The Advanced Rapid Imaging and Analysis (ARIA) team at NASA's Jet Propulsion Laboratory in Pasadena, California, and Caltech, also in Pasadena, created this Damage Proxy Map (DPM) depicting areas in the northeastern part of Lombok Island, Indonesia, that are likely damaged (shown by red and yellow pixels) as a result of the major earthquake sequence (including the M6.4 July 29, the M6.9 August 5, the M5.9 August 9, and the M6.4 August 18 earthquakes) in 2018. The map is derived from synthetic aperture radar (SAR) images from the ALOS-2 satellites, operated by Japan Aerospace Exploration Agency (JAXA). The images were taken before (May 13, 2018 00:30) and after (August 19, 2018 00:30, both local time) the earthquakes.
The map covers an area of 73 by 70 kilometers, shown by the large red polygon. Each pixel measures about 30 meters across. The color variation from yellow to red indicates increasingly more significant ground surface change. Preliminary validation was done by comparing with the DigitalGlobe's high-resolution optical satellite imagery. This damage proxy map should be used as guidance to identify damaged areas, and may be less reliable over vegetated areas. For example, the scattered single colored pixels over vegetated areas may be false positives, and the lack of colored pixels over vegetated areas does not necessarily mean no damage.
The DPM was created by the NASA-JPL/Caltech ARIA team, and the ALOS-2 data were provided by JAXA. The Earth Observatory of Singapore coordinated with the Sentinel Asia to timely task the ALOS-2 satellite. The algorithm development was carried out at JPL under a contract with NASA.
For more information about ARIA, visit: http://aria.jpl.nasa.gov