seismic hazard analysis for guam & the northern mariana islands
DESCRIPTION
Seismic Hazard Analysis for Guam & the Northern Mariana Islands. Chuck Mueller U.S. Geological Survey Golden, Colorado, USA. Tectonic Setting & Seismic History. Westward subduction of Pacific plate at Mariana Trench Back-arc spreading at Mariana Trough Complex oblique deformation in south. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/1.jpg)
Seismic Hazard Analysisfor Guam & the Northern Mariana
Islands
Chuck MuellerU.S. Geological SurveyGolden, Colorado, USA
![Page 2: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/2.jpg)
Tectonic Setting&
Seismic History
![Page 3: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/3.jpg)
Westward subduction of Pacific plate at Mariana Trench
Back-arc spreading at Mariana Trough
Complex oblique deformation in south
![Page 4: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/4.jpg)
![Page 5: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/5.jpg)
Northern & central subduction zone:
Deep seismicity (down to 700km)
Steeply dipping Benioff zone
![Page 6: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/6.jpg)
Southern subduction zone:
Less deep; less steep
![Page 7: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/7.jpg)
Largest modern eqks with likely shallow thrust mechanisms:
06Jun1993, MW6.4
14Aug2002, MW6.5
No very large eqk has ever been associated with the Mariana interface!
![Page 8: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/8.jpg)
08Aug1993, MW7.8
Harada & Ishibashi (2008): faulting on sub-horizontal plane ~70km deep within the subducting slab
![Page 9: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/9.jpg)
Largest Observed (MW)
Depth (km) 1900-2011 1964-2011
0-40 mt 7.3 (1940) 6.5 (2002)
0-40 or 7.4 (1990)
0-40 other 7.5 (1902) 6.9 (2007)
41-80
81-120
121-160
161-200
201-300
301-500
501-700
Historical earthquakes
shallow
Benioff
![Page 10: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/10.jpg)
Largest Observed (MW)
Depth (km) 1900-2011 1964-2011
0-40 mt
0-40 or
0-40 other
41-80 7.8 (1993)
81-120 8.2 (1914) 7.6 (2000)
121-160 6.8 (1957) 6.6 (2005)
161-200 7.0 (1931) 6.9 (1953)
201-300 7.5 (2007)
301-500 7.1 (1905) 6.5 (2001)
501-700 7.1 (1995)
Historical earthquakes
shallow
Benioff
![Page 11: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/11.jpg)
1) Gridded Historical Seismicity
![Page 12: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/12.jpg)
Source catalogs:
1) EVC
2) PDE
3) ISC
Decluster with G&K
![Page 13: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/13.jpg)
Divide declustered catalog into eight sub-catalogs:• 0-40 km (megathrust, outer-rise, “other”)• 41-80• 81-120• 121-160• 161-200• 201-300• 301-500• 501-700
![Page 14: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/14.jpg)
![Page 15: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/15.jpg)
![Page 16: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/16.jpg)
2-D Gaussian Smoothing• 50-km for shallow• 30-km for deeper
![Page 17: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/17.jpg)
![Page 18: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/18.jpg)
![Page 19: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/19.jpg)
Largest Observed (MW) Model Parameters
Depth (km)
1900-2011 1964-2011 b Mmin MmaxModel depth
0-40 mt 7.3 (1940) 6.5 (2002)
1.06
5.0
7.0
200-40 or 7.4 (1990)
7.5 (80%)
8.2* (20%)
0-40 other
7.5 (1902) 6.9 (2007) 7.5
41-80 7.8 (1993)
8.2
60
81-120 8.2 (1914) 7.6 (2000) 100
121-160 6.8 (1957) 6.6 (2005) 140
161-200 7.0 (1931) 6.9 (1953) 180
201-300 7.5 (2007)
0.80 8.0
250
301-500 7.1 (1905) 6.5 (2001) 400
501-700 7.1 (1995) 600* Mmax from Am Samoa
Historical earthquakes and seismicity hazard models
![Page 20: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/20.jpg)
Ground Motions for Background SeismicityShallow (0-40):• NGA B&A (0.167)• NGA C&B (0.167)• NGA C&Y (0.167)• Zhao crustal (0.5)Deep (41-700):• Zhao in-slab + epistemic (0.70 as-published + 0.30 adjusted)
![Page 21: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/21.jpg)
2) Megathrust Interface
![Page 22: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/22.jpg)
Megathrust modeling issues
1) Limited seismic history complicates estimates of maximum magnitude. Use MW8 based on local history (80%) and MW9 from other subduction zones (20%).
