lecture 7 reverse faults and folds i. environments orthogonal convergence –himalaya –zagros...
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Lecture 7
Reverse faults and folds I
Environments
• Orthogonal convergence– Himalaya– Zagros– Caucasus
CaucasusZagros, Elborz, etc
Himalaya
Earthquakes 1962-2003
Indian plate
Eurasian plate
African plate
Arabian plate
Elborz
Kopet Dagh
Greater Caucasus
Zagros
Lesser Caucasus
Himalaya
Earthquakes
J. Hollingsworth & M.J. Bolourchi
Tehran
J. Hollingsworth & M.J. Bolourchi
Tehran
NorthTehranFault
CaucasusZagros, Elborz, etc
Himalaya
Sub-Himalaya
Lesser-Himalaya
High-Himalaya Tibet
Gangetic plain
Topographic profile and simplified geological cross section across the
Himalaya of central Nepal.(Lave and Avouac, 2000)
A deep structure constrained from structural geology, seismic
profiles, gravity and MT sounding.
all thrust faults seem to sole at depth into the MHT
(Avouac, 2003)
Abandoned Fluvial Terraces along Trisuli River
Determining active fold growth from abandoned
river terraces
(Lave and Avouac, 2000)
Holocene slip rate on MFT : 21 +/- 1.5 mm/yr
(Lave and Avouac, 2000)
Over the long-term, shortening across the Central Nepal Himalaya is absorbed by 21 +/- 1.5 mm/yr of thrusting along a single
fault the MFT-MHT
(Cattin and Avouac, 2000)
21 +/-1.5 mm/yr
The pattern of uplift derived from incision rates, is consistent with thrusting over a mid-crustal ramp at front of the higher Himalaya. This zone of localized uplift prevents rapid headward reatreat of sream profile so that the front of the Higher Himalayan can remain linear in map view.
(Lave and Avouac, 2001)
Seismicity of Nepal Himalaya (1995-2000) (DMG)
Environments
• Orthogonal convergence• Behind-the-arc contraction zones
– Tien Shan– Andes– Papua New Guinea and Irian Jaya– Eastern Indonesia– North-Panama deformed belt– Northeastern Japan
Tien Shan
Environments
• Orthogonal convergence• Behind-the-arc contraction zones• Auxiliary faults in strike-slip systems– Coast and Transverse ranges, California
– New Zealand– Qilianshan, China
Transpressional
Transtensional
From the Southern California Integrated GPS Network, courtesy of Ken Hudnut
GPS display a component of strain not parallel to the San Andreas fault. This is accommodated mostly by thrust faults in the LA region.
Most topography in the region is the result of activity on these thrust faults
From JPL’s SRTM mission
For example, the 1987 and 1994 earthquakes alerted us to the presence of active blind thrusts within the metro region
1994
1987
Reverse faults also exist on the north side of the SA fault
Environments
• Orthogonal convergence• Behind-the-arc contraction zones• Auxiliary faults in strike-slip systems
• Shields– Australia– eastern Canada– India
Latur, India, 1993