Mentawai Earthquake Earthquake in October 2010 at the edge of the field of earthquake 2007 By Dr. Irwan Meilano
Mentawai earthquake in 2010 has claimed more than 100 deaths and material losses that many around the islands Pagai. USGS estimate the magnitude earthquake that occurred on Monday, October 25, 2010 at 21:42:22 in the amount of 7.7 Mw, ie calculation of Harvard CMT Mw 7.8, Universita Nagoya Japan estimates 7.7 Mw while BMKG namely M 7.2 ,
Some questions that can be asked of this earthquake-related, namely:
1. How large is the field of earthquakes and how strong the energy expended?
Based on the Mentawai earthquake for an area 2010 of 180km x 75 km with a maximum magnitude of the shift in the field of earthquake that is 1.3m. This shift dominant vertical directed. Shifting the vertical direction, and location very close to the sea trench (trench) can generate a tsunami. From some reports note high tsunami that reached 3 m in Pagai. The moment the quake generated that 0,65x10e21 NM.
The duration of this earthquake on the field of seismic sources ie longer than 50 seconds.
2. What is the link between the 2010 earthquake in Mentawai earthquake 2007
Mentawai earthquake of 2010 occurred on the outside toward the trench (trench) on the earthquake zone 2007. So 2010 earthquake slip to fill the void that has not been torn as a result of the earthquake of 2007. Energy accumulated at the end of this (figure 1) is generated as a result of shifting koseismik earthquake 2007 and postseismik major deformation.
Based on our previous studies it is known that the moment of the earthquake in 2007 which amounted 7,1x10e21 NM or Mentawai earthquake in 2007 had a strength 11 times greater than Mentawai earthquake of 2010.
The red color in Figure 1 below shows the areas of the tear (rupture) of the Mentawai earthquake of 2007. Color Blue indicates areas that have not torn by the earthquake of 2007. Picture focal mechanisms (beach ball) showing the location of the focus of the 2010 earthquake are in blue (which is not torn) from the 2010 earthquake.
3. Why 2010 earthquake resulted in a tsunami higher than the earthquake of 2007?
In 2007 the Mentawai earthquake maximum shift in the field of earthquake that is 5m in the vertical direction field. This large shifts are at a depth of 30 km which is just below the island of South Pagai. And few shifts close to the trench (trench) so that the volume of water that effectively lifted not a lot.
This differs from the Mentawai earthquake of 2007. Although the shift (slip) in the field of earthquake only 1.3m but this shift is very close to the trench. The shift will result in deformation near vertical trench on the seabed is very large so that the volume of water which is taken as well as more and generate a tsunami.
Shifts are close to the trough (trench) in which the rigidity of the lower rocks and velocity tear (rupture velocity) slower than the earthquake in general is often referred to as the tsunami earthquake, to distinguish it tsunamigenic earthquake.
4. Is it possible that an earthquake with a magnitude greater?
The earthquake on the main segment of the feared happened actually is in the northern part of the island Siburu or started from the South Siberut island until around Pulau Telo around the South Island of Nias. Long a source of major earthquake that is feared to occur is along approximately 300km. With magnitude earthquake that may occur is greater than Mw8.5.
Field Mentawai earthquake in 2007 (red color contour) and the main quake Mentawai 2010 (focal mechanism), aftershocks (red circle)
So that there is still potential large earthquake on the West Coast of Sumatra. Figure 2 above illustrates some of the aftershocks of the 2010 Mentawai earthquake with a magnitude greater than 5.5 Mw. From these images are shown that the area of the 2010 earthquake only occurs at the edges of the earthquake in 2007, and has not touched the main segments that we wait.
Source: http://www.fitb.itb.ac.id/great
No Comments