More major quakes to hit Sumatra: Geologists

Muninggar Sri Saraswati and Sri Wahyuni, The Jakarta Post, Jakarta/Yogyakarta

The disastrous earthquake that generated deadly tsunami on Sunday has made Sumatra island more vulnerable to more major earthquakes in the future, the Indonesia Science Institute (LIPI) said on Thursday.

Geologist Danny H. Natawidjaja said that Sunday's earthquake had increased seismic activity on islands off Sumatra, including Simeulue, Nias, Siberut, Sipora and Pagai, that are the sources of earthquakes along the western part of Sumatra.

"The quake therefore increases chances for more major earthquakes there," he said.

The source of the 9.0-magnitude earthquake on Sunday was located near Simelue island.

Danny said the earthquake had also resulted in an increase in seismic activity on the Sumatra fault zone along the Bukit Barisan Mountains to Bengkulu, and increased the likelihood of volcanic activity across Sumatra, which has a number of active volcanoes.

"We are in a period of earth pressure accumulation that began after the last major earthquakes. The squeezing will continue until the next large earthquake," Danny said.

The west coast of Sumatra has many earthquake sources as it is located along an oceanic plate boundary.

"The earthquake (on Sunday) may now influence the nearby earthquake source in Nias," said Danny, who has been monitoring earthquakes in the regions for years,

LIPI, therefore, is currently focusing its observations of seismic activity on small islands in the western part of Sumatra, including Nias, to anticipate a recurrence of major earthquakes that last took place many years ago.

"A major earthquake may happen at any time to release energy that has been locked inside the earth for years. The energy comes from the earth's plates that squeeze very slowly against each other for decades or even centuries," Danny said.

According to Danny, small islands off the western part of Sumatra are moving toward the main island at the rate of five centimeters to 15 centimeters a year.

Previous massive earthquakes that have rocked the western part of Sumatra occurred in Simeulue in 2002, measuring 7.6 on the Richter Scale, on Pagai island in 2000 (7.8), in Nias in 1861 (8.5), and on Sipora island in 1833 (9.0).

Danny said LIPI had already installed 14 sensors equipped with Global Positioning System (GPS) technology on some islands and is to plant eight more on other islands in a bid to measure movements of the islands more accurately.

Deputy LIPI head Jan Sopahulewakan called on people in Sumatra and other parts of Indonesia to remain calm despite the possible increase in the number of earthquakes.

"We must accept that earthquakes are a part of our life. What we need to do is to anticipate possible risks resulting from these earthquakes, including tsunami," he said.

Separately, director of the Center for Earthquake Engineering, Dynamic Effect and Disaster Studies (CEEDEDS) at the Yogyakarta- based Indonesian Islamic University (UII), Sarwidi, suggested that the government establish safe-zone ranges and early warning system's in areas prone to tsunamis.

"Most of our regions have tsunami-prone areas," said Sarwidi, who is also a researcher and inventor of an earthquake-resistant building.

The zoning, he said, is needed to prevent people from constructing buildings in areas most at risk.

The zoning, he said, could be determined by calculating the declivity of the coastal areas and the magnitude of possible epicenters in the regions.

"Tsunami happen rarely, but they recur. I think this is a good time for the government to take action as soon as possible," Sarwidi said.