Earth, Planets and Space

, Volume 59, Issue 10, pp 1067–1071 | Cite as

Gravity basement of the Guinsaugon landslide along the Philippine Fault Zone

  • Masahiko Makino
  • Allan A. Mandanas
  • Sandra G. Catane
Open Access
Article

Abstract

A gravity survey was conducted in Guinsaugon, St. Bernard, Southern Leyte, Philippines, to determine the subsurface structure of the Leyte segment of the Philippine Fault Zone (PFZ), where a massive landslide killed 1119 villagers on 17 February 2006. The landslide started on top of a 780-m-high ridge linked with the PFZ. The build-up of pore pressure in the slope due to saturation and possible earthquake-triggered ground shaking along the PFZ, may have initiated the landslide. A two-dimensional structure using homogeneous density models was applied to interpret the gravity anomalies in the Guinsaugon landslide. The most suitable model depicts a deep, narrow graben filled with low-density sediments. The graben is 1.5 km wide and 2 km deep and has a density contrast of -0.4 g/cm3. The western boundary of the graben is steep and coincides with the terminus (southern) Leyte segment of the PFZ. The existence of a deep-seated seismically active fault at the foot of the steep slopes and the soft sediments in the narrow graben are important factors in understanding the trigger and failure mechanisms of the landslide and in the assessment of hazards and risks due to landslides and earthquakes.

Key words

Gravity landslide Guinsaugon Philippine Fault Zone earthquake 

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Copyright information

© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2007

Authors and Affiliations

  • Masahiko Makino
    • 1
  • Allan A. Mandanas
    • 2
  • Sandra G. Catane
    • 2
  1. 1.Geological Survey of JapanAISTTsukubaJapan
  2. 2.National Institute of Geological SciencesUniversity of the PhilippinesQuezon CityPhilippines

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