The record of earthquakes in India is patchy prior to 1800 and its improvement is much impeded by its dispersal in a dozen local languages, and several colonial archives. Although geological studies will necessarily complement the historical record, only two earthquakes of the dozens of known historic events have resulted in surface ruptures, and it is likely that geological data in the form of liquefaction features will be needed to extend the historic record beyond the most recent few centuries. Damage from large Himalayan earthquakes recorded in Tibet and in northern India suggests that earthquakes may attain M=8.2. Seismic gaps along two-thirds of the Himalaya that have developed in the past five centuries, when combined with geodetic convergence rates of approximately 1.8m/century, suggests that one or more M=8 earthquakes may be overdue. The mechanisms of recent earthquakes in Peninsular India are consistent with stresses induced in the Indian plate flexed by its collision with Tibet. A region of abnormally high seismicity in western India appears to be caused by local convergence across the Rann of Kachchh and possibly other rift zones of India. Since the plate itself deforms little, this deformation may be related to incipient plate fragmentation in Sindh or over a larger region of NW India.
Conclusions of study of Indian tectonic Movements by Roger Bilham
CIRES & Geological Sciences
University of Colorado Boulder CO 80309-0399
Bilham, R., Earthquakes in India and the Himalaya: tectonics, geodesy and history, (2004)Annals of Geophysics
The tectonic setting of India's collision with Asia is now reasonably well characterized from recent seismicity and geodetic studies of relative motion at their plate boundaries. Direct measurements across and within the Himalaya reveal a locking line beneath the edge of the Tibetan Plateau and the absence of creep to its south (Bilham et al, 1995; 1998; 2001), implying that the advance of the Himalaya over the Indian plate proceeds largely through the recurrence of great plate boundary earthquakes.
Earthquakes within the Indian Plate are attributable to the superposition of the NW compressional stress of collision, on the stresses arising from plate flexure. The depth and mechanisms of recent earthquakes reflect the sense of these combined stresses.
A several millennia-long written record in India has revealed few major earthquakes prior to the past two centuries. This is partly due to the fact that extant records have yet to be searched rigorously for earthquakes, but is in part due to the corruption of potentially valuable records and their loss through fire, war and decay. Despite their sparseness it is likely that documents on historic earthquakes will surface in Tibetan, Urdu and Arabic records that will change current estimates of the significance of seismic gaps in the Himalaya, and may change our understanding of earthquakes within the Indian continent.
Our current understanding of Himalayan earthquakes is such that we may calculate potential slip in several segments of the plate boundary, but we cannot estimate the timing of future events. Making assumptions about the probable completeness of the historic seismic record we can estimate relative seismic hazard, or we can estimate minimum slip potential based on the time since the last known earthquake (Bilham et al., 2001). This has moderate relevance to planning for future earthquakes. The eventual establishment of recurrence intervals for Himalayan ruptures will require a combination of serendipitous historical studies and geological trench investigations of faulting and earthquake-induced liquefaction features.
Courtesy:
CIRES & Geological Sciences
Conclusions of study of Indian tectonic Movements by Roger Bilham
CIRES & Geological Sciences
University of Colorado Boulder CO 80309-0399
Bilham, R., Earthquakes in India and the Himalaya: tectonics, geodesy and history, (2004)Annals of Geophysics
The tectonic setting of India's collision with Asia is now reasonably well characterized from recent seismicity and geodetic studies of relative motion at their plate boundaries. Direct measurements across and within the Himalaya reveal a locking line beneath the edge of the Tibetan Plateau and the absence of creep to its south (Bilham et al, 1995; 1998; 2001), implying that the advance of the Himalaya over the Indian plate proceeds largely through the recurrence of great plate boundary earthquakes.
Earthquakes within the Indian Plate are attributable to the superposition of the NW compressional stress of collision, on the stresses arising from plate flexure. The depth and mechanisms of recent earthquakes reflect the sense of these combined stresses.
A several millennia-long written record in India has revealed few major earthquakes prior to the past two centuries. This is partly due to the fact that extant records have yet to be searched rigorously for earthquakes, but is in part due to the corruption of potentially valuable records and their loss through fire, war and decay. Despite their sparseness it is likely that documents on historic earthquakes will surface in Tibetan, Urdu and Arabic records that will change current estimates of the significance of seismic gaps in the Himalaya, and may change our understanding of earthquakes within the Indian continent.
Our current understanding of Himalayan earthquakes is such that we may calculate potential slip in several segments of the plate boundary, but we cannot estimate the timing of future events. Making assumptions about the probable completeness of the historic seismic record we can estimate relative seismic hazard, or we can estimate minimum slip potential based on the time since the last known earthquake (Bilham et al., 2001). This has moderate relevance to planning for future earthquakes. The eventual establishment of recurrence intervals for Himalayan ruptures will require a combination of serendipitous historical studies and geological trench investigations of faulting and earthquake-induced liquefaction features.
Courtesy:
CIRES & Geological Sciences
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