Fig. 4) lies along the east edge of the lake. a t its south-ern end, flat-lying varved sediments are disturbed in placesby mass-flow deposits and natural gas moving up throughthe sedimentary pile. Near the middle of the lake, line 2 ap-proaches within 500 m of the shore and images moraine alongthe edge of the lake basin. a t the northeast corner of the lake,the record is dominated by three lake-floor highs (f1, f2 andf3) overlying basement highs and folded or draped sediment.f1 is the largest, standing c. 6 m higher than the slope to thenorth of it and c. 12 m above the projection of the lake slopeto the south. The other lake-floor highs are c. 5-6 m above theprojected undisturbed slope of the lake floor. all three overlie

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

350 New Zealand Journal of geology and geophysics, 2007, Vol. 50

w LINE 3

0.08

Verticalexaggeration

8x

lake floor multiple

80

100 £Q.CDQ

1200.16

Seismic basement \ Structure offsettingreflector ? seismic basement

Fig. 6 interpretation of line 3 across the head of the lake. The sediments here are dominated by the delta of the godley River. The topsurface of the seismic basement is offset. it is unclear if this is movement due to faulting or a cut channel which has since been filled inwith laminated sediments.

highs in the seismic basement (b1, b2, b3). basement highb3 appears to be an uplift of bedrock, and b1 and b2 appearto be bedrock highs overlain by moraine. a number of massmovement deposits are recorded in this region.

Line 3 (Fig. 6) runs across the lake near its head. high signalattenuation by the coarse sediment results in limited seismicpenetration (c. 30-50 m). The western half of line 3 revealsbasement greywacke or foreset beds overlain by c. 6 m ofsediment. There is a conspicuous c. 30 m deep offset in thebasement/foreset sediment that has been filled with laminatedsediment. This feature may represent a channel eroded intothe bedrock/older sediment during a lower lake level andsubsequently filled, with possibly two or more cut and fillcycles, or it could be a structural feature such as a fault.

Line 4 (Fig. 7a) runs along the western edge of the lake.From north to south along the western axis of the lake, thelake floor gradually drops, then rises sharply at locality f4.From this high, the lake floor dips gently down to the southinto a deep sediment-filled basin. South of the step in the lakefloor, a bedrock high covered with disturbed sediment reachesto within 15-20 m of the lake floor (b5). a number of reflec-tors are observed within the bedrock, but it is not possible todetermine if these are real reflectors or diffractions. a numberof mass movement deposits occur (m6, m7, m8).

Line 5 (Fig. 8) is dominated by Motuariki Ridge and theMotuariki basin, at >120 m, the deepest part of the lake.A basement high (b7) is west of the ridge. The reflectorslying directly on the basement high are disturbed. The top15-20 m of overlying sediment are less disturbed apart from

an obvious mass movement deposit (m9). There is a bulge inthe lake floor here (f5): it does not correspond to the uplift inthe basement but appears to be draping the underlying massmovement deposit (m9) and mimicking its upper surface. Twodipping reflectors (b8 and b9) are observed in the basement.approximately 145 m of varved lake sediment is imagedbeneath Motuariki basin. Two mass flow deposits, m11 andm12, occur within the top c. 20 m of Motuariki basin fill.Volumes can be estimated where these deposits are imagedon two perpendicular seismic profiles. deposit m1 1 is crossedby line 6 and has a volume of at least 6 × 106m3. deposit m12(also seen on line 2) has a volume of at least 2.4 × 106m3.

Line 6 (Fig. 7b) runs along the central axis of the lake justnorth of Motuariki island. a steep bedrock reflector on thenorthern slope of Motuariki island is onlapped by flat-lyingvarved sediments. Two possible mass movement deposits,m11 and m15, are observed within these sediments. North ofthese deposits, along-strike from the icF, a c. 5 m offset of thelake floor, steep to the north and dipping gently to the south,occurs at locality f7. The offset on the lake floor is associatedwith a bedrock high (b10), which reaches to within c. 20 mof the lake floor. On the south side of the basement high, thereflector is diffuse and may be overlain in places by a thinveneer of moraine. Large amounts of natural gas are seen onthe northern portion of this line.

