Earthquake Geology Along the Himalayan Frontal Thrust of India: Insight to Mechanics Earthquakes Along a Continental Convergent Plate Boundary

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

The Indian-Eurasian plate boundary is the world's type example of continental convergence. The ongoing convergence between India and Eurasia has resulted in the globes's highest mountain range and the largest recorded intracontinental earthquakes on record. The largest of these events have occurred along the Himalayan frontal thrust. The Himalayan frontal thrust extends continuously along the 2500 km length of the Himalayan arc. The Himalayan frontal thrust manifests itself along strike as relatively short and discontinuous range front scarps that cut late Pleistocene and Holocene fluvial terraces and alluvial fans. This project, carried out in collaboration with scientists from the Wadia Institute in India and supported by NSF's Division of Earth Sciences and Office of International Science and Engineering, is conducting field studies along the Himalayan arc to define the timing, size, and lateral extent of earthquake ruptures along the Himalayan frontal thrust fault in India. Structural, stratigraphic, pedogenic, and radiocarbon studies of exposures resulting from the excavation of trenches across fault scarps of the Himalayan frontal thrust fault at 9 sites along the length of the arc in order to provide observational constraints on mechanical models of the earthquake process and the level of seismic hazard imposed by large earthquakes along the Himalayan front. Because the entirety of the India-Eurasia plate boundary is above sea level, the potential exists here to define the spatial, temporal, and surficial, characteristics of accumulated crustal strain that is released in earthquakes along the entirety of a major convergent plate boundary, in a manner and detail not possible along the world's oceanic convergent plate boundaries where the thrust boundary is beneath water. The proposed research is to apply geological techniques to extract information of the size and frequency of occurrence of great earthquakes along the Himalayan frontal thrust fault of India. The Himalayan frontal thrust fault bounds the southern front of the Himalaya. It is the displacements on this fault that have produced a number of the largest continental earthquakes recorded historically and through repeated occurrence through time responsible for the uplift of the Himalaya. The most densely populated regions of India now stretch along the southern edge of the Himalayan frontal thrust. Knowledge of the size and occurrence rate of great earthquakes along the thrust is required for educating the public and providing government agencies the information needed to make prudent planning decisions to mitigate the potential financial and loss-of-life risks along the front in the event of such an earthquake. The information gained by this research will also place observational bounds on the mechanics of the earthquake process along thrust faults, knowledge that may then be applied to seismic hazard analysis in western North America and elsewhere around the globe.