Earthquake catalogue of South Asia in a homogenous magnitude framework

 
 

 

Some keynotes and the data

 

 

Downloads: Right click on the link and select 'save as'.

Earthquake catalogue

 

Early instrumental  and instrumental (1900-2008) [.txt format, 3.6 MB]

Pre-instrumental (Prior to 1900) [.txt format, 18.0 KB]

readme file [.pdf format, 20.0 KB]

 

 
 

Several deadly earthquakes have occurred in South Asia causing huge devastations; 2001 Bhuj MW,  2004 Sumatra MW 9.1, and 2005 Kashmir MW 7.6 in the recent memory. The earthquakes occurring in the region accounts for roughly 28.6% of the global earthquake fatalities during the last century. A homogenous and consistent earthquake catalogue is an imperative data for seismic hazard studies in the region. We, therefore, undertake the task of compiling a one, addressing the following:

  • Existing data sources,

  • Errors associated with the magnitude types,

  • Relationships between the different magnitude types, and

  • Quality of the compiled catalogue

     
Figure: A seismicity map of South Asia depicting the main shock events covering a period: 1900-2008AD.
 

 

The compiled records of earthquake occurrences cover a period: 0162-2008; several publications are consulted as listed in the readme file.

 

We note the following major observations:

  • Reportings of earthquake magnitudes by major agencies in MS and MW are reasonably consistent, while those given in mb show minor systematic variations to the tune of 0.08-0.1 units.

  • mb is lower than MW by 0.16 units while ML is lower than MW by 0.6-0.8 units depending on the magnitude.

  • Application of a declustering algorithm  indicates that the aftershock sequences of major earthquakes prior to 2008 terminate, except those for 2004 Sumatra MW 9.1 and 2005 Kashmir MW 7.6 earthquakes, which appears to extend till the end of the catalogue.

  • Average magnitude uncertainties of instrumental records (1964-2008) is seen to be nearly 0.4 while that of pre- and early instrumental  records (i.e. prior to 1900, and 1900-1963) could come to approximately 0.7 and 0.5 units, respectively.

  • The temporal variations of the data completeness for the time-period 1900-2008 is evaluated on the basis of stable number of events for the magnitude range, which indicate three verges: first one spanning the entire period, the second one from 1964 onwards and the third one, considerable improvement in the reportings during the last two decades.

Caveat on the pre-instrumental records:
Historical earthquake reportings has several shortcomings:

  • Possibility of inhomogeneity cannot be ruled out in case of the historical earthquakes owing to non-calibrations due to lack of common reportings across the different studies.

  • The data is deemed to be highly incomplete and posses high uncertainties.

  • Appropriate treatment on the associated uncertainties and incompleteness is required.