Wednesday, September 30, 2009

Magnitude 6.6 South Sumatra Earthquake following September 30, West Sumatra earthquake

Magnitude 6.6 struck South Sumatra region on Thursday, October 01, 2009 at 08:52:29 AM local time. The epicenter located 270 km southeast of the damaging M 7.6 earthquake of September 30, 2009 offshore Padang at position 2.589°S, 101.546°E. It is not clear at present if these events are related but there is a big possibility that the Padang earthquake triggering the October 1st earthquake. Hundreds buildings collapse while fatalities are not reported yet but expected to rise.

According to USGS, the October 1st, 2009 Mw6.6 earthquake in southern Sumatra occurred as a result of shallow strike-slip faulting within the Sunda Plate. In the epicentral region of this earthquake, the Australian plate moves northwestwards with respect to the Sunda Plate at a rate of approximately 65 mm/yr. Oblique convergence at the trench, to the west of this earthquake, is partitioned between thrust motion on the subduction zone interface and strike-slip motion in the upper plate, near the Sumatra Fault. Todays earthquake is likely related to the latter strike-slip component of this motion, accommodating the northward motion of the Sunda block with respect to the interior of the Eurasian Plate. On the basis of the currently available fault mechanism information and a depth of 15 km, it is likely that this earthquake occurred along the Sumatran Fault or on a closely related structure. The recent earthquake is consistent with NW-directed, right-lateral displacement along the Sumatran Fault system.

Intensity Map

Magnitude 7.6 earthquake hits Padang, West Sumatra

A powerful earthquake rocked western Indonesia Wednesday, trapping thousands under collapsed buildings — including two hospitals — and triggering landslides. At least 75 people were killed; the death toll was expected to rise. (Update: The official release on October2, a total of 1100 people were confirmed dead and 421 seriously injured, these numbers are still expected to rise along with the search and rescue progress.)

The magnitude 7.6 quake struck at 5:15 p.m. local time (1015GMT, 6:15 a.m. EDT), just off the coast of Padang city at position 0.789°S, 99.961°E. A tsunami warning for countries along the Indian Ocean was issued, and panicked residents fled to higher ground fearing giant waves. The warning was lifted about an hour later.

Initial reports received by the government said 75 people were killed, but the real number is expected to rise shortly.

The quake triggered landslides that cut all roads to Padang. Power and telecommunications were also cut. Fire also broke out in buildings on a road to the city, officials said.

The intensity Map
Moment tensor solution
Population exposure

A man stands in front of a collapsed building after an earthquake hit Padang, on Indonesia's Sumatra island September 30, 2009 (Reuters)

Wednesday, September 2, 2009

A magnitude 7.0 Earthquake Strikes West Java

A magnitude of 7.0 earthquake killed at least 32 people and forced thousands to evacuate on Indonesia's main island of Java on Wednesday, September 02, 2009 at 02:55:01 PM local time. The death toll was expected to rise . Over 3,586 homes were damaged. The epicenter of the quake was 195km south of Jakarta and 95km south of Bandung city in the position of 7.778°S, 107.328°E with the uncertainty of horizontal +/- 6.6 km (4.1 miles); depth +/- 12.3 km (7.6 miles).

The 7.0 magnitude quake, as recorded by the U.S. Geological Survey, shook buildings in the capital Jakarta and flattened homes in villages closer to the epicenter in West Java. The quake was felt over roughly half of Java Island. In the capital, Jakarta, 120 miles (190 kilometers) from the epicenter, office workers ran onto the streets. A tsunami warning was issued after the quake struck, but revoked an hour later.

The worst report of fatalities was from a village in Cianjur district, where about 30 people were still believed trapped under rocks and dirt after a landslide triggered by the tremor buried their homes.

Update: on Thursday (September3, 2009 afternoon) the government report that the total casualties in the entire West Java Province reaches the number of 54, 147 peoples wounded and 10.000 evacuated. The construction damaged includes 34 homes totally destroyed, 11.000 heavily destroyed and light damage on 15.000 houses.