Sunday, February 22, 2009

About the website

This website was built in response to the limited sources of information available in English concerning natural disasters in Indonesia. It is meant to provide information understandable to the broad international community, especially those interested in disaster response.

The website hosted by an Indonesian geologist. The publisher wishes to thank the Visualization Center of San Diego State University for its contribution to this effort.

This website consists mainly of current information about disasters occurring in Indonesia, especially related to geological conditions. It also contains analyses of these events and information on important meetings, conferences and workshops on Indonesian disasters and natural hazards. There are also links to other sources of information and other publications related to these subjects.

Hopefully, this website can become a source of basic information for those interested in disaster response in Indonesia and for those interested in conducting research in these topics. Hopefully it will prove of value to Indonesian disaster recovery.

Sunday, February 15, 2009

Sangihe-Talaud 7.2 Mw Earthquake, February 12, 2009

A moment magnitude 7.2 Mw was happen in Kepulauan Talaud, Indonesia on February 12, 2009, local time 01.34, resulting 2 fatalities, 10 heavy injured while other 42 people wounded and over 700 building collapse. More than 5000 citizen were evacuated to avoid the affect of continuous aftershock in magnitude 4 Mw to 6 Mw that are still happening in the region.

This earthquake likely occurred as a result of reverse faulting on or near the plate-boundary system separating the Philippine Sea and Celebes Sea basins. Northeastern Indonesia is characterized by complex tectonics in which motions of numerous small plates are accommodating large-scale convergence between the Philippine Sea and Sunda plates. In the region of today's earthquake, the Philippine Sea plate moves west-northwest with respect to the Sunda plate at a velocity of about 62 mm/year. Locally, arc-arc collision is occurring between the Sangihe and Halmahera micro plates, wedging between them the Molucca Sea micro plate, which subducts beneath both (i.e. to the east and west) and forms an inverted-U-shaped seismic zone. Seismicity within the Molucca Sea plate is active to depths of approximately 260 km to the east and 400 km to the west. The tectonic setting of this region is unique in that it is the only global example of an active arc-arc collision consuming an oceanic basin via subduction in two directions and it drive the area to become one of the most tectonic-active in the world today.

The earthquake occurred approximately 30 km off the western coast of the Pulau Salebabu (Indonesia) in an area that has seen large earthquakes in the past. Since 1986, there have been two earthquakes with magnitude greater than 7 in this region.

USGS data showed that the epicenter located in 3.902 deg N, 126.400 deg E with depth 20 km with magnitude 7.2 Mw. Global CMT Moment Tensor Solution shows that this earthquake caused by thrust faulting with direction of 181 deg NE and dip 37 deg. This earthquake supposed to be potentially trigger tsunami, but it was reported that no tsunami occurred.

The earthquake summary poster from USGS

Monday, February 2, 2009

Heavy floods and landslides in Indonesia over the week

Heavy rains over the past weeks have caused floods and landslides in various parts of Indonesia, causing heavy economic losses.


Floodwaters engulfed several villages in Kroya district, Cilacap regency-Central Java, destroying 450 hectares of almost-harvested rice crops. While in East Java floods due to the overflowing of the Bengawan Solo River has submerged 1,730 hectares of rice fields in 61 villages in Bojonegoro district. The area of flooded rice fields might widen in the days ahead as the river was continuing to overflow. In Surakarta-Central Java, 500 residents in Joyotakan got ready to flee their homes as the nearby Bengawan Solo River burst its banks and flooded some homes with water as high as 1.5 meters. Surakarta city remained on high alert after water engulfed most of the city. Besides flooding, the heavy rains also triggered landslides in several regencies.

In Madiun-East Java landslide happened in Kepel village on Friday, 30 January 2009 destroyed one house and killed one person. The landslide occur at the hill slope of the Wilis Mountain region, the area consists of andesitic breccias bedrock, weathered into soil in silt-clay size, medium plasticity with 2-5 m thickness. The landslide triggered by the morphology, lithology and bad drainage condition during the heavy rain prior to the landslide.

While in Karanganyar-Central Java, on Friday, 30 January 2009 landslide hit Nglegok village and killed 6 people. The landslide occurs at the hill slope of the Lawu Mt region which consists of tufa andesitic breccias bedrock, weathered into soil in sand-silt-clay size. The landslide triggered by the morphology, lithology and the heavy rain several days prior to the landslide.
In Kebumen and Sruweng-Central Java, on Friday, 30 January 2009 landslide hit Penusupan village and destroyed 6 houses.

