An open question in volcano science is whether and how earthquakes trigger volcanic eruptions. It is well known that there is a short-term interaction related to the passage of the seismic waves (minutes to days after the earthquake) but it is not understood whether there is an intermediate-term or a long-term interaction (weeks to month or month to decades after the earthquake). This project uses satellite interferometry to survey the volcanic activity in Sumatra before and after the 2004 and 2005 earthquakes to answer this question. The earthquakes were among the largest-ever instrumental earthquakes and provide a unique opportunity to investigate eruption triggering because they were associated with significant decompression of the volcanic arc. The InSAR survey tests the hypothesis that earthquake-induced decompression triggers eruptions. The rationale of this project is that new volcanic activity is associated with the ascent of magma from deep sources towards the surface and thus detectable by precise space geodetic measurements.
In the first phase of the project 2005-2010 imagery of the Canadian Radarsat-1 and the Japanese ALOS satellite will be analyzed to detect any anomalous surface deformation that occurred after the earthquakes. In the second phase 1993-1998 imagery from the JERS-1 satellites will be analyzed to map surface deformation prior to the earthquakes. Comparison of pre-earthquake with post-earthquake data will identify triggered volcano deformation. This project is a partnership between the University of Miami and the Institute of Technology in Bandung (ITB), Indonesia. ITB will lead ground-based investigations of satellite-detected active centres in collaboration with Indonesian government and research institutions.
In this project we used satellite data to study active volcanoes in Indonesia’s west Sunda arc. We used a technique called Interferometric Synthetic Aperture Radar (InSAR) to investigate deformation prior to the eruption of the volcanoes. The study uncovered evidence that several volcanoes did in fact ‘inflate’ prior to eruptions due to the rise of magma. The fact that such deformation could be detected by satellite is a major step forward in volcanology; it is the first unambiguous evidence that remotely detected ground deformation could help to forecast eruptions at volcanoes. The study was published in an article in the Geophysical Research Letters in 2012. Surveying entire volcanic regions using satellite data?is of primary importance to the detection of ground? deformation prior to the onset of eruptions. If volcanic? inflation is observed, it can help us to predict where ?the next eruption may occur. Moreover, in regions like ?Indonesia, where volcanoes are prevalent and pose a threat to millions of people, and where ground-based monitoring is sparse, remote sensing via satellite could become a major forecasting tool. Analyzing more than 800 InSAR images from the Japanese Space Exploration Agency’s ALOS satellite, we surveyed 79 volcanoes in Indonesia between 2006 and 2009. We detected deformation at six volcanic centers, three of which erupted after the observation period, confirming that inflation is a common precursor of volcanic eruptions at west Sunda volcanoes. The monitoring of changes to the Earth’s surface helps us to better predict the onset of volcanic activity, which can have devastating impacts on human life. Like with earthquakes and tsunamis, however, we cannot predict activity with certainty, but we hope that new tools like satellite remote sensing will help us to gather critical information in near real-time so we can anticipate the risk of eruptions and deploy resources in a timely manner. In another study we used the same type of data to study land subsidence in Indonesian urban areas. We found that Jakarta and several other major Indonesia cities are sinking at alarming rates of up to 22 cm per year. This rapid land subsidence of major cities, due to extraction of groundwater for industrial use, is likely to put the densely populated coastal regions below sea level in less than two decades. The study was published in the early online edition of the journal Remote Sensing of Environment. This project used imagery from the ALOS-1 satellite of the Japanese Space Exploration agency (JAXA). The imagery was provided by the Alaska Satellite Facility (ASF) through the United States Government Research Consortium (USGRC).
