Seismic moment release data in earthquake catalogue: Application of Hurst statistics in delineating temporal clustering and seismic vulnerability

Abstract

Sequential cumulative moment release data of macroearthquakes (Mw≥4.3) of seventeen seismic zones (A to Q) belonging to NE-Himalaya, Burmese-Andaman arc and West- Sunda arc are analysed by Hurst analysis, a non-parametric statistical procedure to identify clustering of low and high values in a time series. The moment release in a zone occurs in alternate positive, negative and positive sloping segments forming a wave like pattern with intervening small horizontal segment. The negative sloping segments indicate decelerated moment release pattern or temporal slackening of elastic strain release with high b–value (>0.95). The horizontal segment indicates temporal clustering of moderate magnitude events/seismic moments with moderate b-values (0.8–0.95). The positive segment is characterised by accelerated moment release within a short span of time indicating temporal clustering of larger magnitude earthquakes/seismic moments and exhibit lowest b–value (<0.7). All zones attest moderate to high Hurst K values, range 0.7-0.86. The pattern in Hurst plots, specially a reversal of trend after prolong negative slope is used for earthquake prognostication in the seismic zones. Our analysis shows that most of the zones register a notable reversal of Hurst clustering trend after a prolonged negative slope which is accompanied by a major earthquake near its end. However, South Burma region (Zone-I) and Tripura fold belt and Bangladesh Plain (Zone-K) do not show any moderate or large shock around the end of the negative sloping trend in Hurst plot. Hence, these two zones can be considered more prone to produce moderate to larger earthquakes in future.