In Banyumas-Central Java, landslides destroyed at least 15 homes on Sunday February 1, 2009 in the villages of Cihonje, Telaga and Paningkaban, in Gumelar district.


Several districts and cities in South Sulawesi Province were hit by floods, submerging residential areas, farm land, fish ponds, and cacao plantations

In Malino, Gowa District, a landslide killed one person and in Takalar District a flood claimed another life on Sunday, February 1, 2009 while in North Luwu, a number of houses and hundreds of hectares of cacao plantations were flooded. Some 200 families were forced to flee to higher ground in Makassar due to the flood. Meanwhile, floods have inundated at least 100 houses and hectares of paddy fields in Gowa since 26 January 2009. In Malo sub district of the province, some 250 families were forced to evacuate to safer areas due to the floodwaters reaching a height of more than one meter in their residential areas.

Sources : Metro TV, Kompas, Geological Agency of Republic of Indonesia

Landslide Prone Area, February 2009

Landslide prone area during the rainy season of 2009, in all provinces of Indonesia. Presented both as maps and tables by the Indonesian Government. You can find it in here.

Eruption of Mt. Dieng, Central Java, 15 January 2009

On Thursday 15th January 2009 Dieng Volcano was raised from level I (normal) to a level II alert (out of a maximum of IV) after two phreatic eruptions on 15th January. The eruptions occurred at Sibanteng Crater at 8:00 and 8:30 am. Volcanic material was ejected 50 m from the crater causing no fatalities since it is located away from the settled area. It was reported that there was no poisonous gas detected in the area. The phreatic eruption was initiated when the Sibanteng Crater collapsed causing blockage of the crater and a build-up of gas pressure. The material flowed down, blocking the Suci River threatening to flood the populated area below. It is reported that on 22 January the Suci River was still flowing but that the 40.000 m3 of material in the Sibanteng Crater present a threat to the villages of Pulosari, Ngandam and Tempuran in the event of heavy rain.

Dieng Volcano complex is located near Wonosobo, Central Java, Indonesia. For several centuries volcanic activity at Dieng has been dominated by phreatic eruptions, and geothermal activity (fumaroles, solfataras, mud pools, hot springs). The volcano is composed of two strato volcanoes (Butak Petarangan and Dieng) and many craters. Warm acidic lakes fill some of the craters. Volcanic cones at Dieng include the following - Bismo, Srojo, Binem, Pangonan, Merdodo, Pagerkandang, Nogosari, Petarangan, Telogo Dringo, Pakuwaja,Kendil, Kunir and Prambanan.

Dieng Volcano is noted for the release of carbon dioxide, which sometimes results in fatalities to residents as it happened on 20 February 1979 when 149 died after inhaling poisonous gas from the eruption of its Timbang Crater. Fumarole areas include Kawah (crater) Sikidang, Kawah Sigajah, Kawah Kumbang, Kawah Sibanteng, Kawah Upas,Telogo Terus, Kawah Pagerkandang, Kawah Sipandu, Kawah Siglagah and Kawah Sileri. Butak Petarangan is the second highest volcano located in the Dieng complex. It consists of a crater-lake named Telogo Dringo and Condrodimuko Fumarole Field. Sileri Crater which is the most active had its last phreatic eruption in July 2003.

The morphology of the area is mostly hilly, with gradients in the range of 10-40 degrees. It lies 1900-2000 meters above sea level. The lithology mostly consists of piroclastic deposits. The plastic soil is reddish brown in color and the grain size of the soil is silt-clay with thicknesses between 1-3 meters. The Sibanteng Crater landslide was triggered by the lithology, morphology and the water condition of the area. Heavy rain occurred during 3 days prior to the landslide. Based on observation, the poisonous gas concentration is still below the allowed limits.

Based on visual and data analysis, on Thursday 22th January 2009 at 4:00 pm, Dieng Volcano's status decreased from level II to level I (Normal). Howevere there is still potential for phreatic eruptions, and general awareness must take this into account, especially during heavy rains which could trigger more landslides.

Resource : Report from Geology Agency, Republic of Indonesia

Kawah Sibanteng before eruption (source image : Virtual Tourist)