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| Titel |
Precursory Swarm Identification and Long-term Earthquake Prediction in Western Nepal Himalaya & its adjoining Indian Region |
| VerfasserIn |
D. Shanker, Harihar Paudyal, H. N. Singh |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024974
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| Zusammenfassung |
| Anomalous seismicity is first to take place as compared to other precursory phenomena due
to formation of various ruptures where considerable strain energy are accumulated, hence it
may be an important parameter for the prediction of long-range earthquake related hazards in
a region. Anomalous seismic activity associated with major earthquakes in the Western Nepal
Himalaya and its adjoining Indian region have been studied in an area bounded by
28.0o-31.0o N and 79.5o-82.2o E, using seismicity data from 1963-2006. In the present study,
anomalous/precursory swarm seismicity and the delineation of preparation zones
(
sim1.1 x 104 km2) are carried out for the future earthquake hazard using the temporal and
the spatial distribution of events considering the total events and the events with
mb
ge 4.3 in four anomalous episodes: Normal/ background (N); Anomalous/ swarm (A);
Precursory gap (G) and Mainshock sequence (M), respectively. Five cases of anomalous
seismicity have been identified: prior to three earthquakes that have already occurred and two
cases for which quiescence episodes still continues. Three medium size earthquakes of 1980
(mb 6.1), 1984 (mb 5.6) and 1999 (mb 6.6) occurred in the Western Nepal and its adjoining
Indian region were preceded by well defined patterns of anomalous seismicity/
precursory swarm. The first of these was the Bajhang earthquake of which most of its
preparatory processes during 1967-1980 were confined approximately in the central
part of the area between the MCT and the MBT. Subsequently, the seismic activity
shifted towards east in the northeast-southwest direction which produced another
mainshock of 1984 (mb5.6). Seismic activity started concentrating in and around
Chamoli area (India) since 27 November 1995 which was preceded by a quiet low
seismicity in the region. After Chamoli earthquake in 1999, a low seismic activity
was observed in the region which continued for the next two years till 14 April
2001. The seismic activity again shifted towards southeast and started concentrating
in the region east-northeast of Bajhang earthquake, since April 2001, in which
anomalous pattern in seismicity is observed on two occasions. On analyzing the
seismicity data from 1999 to 2006, two additional cases of characteristic seismicity
patterns were observed: (1) 1999-2006, and (2) 2003-2006. In these two cases, though
the anomalous seismicity exists, no mainshock has occurred so far. After critical
analysis of the data, it is observed that the seismicity from 1999 onwards fluctuates
in the order as low-high-low phases. The analyses suggest that a shallow focus
(h
le30 km) earthquake of about M 6.5 and more may occur at any time in the delineated
preparatory area (29.4o-30.6o N and 81.3o-81.8o E) in its southern part till 2011.
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