Global regression relations for conversion of surface wave and body wave magnitudes to moment magnitude

Abstract

A homogenous earthquake catalog is a basic input for seismic hazard estimation, and other seismicity studies. The preparation of a homogenous earthquake catalog for a seismic region needs regressed relations for conversion of different magnitudes types, e.g. m b , M s , to the unified moment magnitude M w. In case of small data sets for any seismic region, it is not possible to have reliable region specific conversion relations and alternatively appropriate global regression relations for the required magnitude ranges and focal depths can be utilized. In this study, we collected global events magnitude data from ISC, NEIC and GCMT databases for the period 1976 to May, 2007. Data for m b magnitudes for 3,48,423 events for ISC and 2,38,525 events for NEIC, M s magnitudes for 81,974 events from ISC and 16,019 events for NEIC along with 27,229 M w events data from GCMT has been considered. An epicentral plot for M w events considered in this study is also shown. M s determinations by ISC and NEIC, have been verified to be equivalent. Orthogonal Standard Regression (OSR) relations have been obtained between M s and M w for focal depths (h \ 70 km) in the magnitude ranges 3.0 B M s B 6.1 and 6.2 B M s B 8.4, and for focal depths 70 km B h B 643 km in the magnitude range 3.3 B M s B 7.2. Standard and Inverted Standard Regression plots are also shown along with OSR to ascertain the validation of orthogonal regression for M s magnitudes. The OSR relations have smaller uncertainty compared to SR and ISR relations for M s conversions. ISR relations between m b and M w have been obtained for magnitude ranges 2.9 B m b B 6.5, for ISC events and 3.8 B m b B 6.5 for NEIC events. The regression relations derived in this study based on global data are useful empirical relations to develop homogenous earthquake catalogs in

Multi-parameter algorithm for Earthquake Early Warning

“…These parameters are then used for estimating the magnitude of the earthquake. The estimated magnitude is found to be in good agreement with the catalogue magnitude with a minimum uncertainty which is due to the inherent error in M w estimation (Das et al 2011;Das 2013).…”

Homogenization of Earthquake Catalog for Northeast India and Adjoining Region

“…OSR relation for conversion of surface and body wave magnitudes to moment magnitudes requires the value of the error variance ratio g. For the events data considered in this study, we use the standard deviations 0.15, 0.20 and 0.25 for M w, M s and m b , respectively as considered by THINGBAIJAM et al (2008). Software developed by the authors in another study (DAS et al, 2011) has been used to derive the regression relations.…”

“…With respect to m b determinations by ISC and NEIC, it is observed in several studies that the two determinations are not equivalent (NATH and THING-BAIJAM, 2010;DAS et al, 2011). For the conversion of m b , ISC to M w,GCMT in the magnitude range 4.7 B magnitude B 6.6, and m b,NEIC to M w,GCMT in the magnitude range 4.6 B magnitude B 6.8, we follow the same approach using data sets of 171 and 149 events, respectively, for the period 1964-2006.…”

The new empirical magnitude conversion relations using an improved earthquake catalogue for Turkey and its near vicinity (1900–2012)

“…These empirical conversion relations provide homogeneity of the earthquake catalogue in terms of unified scale. For instance, different conversion relationships have been developed on a regional scale with different methods by Richter (1956a, 1956b), Kanamori (1983), Ambraseys (1990), Papescu et al (2003), Ulusay et al (2004), Deniz (2006), Scordilis (2006), Kalafat et al (2007), Grünthal (2009), Akkar et al (2010), Das (2011Das ( ), Çıvgın (2015, and Bayrak et al (2005Bayrak et al ( , 2009). On the other hand, various regression analyses have been performed for local scale by using different methods and databases.…”