Lines 7 and 8 (not shown) run across the lake south of line3. They show varved sediments with significant amounts ofnatural gas. No mass movement deposits, basement highs, orlake floor offsets are observed on these lines.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

Upton & Osterberg—Seismic reflection, L. Tekapo 351

INTERpRETATION OF THE SEISMICREFLECTION DATA

Approximate age of reflectorsdating of the reflectors is based on the more recent of twoavailable estimates of sedimentation rate (8 mm/yr; Quinn &Wilson 2004). a n earlier study yielded a faster sedimentationrate (10 mm/yr; Pickrill & irwin 1983). given the uncertainty,we use errors of ±20% when dating features observed in therecord.

Basement highs and lake-floor featuresbasement highs and lake-floor offsets are imaged at thesouthwest and northeast corners of the lake. abasement high(b7) occurs west of Motuariki Ridge on line 5 (Fig. 8). Thereflectors lying directly on the basement high are disturbed,suggesting that the basement high may have pushed up intothese sediments. Two dipping reflectors (b8 and b9) are ob-served in the basement. These features occur along the strikeof the icF to the southwest. They have an apparent dip in theline of c. 30ºe, which gives an actual dip of c. 44ºSe alongthe strike of the icF. along the strike, a prominent jump isobserved at locality f4 (line 4, Fig. 7a). The top four reflectors(representing c. 5 m depth) below locality f4 are unbrokenand follow the lake floor. beneath c. 5 m the reflectors aredisturbed in a steeply dipping region (with a dip of c. 45ºN)above the bedrock basement. a possible north-dipping reflec-tor is seen within the bedrock (b4). along the central axis ofthe lake (line 6, Fig. 7b), just north of Motuariki island, ac. 5 m offset of the lake floor, steep to the north and dippinggently to the south, occurs at locality f7. The offset on the lakefloor is associated with a bedrock high (b10) which reachesto within c. 20 m of the lake floor. These features occur alongthe strike of the icF. The combination of basement highs,disturbed reflectors, and orientations parallel to the icF sug-gest that we are seeing the continuation of the fault withinthe lake basin on lines 4, 5 and 6.

a t the northeast corner of the lake, line 2 is dominatedby three lake-floor highs (f1, f2 and f3) overlying basementhighs and folded or draped sediment (Fig. 4). These featuresall occur along the strike of the active FcF (Fig. 2) (Upton etal. 2003), suggesting that the basement highs and lake-floorfeatures have resulted from movement along this structure.A possible fault occurs between features b1 and b2 (Fig. 4).This feature has an apparent topographic offset with the tophangingwall being lower than the top of the footwall. Wesuggest that this is a combination of structure and glacialerosion, weaker fault rock allowing removal of more of thehangingwall by the glacier.

Topographic highs in a tectonically and glacially activeregion may form constructionally by uplift on a fault, or asroches moutonnées by glacial erosion. alternatively, theymay reflect the interaction of both processes. Roches mouton-nées generally form as a glacier flows over a region of moreresistant bedrock. They are commonly asymmetric, with theup-flow side smooth and relatively gently sloping, and thedown-flow side rough and considerably steeper, a result ofplucking by the ice. bedrock highs on the shores of LakeTekapo, include Mt John, Wee Mcgregor, and Mt hay (Fig. 2,9). The asymmetric profile of Mt John suggests a classicroche moutonnée, however the profiles of the other bedrockhighs are not as indicative (Fig. 9). Wee Mcgregor has asymmetric profile and Mt hay is very steep on its northernslopes and shallower on its southern slope. These differences

may result from the orientation of the foliation relative to theflow direction of the ice. Mt John's foliation is c. 030°, whichis subparallel to the ice-flow direction, whereas Mt hay'sfoliation (c. 090°) is perpendicular to the transport directionof the ice. Motuariki island has been previously mapped as amoraine ridge and as a bedrock ridge (gair 1967; Fox 1987).Lines 5 and 6 from this study show that Motuariki island andthe connected ridge to the north consist mainly of bedrock(Fig. 7b, 8). The island has a gentle northern slope and a steepsouthern slope, suggestive of a roche moutonnée (Fig. 9). Wesuggest that these bedrock highs beneath the subsurface ofLake Tekapo are fault-controlled but are being eroded downevery c. 100 000 yr by glaciers advancing from the Southernalps to give them an appearance similar to a roche mouton-née.

We can approximate how much vertical movement oc-curred on these faults since the Lake Tekapo basin was emp-tied of ice following the LgM at c. 20 ka. displacement rateson these faults are c. 0.5-0.1 mm/yr (James 1998; Upton etal. 2004). Using these two constraints, we make a rough ap-proximation of 10-20 m of possible vertical displacementalong the faults over the last 20 000 yr. a s the bedrock highsare at least 50 m above the lake floor, they must predate thelast glaciation.

