Conference Paper

FACTORS TRIGGERING LANDSLIDES IN TIMOR-LESTE

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Abstract

The main factor triggering landslide in Timor-Leste is rainfall. Therefore, landslide often occur during the rainy season. However, there is no information on earthquake-induced landslides or combined rainfall, although the tectonic activity cannot be ignored because Timor-Leste is located in a collision region with high seismic intensity. This paper aims to expose the ground instability and slope failure that are commonly triggered by torrential rainstorms and the influence of earthquakes due to topographical changes of the ground level. This is the preliminary study about topography change of the ground due to earthquake with minimum magnitude in Timor-Leste that occurred more than 10 years ago. The LOS (Line-of-sight) displacement obtained from InSAR (Interferometric Synthetic Aperture Radar) analysis shows that the occurrence times of ground deformation and earthquakes are related. Recent landslides triggered by rainfall that occurred on 17 January 2018 clearly show that high precipitation events do not trigger the landslides. On the other hand, the landslide occurred during four consecutive days after it rained, with a gradual increase from 4.2 mm/hour, 10.2 mm/hour, 13.6 mm/hour and 17.8 mm/hour, respectively

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Five suture zones are described from the zone of collision between the Eurasian, Indian–Australian and Pacific–Philippine Sea plates within the eastern Indonesia region. These are the Molucca, Sorong, Sulawesi, Banda and Borneo sutures. Each of these sutures has a relatively short history compared to most pre-Neogene orogenic belts, but each preserves a record of major changes in tectonics including subduction polarity reversals, elimination of volcanic arcs, changing plate boundaries, and important extension within an overall contractional setting. Rapid tectonic changes have occurred within periods of less than 5 Ma. Many of these events, although important, would be overlooked in older orogenic belts because the age resolution required to identify them, even when the evidence is preserved, is simply not possible.
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