Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/7554
Title: SEISMICITY PRECURSORS ASSOCIATED WITH EARTHQUAKES IN THE CARHWAL HIMALAYA
Authors: R., Surya Prakash
Keywords: EARTHQUAKE ENGINEERING;SEISMICITY PRECURSORS;EARTHQUAKES;CARHWAL HIMALAYA
Issue Date: 2010
Abstract: Four types of seismicity precursors namely Vp/Vs ratio, b-value, foreshock activity and anomalous seismicity have been studied preceding three moderate and two small earthquakes that have occurred in the Garhwal Himalaya from 1996 to 2009. The epicenters of three earthquakes fall in the Lesser Himalaya and two in the Higher Himalaya. The seismological data collected from the telemetry network deployed in the environs of Tehri dam in the Garhwal Lesser Himalaya has been analysed and interpreted to study these seismicity precursors. Temporal variation of Vp/Vs ratio preceding at least three out five earthquakes exhibits a consistent pattern marked by first decrease followed by some recovery, again decrease and then recovery in the Vp/Vs ratio before the occurrence of mainshocks. The first stage of recovery in the Vp/Vs ratio is attributed to the occurrence of precursory seismic activity which is either characterised earthquake swarms or clusters of events occurring in the focal region before the mainshocks. The b-value decreased before the occurrence of three earthquakes and recovered after the mainshocks. All the five earthquakes are preceded by foreshock activity which is characterised by the occurrence of a single event (direct foreshock), in the form of clusters of 3 to 4 events, or their combination. Three earthquakes were preceded by the combination of both single foreshock and precursory foreshock swarms of 3 to 4 events within 30 days before the occurrence of mainshock. Onset of some anomalous seismicity which is either characterised by precursory swarms or clusters of 3 to 4 events has occurred before the moderate and small earthquakes. The precursor time for the swarm activity seems to be about 4 months for moderate earthquakes. This study has demonstrated that small and moderate earthquakes in the Garhwal Himalaya are characterised by the occurrence of seismicity precursors.
URI: http://hdl.handle.net/123456789/7554
Other Identifiers: M.Tech
Research Supervisor/ Guide: Gupta, S. C.
Kumar, Akhilsh
metadata.dc.type: M.Tech Dessertation
Appears in Collections:MASTERS' THESES (Earthquake Engg)

Files in This Item:
File Description SizeFormat 
EQD G20284.pdf3.41 MBAdobe PDFView/Open


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.