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A series of powerful earthquakes strikes North of Sumatra |
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Click here for latest Information: Earthquake of magnitude Mb=8.9 (M9.0 on Richter scale, USGS report) has hit the Sumatra region of Northern Indonesia early morning 6.28 AM (IST) of 26th of Dec., 2004. The approx. location of earthquake was 3.30ºN lat and 95.78ºE. The earthquake has shaken large area around the Sumatra Island of Indonesia and Andaman and Nicobar islands of India and huge sea waves have affected the coastal regions of other neighboring countries. The sea waves generated from the sea floor are termed as 'Tsunami' which has created devastation in the coastal regions. The approx. location of hypocenter of main shock was around 10 km underneath the sea floor indicating shallow earthquake. More than seven large aftershocks have been recorded after the main shock at National Earthquake Information Center of United States of Geological Survey, USA. More details about the location characteristics of these earthquakes can be viewed at- (http://wwwneic.cr.usgs.gov/neis/bulletin/bulletin.html) The preliminary location of epicenter and the time
of arrival of earthquake is briefly mentioned in following table indicating
severity of rupture mechanism (in terms of seismogenesis) in the region:
(Source: NEIC USGS, USA)
(* indicate earthquakes near Andaman and Nicobar Island of India) The earthquake has generated tremendous sea waves called 'Tsunami' which has traveled towards coastal regions of Eastern Sri Lanka, Northern Indonesia and South east coast of India which includes Coastal Andhra Pradesh, Tamil Nadu and West Bengal. Large portion of southeast India especially coastal region has experienced shaking and hundreds of fisherman are missing as per the preliminary information received from local authorities and media. Due to the low tide hours, thousands of fisherman have been caught under Tsunami waves in early morning hours. More than 4500 people have lost their lives in Sri Lanka, about 500 people in coastal Andhra Pradesh of southern India and abour 2500 number are feared dead in Tamil Nadu as well. This is worst known tragedy in recent time due to Tsunami effect in India. The seismic activity in Andaman and Nicobar Island have been known to be prominent since the last major earthquake which hit in 1941 measuring 7.7 on moment magnitude. The earthquake has caused widespread damage along with large Tsunami waves in the Bay of Bengal. The northern Sumatra have been experiencing large earthquake since past but the current main shock was among the largest known earthquakes during last few decades. It is important to note that all of these earthquakes as shown in above table are of very large size indicating huge amount of strain energy release in the region indicating large rupture zone with most of aftershock in the northern area of main shock. The main shock of 9.0 was followed by more than seven large shocks and it is expected that the aftershock sequence may continue for next few months. Generally each aftershock is expected to of size less than 1 or 2 magnitude units than its main shock. Each unit of increase in magnitude indicates 10 times larger amplitude of peak of recorded wave and approximately 30 times higher energy release. Thus earthquake of magnitude 7.0 will have 10 times higher maximum amplitude and 30 times higher energy release as compared to magnitude 6.0 earthquake. |
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