Relating onshore and lake basin geologyThe icF and the FcF are parallel but offset from each other.From our seismic sections we can trace the icF into the lakebasin on lines 4,5 and 6, but there is no evidence for it crossingline 2. Line 2 along the strike from the features observed onlines 4,5 and 6 is remarkable for flat-lying, continuous reflec-tors with no basement uplifts. The existence of a fault brecciaalong the strike on the eastern lakeshore (Fig. 3b) suggeststhat the icF may have once extended across what is now thelake basin. We can trace the FcF into the lake basin on line 2,but there is no evidence for them continuing into the westernhalf of the lake. Lines 4 and 6 in the northern lake also showno basement uplifts and flat-lying, continuous reflectors.

does the offset on these faults die out as they go into thelake basin or is there a structure accommodating movementbetween them? between 10 and 20 m of possible uplift sincethe last glaciation is consistent with lake-floor offsets of 12 mat f1 and 5-6 m at f2 and ß on line 2, and suggests that offseton the FcF does not reduce within the lake basin but rathermust stop abruptly between lines 2 and 4. Similarly, lake-flooroffsets of c. 10 m on lines 4 and 6 at the southeast end of thelake are consistent with uplift on the icF continuing into thelake and stopping abruptly between lines 2 and 6. We proposea structure running the length of the lake against which theicF and the FcF end (Fig. 10). We did not image offset on anyof our across-lake lines, implying that this structure has notbeen active since the last glaciation. Our proposed structuremay be the Tekapo River Fault (Fig. 10), a northwest dippingthrust with c. 3 km of throw from which the icF would bean oblique backthrust, inferred by Long et al. (2003) from aseismic study.

Coeval mass movement depositsMass movement deposits m6, m7, m8 (Fig. 7a), m9, m10,m1 1 and m12 (Fig. 7b, 8) are all overlain by the reflector 11(counting down from the lake floor), implying that they arecoeval. Using the interval of 1.25 m per reflector describedabove and the sedimentation rate of 8 mm/yr (Quinn & Wilson2004), these deposits can be dated at c. 1720 ± 344 yr bP.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

0.22

BLINE 6

0.16

f7 120

Verticalexaggeration

8x

seafloor/multiple

_ ', Outline ofslumpdeposit

s Basementf reflector

_• Inferredfaults

Featuresm13 discussed

in the text

Vo

N

o

Fig. 7 A, Interpretation of a segment of line 4. Vertical exaggeration is *8. Bedrock outcrops are outlined in solid line. Dashed line is believed to be the top surface of moraine, possibly connectedto the moraine ridge north of Motuariki Island. Numbers refer to features described in the text: m6 to m8, slump deposits; f4, lake-floor feature; b4 to b5, features within the basement. B, Interpretedsection of line 6. mi l to ml5, slump deposits; f7, lake-floor feature; blO, feature within the basement. Symbols as for (A). IFig. 8 (below) A, An un-interpreted segment of seismic line 5. The vertical exaggeration is *8. B, Interpretation showing location of slump deposits into the lake basin, the bedrock, and morainecontact with the overlying lake sediments, and possible structures within the seismic basement. Numbers refer to features described in the text: m9 to ml4, slump deposits; £5 to f6, lake-floor fea-tures; b7 to b9, features within the basement.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

0.22-

B

0.12-

W

SO.14-0

|

t 0.16-

£0.18-

§0.20-

0.22-

•Motuariki Ridge

f5

-100

-120,

Verticalexaggeration

8x

0Q

^ Reflector

_ -̂ Outline ofx " slump

deposit

/S Basement

-140Q . - - ' Moraine

y Inferred' ' faults

" 1 6 0 Featuresml discussed

in the text

II00

o

I§•

I

\

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

354 New Zealand Journal of geology and geophysics, 2007, Vol. 50

Line 2

Motuariki Island

Line 6

MtJohn

Line 4

Wee McGregor

MtHay Old Man Range Olo l

1 km

IrishmanCreekFault

vertical exaggeration5x

Fig. 9 Profiles of topographichighs within the lake basin andsurrounding Lake Tekapo. all arecomposed of bedrock except theOld Man Range, which is madeup of Pliocene-Pleistocene can-nington gravels. all profiles areshown from north to south, the as-sumed direction of ice flow duringthe glacial highs. all profiles areat the same scale with a verticalexaggeration of ×5.

