Bracing for disaster

MMI Ahyani, Bandung

The massive earthquake and subsequent tsunami that hit Aceh and other countries sharing the Indian Ocean on Sunday, claiming thousands of lives, reminds us that we truly live in a geographically hazardous area.

The entire southern part of Indonesia, starting from Sumatra, Java, Bali, Nusa Tenggara to Maluku and Papua and also the northeastern part of the country -- Sulawesi and North Maluku -- constitute active seismo-tectonic regions. Potential volcanic dangers exist at places along these lines.

Geological technology has been able to map out areas vulnerable to geological disasters, such as earthquakes, tidal waves, volcanic eruptions, landslides and the like. However, it is still impossible to predict when these disasters will actually hit. Even if a natural disaster is predicted, the accuracy rate is far from satisfactory. In some cases, scientists making such wrong predictions can even be charged with a criminal offense for "disrupting public order and security."

Prior to the recent tragedy, a seismologist from the Center for Geotechnological Research and Development of the Indonesian Institute of Sciences in Bandung, Danny H. Natawidjaya, issued a soft "warning" in this respect during a discussion on the geology of the Sunda Straits held in Bandung in December 2003.

He said that based on geological research and seismic cycle records, the possibility of an earthquake measuring 9.0 on the Richter Scale around the subduction zone in the west of Sumatra was at the end of its 200-year cycle.

He noted that geological research around Mentawai showed that the area was hit by major earthquakes in 1381, 1608 and 1833.

Experts have paid a lot of attention to areas around Mentawai and Siberut because of their history of major earthquakes that occur in 200-300 year cycles.

This means of course that a major earthquake could hit this area sometime in the next 50 years. A number of earthquake monitoring devices have been placed around the Mentawai and Siberut group of islands.

Existing geological data shows that seismic activity in the subduction zone of the Mentawai island group have raised them by some 2 meters. In Mentawai alone, six global positioning satellite stations have been installed to monitor the movement of tectonic lithospheric plates.

Data obtained from these stations shows that the islands in Mentawai have moved three to four centimeters towards Sumatra each year. The conclusion is that energy is continuing to accumulate in this subduction zone. Over time, this accumulated energy must be released through an earthquake.

Speaking here on Monday about his prediction, Danny instead remarked that the recent earthquake was not one that he had predicted would occur. Thus it is highly likely that another similar quake will happen sometime in the next 50 years.

Danny added that movements on the bed of the Indian Ocean can cause tension on either side of the fault line.

If the accumulation of tension and energy at the sides of the tectonic lithospheric plates or the subduction zone becomes unbearable, more fresh earthquakes may occur.

Given this information the public should remain alert and prepared for potential earthquakes.

This is not a time for blame, though. The expensive lessons we have learnt must enlighten us to prepare for future disasters.

Of no less importance is to prepare communities living in disaster prone areas with adequate knowledge.

The writer is a freelance journalist based in Bandung who has a special interest in environmental and earth affairs.