Post On : July 25, 2015
RELATIVE PLATE MOTIONS
Indonesian archipelago is located in the convergence zone of four major tectonic plates: Eurasian plate, Indian-Australian plate, Pacific plate and Philippine plate. Interaction of these plates affected the seismo-tectonic of the Indonesian region.
The Indian-Australian plate moving northwards relative to Eurasian plate and the Pacific plate moving westward relative to both Indian-Australian and Eurasian plate.
Moreover, as a result of the India and Australia plates converging with and subducting beneath the Sunda plate at a rate of approximately 50 to 70 mm/yr.
DISCUSSION
The island of Java, within the Indonesian archipelago, sits atop the Eurasian plate. Movement of the Indian Ocean-Australian Oceanic plate under the Eurasian Plate is around 9 cm / year with a direction close to perpendicular towards the southern part of the Java Trench.
The Ciamis Earthquake of July 24, with magnitude 5.5 Mw occurred at a depth of about 82 km. The epicenter was reported to be 60 km away from the Southern Coast of Central Java. The earthquake did not generate a tsunamis though epicenter of earthquake was centered in the open ocean, because the energy released is not strong enough to trigger a tsunamis.
Earthquake shocks felt widely on South of Central Java. In the south of Ciamis Regency quake reaches about VI ? V MMI; Banjar and Cilacap about III ? IV MMI, and from analysis of Shake Map generated by MAIPARK Cat Model, that shown the building loss are quite low.
Based on MAIPARK research on variations of b-value (tectonic) character in the South of Central Java, we found that a ?Seismic Gap? has been identified in the South Coast of Central Java )represent by low b-values areas). This ?Seismic Gap? is a region with a potential for the occurrence of big earthquakes in the near future for the surrounding regions, such as the south coast Central and East Java. Research and government institutions should pay special attention to this region. The government?s disaster management institution should take necessary steps, towards a real effective mitigation program.
EXPOSURE AND LOSS
Maipark Cat-model has estimated no losses or very minor losses from this event.
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