Peta Gempa Indonesia - A thick red line that seemed to divide into two parts of Sumatra island from north to south. The red line indicates Semangko slip faults or fault, the cause of the earthquake in Sumatra Island and mainland, which extends from Aceh to Lampung Bay Watermelon. Red color is what distinguishes the map of earthquake seismic zoning map in 2002 with Indonesia in 2010, the newly launched Ministry of Public Works (PU) in Jakarta, last Friday.
Peta Gempa - Not only in Sumatra, a fairly prominent red spots were also seen on the island of Sulawesi and Papua. Small islands in East Nusa Tenggara, Maluku and North Maluku not spared from the red spots. "The fundamental difference with SNI 03-1726-2002 is the old map was not entered several active fault on the mainland," said Irwan Meilano, geodesy experts from the Bandung Institute of Technology, involved in the Indonesian earthquake map revision team in 2010. "Differences of color from red to red once it was because there was fault contribution from the mainland. It had not been included in the old map, now a little bit there."
In the new seismic zoning map, the Ministry of Public Works include the acceleration of soil above the bedrock during the earthquake. In the seismic zoning map, each island was given a variety of colors: from light blue to dark red. "The older or more colors to the right, (that) the higher the danger level," said M. Ridwan, geologists from the Center for Housing Research and Development, Ministry of Public Works.
This new map, said Ridwan, a revision of the map in 2002, which is considered too long. "She's been eight years, and during that period many large earthquakes in Indonesia, so a lot of pressure to immediately replace it," he said.
To make this new map, the Ministry of Public Works formed in 2010 earthquake map revision team, which consists of experts in geology, seismology, and geodesy. Merger experts was conducted to determine all sources of earthquakes that may occur, start an earthquake in the subduction zone (meeting of two tectonic plates) to the most difficult to find the source of the earthquake in the mainland, namely the active fault, "said Irwan." Earthquake Yogyakarta, for example, It happened at Fault Opak.
Looking for an active fault is not actually the case is difficult, because the satellite data could show a clear fault line morphology. But not all the faults that have the same potential for disaster, so the team should revise the quantification of how active faults do it before the stain it with red to dark red color. "Looking for an active fault but there has never been a big earthquake in the fault record is very difficult," said Irwan. "If we enter a similar fault entirely, red yes all, no place to live, except in Borneo."
To overcome that problem, each expert in a team of 11 people are doing some approximation method. Geological experts approached by determining whether a potential earthquake source fault through morphological and geological. Seismology experts observe how large the earthquake potential of the corner kegempaannya. Meanwhile, geodesy experts determine that the speed of shear rate by measuring the parameters of fault slip rate. "Once there was a definition of seismic source is established, we can calculate the mathematical relationship between the length and magnitude of the earthquake magnitude earthquake," he said.
Geodetic observations needed to measure how active a fault. Observations that indicate faults in Java, for example, Lembang, only one-tenth the level of activity in the Sumatra fault. "The rate of shear is not as fast as in the Sumatra fault," he said. "Sumatra Fault shear rate in the teens up to 20 millimeters per year, but if the Lembang Fault only two millimeters per year."
When compared with the old map that measures the potential for disaster (hazard) of average seismicity in one place, this new map in greater detail by considering the morphology, seismic faults, and fault activity level. "It follows the standard methodology followed in the big countries, like Japan and the United States," said Irwan. "The model also has three dimensions, so a lot of improvement than the map in 2002."
Head of Research and Development Ministry of Public Works Sumaryanto Widayatin stated that this new map has been aligned with the International Building Code 2006 as well as three-dimensional analysis of seismic sources with a period of 475 and 2475 years for the peak ground acceleration, response spectra of short period (0.2 seconds) , and long period (one second). "With the completion of the latest Indonesian earthquake map in 2010, the computation of seismic load on the structure would be more accurate and efficient," said Sumaryanto.
This map has to accommodate all needs, from building construction, building of water, until the bridge. This map will support the provision of national infrastructure development and earthquake resistant. "Buildings and building, especially in earthquake prone areas, should be designed for earthquake resistance in accordance with this map," he said. "Design must enter the structure earthquake load factor which refers to a map of this earthquake. When ready to respond to the earthquake, both the number of victims and earthquake losses will be reduced."
Sumaryanto hope local governments can use this map as a reference in local development, including building regulations and licensing. Changes to national standards as a follow-up earthquake seismic zoning map was estimated to be completed in August. "We will also make microzonation, micro-scale seismic zoning, in order to know the condition of the soil surface and the vulnerability of buildings, so that the next Public Works has a list of the risk of damage caused by the earthquake," he said. "It's also useful in the emergency plan to reduce damage and losses caused by the earthquake."
Development investments in earthquake prone areas, said Irwan, it will become more expensive because the building may be established at the site must be strong enough to withstand the acceleration that may occur in the area. "But Japanese researchers have done studies that show that increasing investment in preparation, education, and to move people from vulnerable areas to safer areas, the fewer funds must be spent for reconstruction and rehabilitation of post-earthquake," he said.
