Magnitude calibration of north Indian earthquakes

N. N. Ambraseys, J. Douglas

Research output: Contribution to journalArticle

242 Citations (Scopus)

Abstract

This article is concerned primarily with the evaluation of the size and location of northern Indian and southern Tibetan earthquakes during the last 200 yr. It draws attention to the problems of assessing intensity of early and more recent earthquakes in a built environment, which is different from that for which the intensity scale has been constructed and to the way in which isoseismals are drawn. Through a re-evaluation of intensities and a reassessment of isoseismals, a formula for the estimation of surface wave magnitude using isoseismal radii is derived. This formula is used to estimate the surface wave magnitudes of 16 earthquakes that occurred in the region between 1803 and 1900. This study shows that it is possible to calculate accurate surface wave magnitudes for earthquakes that occurred before the advent of the scale and that there is no need to resort to empirical formulae for the assessment of the size and seismic moment release of pre-20th-century earthquakes. Also derived are formulae for the conversion of Ms to M0. In total, locations, surface wave magnitudes and M0 estimates are presented for 43 important events that occurred in the region between 1803 and 1974, eight of which were in the lower crust or were subcrustal. We find that the M0-Ms scaling for India yields smaller Ms than the global relation and that the methodology used can help to evaluate more realistic slip rates as well as to address other issues related to earthquake hazard in northern India.

LanguageEnglish
Pages165-206
Number of pages42
JournalGeophysical Journal International
Volume159
Issue number1
DOIs
Publication statusPublished - Oct 2004

Fingerprint

Earthquakes
earthquakes
surface wave
Calibration
calibration
earthquake
Surface waves
surface waves
India
slip rate
seismic moment
seismic hazard
evaluation
lower crust
estimates
hazards
crusts
Hazards
slip
methodology

Keywords

  • earthquakes
  • Himalayas
  • intensity
  • magnitude
  • north India

Cite this

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Magnitude calibration of north Indian earthquakes. / Ambraseys, N. N.; Douglas, J.

In: Geophysical Journal International, Vol. 159, No. 1, 10.2004, p. 165-206.

Research output: Contribution to journalArticle

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