YOGYAKARTA-Tectonically, the Indonesian archipelago lies at the confluence of three tectonic plates of the world, namely Indo-Australian plate, Eurasian, and Pacific. Besides, there are many active faults in the Archipelago. This makes Indonesia an earthquake-prone area and vulnerable to tsunamis. "With this condition, of course we must be ready that we are vulnerable to disasters, including earthquakes," said Head of Community Development of Earthquake and Tsunami Operational Meteorology, Geophysics, and Climatology (BMKG), Jaya Murjaya, in a Workshop entitled Earthquake Disaster Risk Reduction through Earthquake Precursor Approach, which was held at Wisma MM of UGM, Tuesday (9/11).
In his presentation, Jaya Murjaya gave example of the joining of the Indo-Australian Plate with Eurasia plate along the west coast off Sumatra island to the south of Java, Nusa Tenggara, and the Banda Sea. These are the region with huge potential of powerful tectonic earthquakes which are very likely to trigger tsunamis. "Between 2009-2010, tsunami only happened 4 times in western Indonesian region, namely Tasikmalaya, Padang, Aceh, and recently Mentawai," he added.
To reduce the risk or the impact of super earthquake (including tsunamigenic earthquake), several studies need to be done. One of the studies is monitoring the 'precursor' in an area potential for big earthquakes. The past, current and future monitoring of 'precursor' done by BMKG are seismic monitoring, earth magnet, gravity, and other methods. "The 'precursor' monitoring study is one effort in order to start efforts in forecasting earthquake occurrence," said Jaya, who had served as BMKG Head of Yogyakarta.
Yogyakarta Governor Expert Staff for Development, Ir. Bayudono, M.Sc., added that 'precursor' or indication related to earthquakes can be continuously done so gradually it is able to predict earthquakes more accurately by various methods, such as by looking at gas emissions, gravity deformation of the earth surface, animal behavior, as well as surface of ground water. "It is still difficult to know about the time and location of earthquake, but the foreshadowing can be studied and distributed to the community," said Bayudono.
Strengthening earthquake indication is done by creating a network among many groups so the result is more accurate and better. On the other hand, the paradigm among people who face disasters, including earthquakes, should also be changed by making disasters as risk in human life. "Seeing these conditions, we can then prepare everything, such as rules of construction of earthquake resistant houses or settlements arrangement," said Bayudono.
Meanwhile, researcher from the Centre for Disaster Studies (PSBA), Universitas Gadjah Mada, Dr. Wahyudi, M.Sc., said one of the tools that has been developed to predict earthquakes is Atropatena. Atropatena is a detector with low-frequency of gravitational field, which appears before the earthquake.
Atropatena uses the basic principle of the torsion balance in the Cavendish experiment (an experiment to determine the gravitational constant G). This tool at least can record variation of the gravitational field due to the tectonic wave. According to Wahyudi, there are vast opportunities to develop sciences from Atropatena, so that finally it can be truly useful for the community. "Earthquake prediction cannot be done by Atropatena individually, but through a network. Currently, there are three Atropatenas in Azerbaijan, Pakistan, and Indonesia," said Wahyudi.
Evidence that earthquake quite often hits Indonesia can be seen, for example, this week earthquakes hit Yogyakarta twice. The first earthquake was 4 SR in Wonosari. The latest was 5.6 SR.