The National Disaster Mitigation Agency on Saturday revised the death toll in the devastating earthquake upward to 389 people, from the 321 it reported the previous day, according to the Associated Press, as teams continue to sift through the rubble.
Scientists say the earthquake was so powerful it lifted the resort island of Lombok, Indonesia as much as 10 inches (25 centimeters) in the northwest of the island, near the epicenter of the quake, and in some places, dropped it by as much as 2-6 inches (5-15 centimeters).
Making a ground deformation map
Situated between the Indian and Pacific oceans, Indonesia is the world’s largest island country, with more than thirteen thousand islands. About 6,000 of the islands are inhabited.
Indonesia lies on the Pacific Ring of Fire where the Indo-Australian Plate and the Pacific Plate are pushed under the Eurasian plate where they melt at about 100 kilometers (62 miles) deep. The country has numerous volcanoes and frequent earthquakes.
Deformation is a change in the original shape of a material. When we are talking about earthquakes, deformation is due to stress and strain in the boundary zone between tectonic plates. Understanding the details of deformation and its effects on faults are important for figuring out which faults are most likely to produce the next earthquake.
Information acquired on ground deformation is data-driven, and a variety of methods are used, including LIDAR, the Global Positioning System (GPS), Interferometric Synthetic Aperture Radar (InSAR), creepmeters, and alinement arrays. All or some of these methods can give scientists a picture of deformation caused by an earthquake.
The ground deformation map of Lombok Island
Scientists from NASA and the California Institute of Technology’s joint rapid imaging project made a ground deformation map and measured changes in the island’s surface. Using synthetic aperture radar (SAR) data from the European Unionâ€™s Copernicus Sentinel-1A and -1B satellites, a map of Lombok Island was generated as viewed by the satellites over a six-day period covering July 30 through August 5.
It is important to note that the deformation actually occurred during the August 5 earthquake, according to NASA. The false-color deformation map is produced from automated interferometric processing of the SAR data using the JPL-Caltech ARIA data system in response to a signal received from the U.S. Geological Survey.
Looking at the map, the epicenter of the earthquake was centered at the northwest corner of the island. Based on the deformation patterns, scientists determined that the earthquake fault slip was on a fault beneath the northwestern part of Lombok Island – causing the almost 10-inch rise in the ground surface.
The map depicts motion towards the satellite (up and west) in the direction of the radarâ€™s line-of-sight, with contours every 2 inches (5 centimeters). The white areas are where the radar measurements weren’t possible, due to dense forests.
Almost 390,000 people, or about 10 percent of Lombokâ€™s population, are homeless or displaced after the earthquake, which damaged and destroyed about 68,000 homes. And as of Sunday, at least three districts in the north of the island have not received aid.
According to Fox News, Disaster agency spokesman Sutopo Purwo Nugroho said: â€œItâ€™s estimated the death toll will continue to grow because there are still victims who are suspected of being buried by landslides and collapsed buildings and there are deaths that have not been recorded.”