The higher sedimentation rate of Pickrill & irwin (1983)would give a date of 1370 ± 274 yr bP. in the northeasternpart of the lake (line 2, Fig. 4), three mass movement deposits(m1, m2, m3) appear to be coeval and are overlain by the18th reflector. Quinn & Wilson's (2004) sedimentation rateof 8 mm/yr yields an age of c. 2810 ± 562 yr bP for thisevent. given the similar stratigraphic age of these two setsof deposits, we suggest that they may have been triggered byearthquakes, similar to deposits which have been describedin Lake Lucerne, Switzerland (Schnellmann et al. 2002) andin canada (Shilts & clague 1992; Shilts et al. 1992). We donot discount that the other mass movement deposits mighthave been formed by earthquakes; however, without otherdeposits overlain by the same reflector, it is equally likelythat they are isolated events.

Lake Tekapo is located within 60 km of the alpine Fault,and many other active faults are mapped within 200 kmof the lake (Fig. 1, 2). The closest known active faultsare the icF (McSaveney 1991) and the FcF (Upton etal. 2004). Seismic events recorded in Lake Tekapo couldrepresent either local earthquakes or a larger, more distantearthquake on the alpine Fault or the Marlborough FaultSystem. Quinn (2004) described sandy turbidite layers thatare coarser grained than the surrounding sediment, fromcores L-1397 and L-1398 (Fig. 2). The sandy layers arec. 8-10 cm thick. Quinn (2004) attributed these sandy layersto earthquake-triggered mass flows. her age model placesthese earthquakes in the 1800s and possible events includethe 1848 Mw 7.5 earthquake in Marlborough, the 1868 Mw

7.5 earthquake at cape Farewell, the 1888 Mw 7.3 earthquakein North canterbury, and the 1893 Mw 6.9 earthquake atNelson (gNS Science database). Weathering-rind dating byMcSaveney (1991) suggests four major events on the icFin the last 5160 ± 360 yr, suggesting a recurrence intervalof movement of 1290 ± 90 yr. The mass movement recordcontained in our seismic survey at the southern end of thelake suggests at least one event around 1720 ± 344 yr bP.Relating these mass movement deposits to an icF ruptureis consistent with McSaveney's (1991) dating. The massmovement deposits recorded in our seismic survey havevolumes in the order of 6 × 106m3, considerably larger thanthe volume of the sandy layers observed in the record of the

last 300 yr (Quinn 2004). Thus, if these mass movementdeposits were triggered by a distant earthquake, the intensityfelt in the Tekapo region must have been greater than thatfelt during the 1800s events. The epicentre of a large alpineFault event would be considerably closer to Lake Tekapo(<100 km) than any of the events mentioned above, andpaleoseismic studies suggest that such an event could havea magnitude of c. 7.9 (Sutherland et al. 2007). Paleoseismicstudies provide evidence for alpine Fault events in the last1000 yr, at c. a d 1717, 1620, and 1450 (Wells et al. 1999).These are all more recent than the most recent event werecord; however, we cannot be certain that we would recordevery major event with our sparse 1 km grid.

SUMMARY

The lacustrine deposits of the Lake Tekapo basin provide uswith an c. 16-20 000 yr record of paleoseismic and tectonicevents in the central Southern alps.1. evidence of recent (post-LgM) movement on both the

icF and FcF is seen in the high-resolution seismic re-flection record from Lake Tekapo in the form of bedrockuplifts, folded sediment layers, and lake-floor offsets(Fig. 10).

2. Lake-floor offsets in the order of 10-20 m are compat-ible with uplift rates on these faults of 0.5-1.0 mm/yrdetermined from other studies.

3. both active faults appear to continue into the lake basinbut neither extends to the opposite shore (Fig. 10). Wepropose the existence of a north-south-oriented structurerunning the length of the lake basin, possibly the TekapoRiver Fault of Long et al. (2003).

4. Mass movement deposits occur within the sedimentaryfill. We suggest that these represent mass movementevents triggered either by local earthquakes on the icFand FcF or more distant alpine Fault or MarlboroughFault System earthquakes.

5. Using a sedimentation rate of 8 mm/yr, we date two setsof mass flow deposits at 1720 ± 78 yr bP and 2810 ± 78yrbP.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

Upton & Osterberg—Seismic reflection, L. Tekapo 355

Anticline

Syncline

Fault gouge

Indurated fault rocks -

.---' Active faults (barbs onupthrown side)

, - Inferred active structures

- ' Inferred inactive structures

Fig. 10 The study area showing sub-bottom features imaged bythe seismic survey.

