The 26 January 2001 M 7.6 Bhuj, India, Earthquake: Observed and Predicted Ground Motions

Although local and regional instrumental recordings of the devastating 26, January 2001, Bhuj earthquake are sparse, the distribution of macroseismic effects can provide important constraints on the mainshock ground motions. We compiled available news accounts describing damage and other effects and interpreted them to obtain modified Mercalli intensities (MMIs) at >200 locations throughout the Indian subcontinent. These values are then used to map the intensity distribution throughout the subcontinent using a simple mathematical interpolation method. Although preliminary, the maps reveal several interesting features. Within the Kachchh region, the most heavily damaged villages are concentrated toward the western edge of the inferred fault, consistent with western directivity. Significant sediment-induced amplification is also suggested at a number of locations around the Gulf of Kachchh to the south of the epicenter. Away from the Kachchh region, intensities were clearly amplified significantly in areas that are along rivers, within deltas, or on coastal alluvium, such as mudflats and salt pans. In addition, we use fault-rupture parameters inferred from teleseismic data to predict shaking intensity at distances of 0–1000 km. We then convert the predicted hard-rock ground-motion parameters to MMI by using a relationship (derived from Internet-based intensity surveys) that assigns MMI based on the average effects in a region. The predicted MMIs are typically lower by 1–3 units than those estimated from news accounts, although they do predict near-field ground motions of approximately 80%g and potentially damaging ground motions on hard-rock sites to distances of approximately 300 km. For the most part, this discrepancy is consistent with the expected effect of sediment response, but it could also reflect other factors, such as unusually high building vulnerability in the Bhuj region and a tendency for media accounts to focus on the most dramatic damage, rather than the average effects. The discrepancy may also be partly attributable to the inadequacy of the empirical relationship between MMI and peak ground acceleration (PGA), when applied to India. The MMI–PGA relationship was developed using data from California earthquakes, which might have a systematically different stress drop and therefore, a different frequency content than intraplate events. When a relationship between response spectra and MMI is used, we obtain larger predicted MMI values, in better agreement with the observations.

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

[2]  A. Johnston.  Seismic moment assessment of earthquakes in stable continental regions—III. New Madrid 1811–1812, Charleston 1886 and Lisbon 1755 , 1996 .

[3]  R. Bilham.  Slip parameters for the Rann of Kachchh, India, 16 June 1819, earthquake, quantified from contemporary accounts , 1999, Geological Society, London, Special Publications.

[4]  Thomas H. Heaton,et al.  Relationships between Peak Ground Acceleration, Peak Ground Velocity, and Modified Mercalli Intensity in California , 1999 .

[5]  Thomas C. Hanks,et al.  Common features of the excitation and propagation of strong ground motion for North American earthquakes , 1992 .

[6]  T B Comstock,et al.  U. S. Geological Survey , 1907, Radiocarbon.

[7]  B. Kennett,et al.  Lg-wave propagation in heterogeneous media , 1989 .

[8]  P. Bodin,et al.  Source Characteristics of Aftershocks of the India Republic Day Earthquake , 2001 .

[9]  G. Atkinson,et al.  Source Parameters of Earthquakes in Eastern and Western North America Based on Finite-Fault Modeling , 2002 .

[10]  R. Musson,et al.  The Barrow-in-Furness Earthquake of 15 February 1865: Liquefaction from a Very Small Magnitude Event , 1998 .

[11]  P. Molnar,et al.  Focal depths of intracontinental and intraplate earthquakes and their implications for the thermal and mechanical properties of the lithosphere , 1983 .

[12]  Arch C. Johnston,et al.  Seismic moment assessment of earthquakes in stable continental regions—II. Historical seismicity , 1996 .

[13]  David M. Boore,et al.  Regional Lg attenuation for the continental United States , 1997, Bulletin of the Seismological Society of America.

[14]  S. Hough,et al.  On the modified Mercalli intensities and magnitudes of the 1811/1812 New Madrid, central United States, earthquakes , 1999 .

[15]  Arch C. Johnston,et al.  Earthquakes in stable continental crust , 1990 .

[16]  Linking Historical Intensity Observations with Ground-motion Relations for Eastern North America , 2001 .

[17]  Walter H. F. Smith,et al.  Free software helps map and display data , 1991 .

[18]  Vinod K. Gaur,et al.  Geodetic contributions to the study of seismotectonics in India , 2000 .

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

[20]  Gail M. Atkinson,et al.  Generic finite-fault model for ground-motion prediction in eastern North America , 1999, Bulletin of the Seismological Society of America.

[21]  C. W. Stover,et al.  Seismicity of the United States, 1568-1989 (revised) , 1993 .

[22]  Jose Pujol,et al.  Three-Dimensional Geometry of the Reelfoot Blind Thrust: Implications for Moment Release and Earthquake Magnitude in the New Madrid Seismic Zone , 2001 .

[23]  Kusala Rajendran,et al.  Characteristics of Deformation and Past Seismicity Associated with the 1819 Kutch Earthquake, Northwestern India , 2001 .

[24]  Gail M. Atkinson,et al.  Empirical Relationships between Modified Mercalli Intensity and Response Spectra , 2000 .

[25]  E. Fielding,et al.  The January 26, 2001 Bhuj, India Earthquake , 2001 .

[26]  Hilla Peretz,et al.  Ju n 20 03 Schrödinger ’ s Cat : The rules of engagement , 2003 .

[27]  Gail M. Atkinson,et al.  The shape of ground motion attenuation curves in southeastern Canada , 1992, Bulletin of the Seismological Society of America.

[28]  Gail M. Atkinson,et al.  The Damage Potential of Eastern North American Earthquakes , 1993 .

[29]  Mario Ordaz,et al.  A spectral analysis of the 21 May 1997, Jabalpur, India, earthquake (Mw = 5.8) and estimation of ground motion from future earthquakes in the Indian shield region , 1999, Bulletin of the Seismological Society of America.