Paleoseismological evidence of surface faulting along the northeastern Himalayan front, India: Timing, size, and spatial extent of great earthquakes

The similar to 2500 km long Himalayan arc has experienced three large to great earthquakes of M-w 7.8 to 8.4 during the past century, but none produced surface rupture. Paleoseismic studies have been conducted during the last decade to begin understanding the timing, size, rupture extent, return period, and mechanics of the faulting associated with the occurrence of large surface rupturing earthquakes along the similar to 2500 km long Himalayan Frontal Thrust (HFT) system of India and Nepal. The previous studies have been limited to about nine sites along the western two-thirds of the HFT extending through northwest India and along the southern border of Nepal. We present here the results of paleoseismic investigations at three additional sites further to the northeast along the HFT within the Indian states of West Bengal and Assam. The three sites reside between the meizoseismal areas of the 1934 Bihar-Nepal and 1950 Assam earthquakes. The two westernmost of the sites, near the village of Chalsa and near the Nameri Tiger Preserve, show that offsets during the last surface rupture event were at minimum of about 14 m and 12 m, respectively. Limits on the ages of surface rupture at Chalsa (site A) and Nameri (site B), though broad, allow the possibility that the two sites record the same great historical rupture reported in Nepal around A.D. 1100. The correlation between the two sites is supported by the observation that the large displacements as recorded at Chalsa and Nameri would most likely be associated with rupture lengths of hundreds of kilometers or more and are on the same order as reported for a surface rupture earthquake reported in Nepal around A.D. 1100. Assuming the offsets observed at Chalsa and Nameri occurred synchronously with reported offsets in Nepal, the rupture length of the event would approach 700 to 800 km. The easternmost site is located within Harmutty Tea Estate (site C) at the edges of the 1950 Assam earthquake meizoseismal area. Here the most recent event offset is relatively much smaller (<2.5 m), and radiocarbon dating shows it to have occurred after A.D. 1100 (after about A.D. 1270). The location of the site near the edge of the meizoseismal region of the 1950 Assam earthquake and the relatively lesser offset allows speculation that the displacement records the 1950 M-w 8.4 Assam earthquake. Scatter in radiocarbon ages on detrital charcoal has not resulted in a firm bracket on the timing of events observed in the trenches. Nonetheless, the observations collected here, when taken together, suggest that the largest of thrust earthquakes along the Himalayan arc have rupture lengths and displacements of similar scale to the largest that have occurred historically along the world's subduction zones.

[1]  Jing-nan Liu,et al.  Present-Day Crustal Deformation in China Constrained by Global Positioning System Measurements , 2001, Science.

[2]  D. Schelling,et al.  Thrust tectonics, crustal shortening, and the structure of the far-eastern Nepal Himalaya , 1991 .

[3]  R. Bürgmann,et al.  The motion and active deformation of India , 2001 .

[4]  A. Gansser.  Geology of the Himalayas , 1964 .

[5]  P. Molnar,et al.  Cenozoic Tectonics of Asia: Effects of a Continental Collision: Features of recent continental tectonics in Asia can be interpreted as results of the India-Eurasia collision. , 1975, Science.

[6]  Jérôme Lavé,et al.  Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal , 2000 .

[7]  R. Bürgmann,et al.  Kinematics of the India-Eurasia collision zone from GPS measurements , 1999 .

[8]  T. Nakata.  Geomorphic History and Crustal Movements of the Foot-Hills of the Himalayas , 1972 .

[9]  Rebecca Bendick,et al.  Geodetic constraints on the translation and deformation of India: implications for future great Himalayan earthquakes , 1998 .

[10]  W. Szeliga,et al.  A Catalog of Felt Intensity Data for 570 Earthquakes in India from 1636 to 2009 , 2010 .

[11]  R. Bilham,et al.  A note on the Kangra M s = 7 . 8 earthquake of 4 April 1905 , 2022 .

[12]  Jérôme Lavé,et al.  Interseismic strain accumulation on the Himalayan crustal ramp (Nepal) , 1995 .

[13]  Paul Tapponnier,et al.  Kinematic model of active deformation in central Asia , 1993 .

[14]  P. Reimer,et al.  Extended 14C Data Base and Revised CALIB 3.0 14C Age Calibration Program , 1993, Radiocarbon: An International Journal of Cosmogenic Isotope Research.