ACKNOWLEDGMENTS

Discussions with Dave Craw, Chuck Landis, Peter Koons, GaryWilson, Allisa Quinn, David Barrell, and Simon Cox helped developand refine the ideas expressed herein. Brian Grant and Mike Trinderare thanked for technical assistance, collecting, and analysing theseismic data. Field assistance was ably provided by Juliet Harrisand Belinda Mellish. Detailed reviews by Mauri McSaveney andJohn Clague improved the manuscript. This research was supportedfinancially by the University of Otago and the Foundation ofResearch, Science and Technology (Contract UO0818). GeographXis acknowledged for the digital elevation map used in Fig. 1.

REFERENCES

Becker JA, Craw D 2000. Structure and neotectonics on the MainDivide, upper Wilberforce valley, mid Canterbury, NewZealand. New Zealand Journal of Geology and Geophysics43: 228-217.

Chetwin E 1998. Active faulting and subsurface structure in theMackenzie basin: an investigation using gravity and seis-mics. Unpublished BSc (Hons) thesis, Victoria Universityof Wellington, Wellington, New Zealand.

Cox SC, DJA Barrell 2007. Geology of the Aoraki area. Institute ofGeological & Nuclear Sciences 1:250 000 Geological Map15. 1 sheet + 71 p. Lower Hutt, New Zealand, Institute ofGeological & Nuclear Sciences.

Cox SC, Findlay RH 1995. The Main Divide Fault Zone and itsrole in formation of the Southern Alps, New Zealand. NewZealand Journal of Geology and Geophysics 38: 489-499.

DeMets CR, Gordon G, Argus DF, Stein S 1994. Effect of recentrevisions to the geomagnetic reversal time scale on estimatesof current plate motions. Geophysical Research Letters 21 :2191-2194.

Field BD, Browne GH 1986. Lithostratigraphy of Cretaceous andTertiary rocks, southern Canterbury, New Zealand. NewZealand Geological Survey Record 14. 55.

Fox AN 1987: The neotectonics history of the Lake Tekapo region,MacKenzie Basin, New Zealand. Unpublished MSc thesis,University of Canterbury, Christchurch, New Zealand.

Gair HS 1967. Sheet 20—Mt Cook. Geological map of New Zealand1:250 000. New Zealand Geological Survey.

Gair HS 1978. Mid and South Canterbury and North Otago. In:Suggate RP ed. The geology of New Zealand Vol 2. Pp.510-516.

Haines AJ, Calhaem IM, Ware DE 1979. Crustal seismicity nearLake Pukaki, South Island. In: Walcott RI, Cresswell MMed. The origin of the Southern Alps. Royal Society of NewZealand Bulletin 18: 87-94.

Irwin J 1970a. Lake Ohau provisional bathymetry 1:31 680. NewZealand Oceanographic Institute Chart, Lake Series.

Irwin J 1970b. Lake Pukaki provisional bathymetry 1:31 680. NewZealand Oceanographic Institute Chart, Lake Series.

Irwin J 1973. Lake Tekapo bathymetry 1:31 680. New ZealandOceanographic Institute Chart, Lake Series.

Irwin J 1978. Bottom sediments of Lake Tekapo compared with ad-jacent Lakes Pukaki and Ohau, South Island, New Zealand.New Zealand Journal of Marine and Freshwater Research12: 245-250.

James Z 1998. Geology, Quaternary structure, fault rocks and fluidflow, Fox Peak Range, eastern Southern Alps. UnpublishedMSc thesis, University of Otago, Dunedin, New Zealand.

Kleffmann S 1999. Crustal structure studies of a transpressionalplate boundary—the central South Island of New Zealand.Unpublished PhD thesis, Victoria University of Wellington,Wellington, New Zealand.

Leitner B, Eberhart-Philips D, Anderson H, Nabelek JL 2001. Afocused look at the Alpine Fault, New Zealand: seismic-ity, focal mechanisms, and stress observations. Journal ofGeophysical Research 106: 2193-2220.

Long DT, Cox SC, Bannister S, Gerstenberger MC, Okaya D 2003.Upper crustal structure beneath the eastern Southern Alpsand the Mackenzie Basin, New Zealand, derived from seis-mic reflection data. New Zealand Journal of Geology andGeophysics 46: 21-39.

