Lecture 7 Reverse faults and folds I

Environments Orthogonal convergence –Himalaya –Zagros –Caucasus

Caucasus Zagros, Elborz, etc Himalaya

Earthquakes

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 North Tehran Fault

Caucasus Zagros, 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 ( ) (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

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