[15]  P. Molnar,et al.  Rupture zones of great earthquakes in the Himalayan region , 1989 .

[16]  Monalisa,et al.  Geological setting of the 8 October 2005 Kashmir earthquake , 2009 .

[17]  V. Gaur,et al.  Surface deformation in the region of the 1905 Kangra Mw = 7.8 earthquake in the period 1846–2001 , 2005 .

[18]  R. Bilham,et al.  Apparent Himalayan slip deficit from the summation of seismic moments for Himalayan earthquakes, 1500-2000 , 2005 .

[19]  R. Bilham.  Earthquakes in India and the Himalaya: tectonics, geodesy and history , 2004 .

[20]  Caitlin E. Buck,et al.  Intcal04 Terrestrial Radiocarbon Age Calibration, 0–26 Cal Kyr BP , 2004, Radiocarbon.

[21]  Wenjin Zhao,et al.  Deep seismic reflection evidence for continental underthrusting beneath southern Tibet , 1993, Nature.

[22]  S. Wesnousky,et al.  Earthquake Recurrence and Rupture Dynamics of Himalayan Frontal Thrust, India , 2001, Science.

[23]  R. Briggs,et al.  Paleoseismic evidence of great surface rupture earthquakes along the Indian Himalaya , 2006 .

[24]  A. Gansser.  Geology of the Bhutan Himalaya , 1983 .

[25]  Bertrand Meyer,et al.  Oblique Stepwise Rise and Growth of the Tibet Plateau , 2001, Science.

[26]  R. Chander.  Southern limits of major earthquake ruptures along the Himalaya between longitudes 75° and 90°E , 1989 .

[27]  J. Achache,et al.  India–Eurasia collision chronology has implications for crustal shortening and driving mechanism of plates , 1984, Nature.

[28]  M. Stuiver,et al.  Discussion: Reporting of 14 C Data , 1977 .

[29]  S. Sapkota,et al.  Evidence for a Great Medieval Earthquake (~1100 A.D.) in the Central Himalayas, Nepal , 2005, Science.

[30]  Richard G. Gordon,et al.  Effect of recent revisions to the geomagnetic reversal time scale on estimates of current plate motions , 1994 .

[31]  Indepth Team.  Deep Seismic Reflection Evidence for Continental Underthrusting beneath Southern Tibet , 1996 .

[32]  Roger Bilham,et al.  LOCATION AND MAGNITUDE OF THE 1833 NEPAL EARTHQUAKE AND ITS RELATION TO THE RUPTURE ZONES OF CONTIGUOUS GREAT HIMALAYAN EARTHQUAKES , 1995 .

[33]  J. Freymueller,et al.  GPS measurements of present-day convergence across the Nepal Himalaya , 1997, Nature.

[34]  John Douglas,et al.  Magnitude calibration of north Indian earthquakes , 2004 .

[35]  T. Nakata,et al.  Active faults of the Himalaya of India and Nepal , 1989 .

[36]  M. Coward,et al.  Indian Plate motion and shape: constraints on the geometry of the Himalayan orogen , 1991 .

[37]  J. Malik,et al.  Active faults and related Late Quaternary deformation along the Northwestern Himalayan Frontal Zone, India , 2003 .

[38]  Roland Bürgmann,et al.  Convergence across the northwest Himalaya from GPS measurements , 2002 .

[39]  S. Wesnousky,et al.  Long recurrence interval of faulting beyond the 2005 Kashmir earthquake around the northwestern margin of the Indo-Asian collision zone , 2008 .

[40]  S. Acharyya,et al.  Regional geology and tectonic setting of northeast India and adjoining region , 1986 .

[41]  S. Wesnousky,et al.  Uplift and convergence along the Himalayan Frontal Thrust of India , 1999 .

[42]  Handong Tan,et al.  Partially Molten Middle Crust Beneath Southern Tibet: Synthesis of Project INDEPTH Results , 1996, Science.

[43]  W. Szeliga,et al.  Intensity, magnitude, location and attenuation in India for felt earthquakes since 1762 , 2010 .

[44]  D. Jackson,et al.  A note on early earthquakes in northern India and southern Tibet , 2003 .

[45]  Rhett Butler,et al.  Global seismographic network records the Great Sumatra‐Andaman earthquake , 2005 .