McSaveney MJ 1991. Paleoseismicity of the Irishman Creek Fault byweathering-rind dating. Geological Society of New ZealandMiscellaneous Publication 59A.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14

356 New Zealand Journal of Geology and Geophysics, 2007, Vol. 50

Norris RJ, Cooper AF 2001. Late Quaternary slip rates and slippartitioning on the Alpine Fault, New Zealand. Journal ofStructural Geology 23: 507-520.

Norris RJ, Koons PO, Cooper AF 1990. The oblique-convergent plateboundary in the South Island of New Zealand: implicationsfor ancient collision zones. Journal of Structural Geology12: 715-725.

Pickrill RA, Irwin J 1983. Sedimentation in a deep glacier-fed lake—Lake Tekapo, New Zealand. Sedimentology 30: 63-75.

Quinn AN 2004. High resolution environmental magnetism ofshort sediment cores from Lake Tekapo, New Zealand. Un-published PGDipSci thesis, University of Otago, Dunedin,New Zealand.

Quinn AN, Wilson GS 2004. High resolution environmental mag-netism of short sediment cores from Lake Tekapo, NewZealand. Geological Society of New Zealand MiscellaneousPublication 117A.

Reyners M 1988. Reservoir induced seismicity at Lake Pukaki, NewZealand. Geophysical Journal International 93: 127-135.

Schnellmann M, Anselmetti FS, Giardini D, McKenzie JA, Ward SN2002. Prehistoric earthquake history revealed by lacustrineslump deposits. Geology 30: 1131-1134.

Shilts WW, Clague JJ 1992. Documentation of earthquake-induceddisturbance of lake sediments using subbottom acoustic pro-filing. Canadian Journal of Earth Sciences 29: 1018-1042.

Shilts W, Rappol WM, Biais A 1992. Evidence of late and postglacialseismic activity in the Témiscouata-Madawaska Valley,Quebec-New Brunswick, Canada. Canadian Journal of EarthSciences 29: 1043-1069.

Smith DW, Craw D, Koons PO 1996. Tectonic hydrothermal goldmineralisation in the outboard zone of the Southern Alps,New Zealand. New Zealand Journal of Geology and Geo-physics 39: 201-209.

Suggate RP, Almond PC 2005. The last glacial maximum (LGM)in western South Island, New Zealand: implications for theglobal LGM and MIS 2. Quaternary Science Reviews 24:1923-1940.

Sutherland R 1999. Cenozoic bending of New Zealand basementterranes and Alpine Fault displacement: a brief review.New Zealand Journal of Geology and Geophysics 42:295-301.

Sutherland R, Eberhart-Phillips D, Harris RA, Stern T, Beavan J,Ellis S, Henrys S, Cox S, Norris RJ, Berryman KR, TownendJ, Bannister S, Pettinga J, Leitner B, Wallace L, Little TA,Cooper AF, Yetton M, Stirling M 2007. Do great earthquakesoccur on the Alpine fault in central South Island, NewZealand? In: Okaya D, Stern T, Davey, F ed. Geotectonicinvestigation of a modern continent-continent collisionalorogen: Southern Alps, New Zealand. American GeophysicalUnion, Geographical Monograph 175.

Templeton AS, Chamberlain CP, Koons PO, Craw D 1998a. Stableisotopic evidence for mixing between metamorphic fluidsand surface-derived waters during recent uplift of theSouthern Alps, New Zealand. Earth and Planetary ScienceLetters 154: 73-92.

Templeton AS, Craw D, Koons PO, Chamberlain CP 1998b. Near-surface expression of a young mesothermal gold mineral-izing system, Sealy Range, Southern Alps, New Zealand.Mineralium Deposita 34: 163-172.

Upton P, Craw D, Caldwell TG, Koons PO, James Z, WannamakerPE, Jiracek GJ, Chamberlain CP 2003: Upper crustal fluidflow in the outboard region of the Southern Alps, New Zea-land. Geofluids 3: 1-12.

Upton P, Craw D, James Z, Koons PO 2004. Structure and neotecton-ics of the Southern Two Thumb Range, mid-Canterbury, NewZealand. New Zealand Journal of Geology and Geophysics47: 141-153.

Walcott RI 1978. Present tectonics and late Cenozoic evolution ofNew Zealand. Geophysical Journal of the Royal Astronomi-cal Society 52: 137-164.

Wells A, Yetton MD, Duncan RP, Stewart GH 1999. Prehistoric datesof the most recent Alpine Fault earthquakes, New Zealand.Geology 27: 995-998.

Dow

nloa

ded

by [

UO

V U

nive

rsity

of

Ovi

edo]

at 1

0:33

13

Nov

embe

r 20

14