2) Evidence for weak coupling precludes estimating rates of large earthquakes from plate-motion data. Instead, extrapolate rates of historical earthquakes associated with the megathrust => MW8+ eqk every 450 yrs.
2) 3) Define downdip edge of megathrust surface as 40-km depth contour on west-dipping seismicity. This closely matches Hayes etal Slab1.0. Support for choice of 40 km from co-seismic slip patterns in recent great eqks and depths of thrust-mechanism eqks along Izu-Bonin (Hayes).
![Page 23: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/23.jpg)
Conventional wisdom…
Weak plate coupling & weak seismicity on the interface correlate with…
Extension in the upper plate
Active back-arc spreading
Weak/no accretion
Deep trench
Old subducting plate
Slow subduction
Steep Benioff zone
![Page 24: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/24.jpg)
Ruff & Kanamori (1980)
![Page 25: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/25.jpg)
Uyeda & Kanamori (1979)
![Page 26: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/26.jpg)
Mariana megathrust Mmax?
Based on its weak seismic history and the
traditional classifications, it would have been
difficult to justify an upper magnitude greater
than about MW 8 for the interface model prior
to 2004 Sumatra and 2011 Tohoku ...
![Page 27: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/27.jpg)
Stein & Okal on the 2004 Sumatra-Andaman earthquake:
“The December earthquake was much larger than expected from a previously proposed relation, based on the idea of seismic coupling, in which such earthquakes occur only when young lithosphere subducts rapidly. Moreover, a global reanalysis finds little support for this correlation. Hence, we suspect that much of the apparent differences between subduction zones, such as some trench segments but not others being prone to MW > 8.5 events … may reflect the short earthquake history sampled.”(BSSA, Jan2007)
![Page 28: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/28.jpg)
Mw 8+ ~ 450 years
![Page 29: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/29.jpg)
Ground Motions for Megathrust Interface
• Zhao interface + epistemic
![Page 30: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/30.jpg)
3) Two Crustal Faults on Guam
![Page 31: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/31.jpg)
Based primarily on Tracy et al. (1964)
![Page 32: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/32.jpg)
Ground Motions for Crustal
Faults
• NGA B&A (0.333)
• NGA C&B (0.333)
• NGA C&Y (0.333)
![Page 33: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/33.jpg)
Results
![Page 34: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/34.jpg)
![Page 35: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/35.jpg)
![Page 36: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/36.jpg)
![Page 37: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/37.jpg)
Guam (Agana) Saipan
2% in 50y
10% in 50y
2% in 50y
10% in 50y
PGA 0.94 0.49 0.57 0.29
0.2sSA 2.86 1.43 1.75 0.83
1.0sSA 0.61 0.30 0.37 0.18
Probabilistic ground motions (g)
![Page 38: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/38.jpg)
![Page 39: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/39.jpg)
![Page 40: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/40.jpg)
![Page 41: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/41.jpg)
![Page 42: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/42.jpg)
![Page 43: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/43.jpg)
Extra slides
![Page 44: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/44.jpg)
![Page 45: Seismic Hazard Analysis for Guam & the Northern Mariana Islands](https://reader036.vdocuments.mx/reader036/viewer/2022081513/56814580550346895db2595a/html5/thumbnails/45.jpg)