Deformation in the Leyte Geothermal Production Field, Philippines Between 1991 and 1999

Abstract

Global Positioning System (GPS) observations in Central Leyte, eastern Philippines, from 1991 to 1999 indicate considerable deformation along a segment of the Philippine Fault that cuts through the Leyte geothermal production field. Displacements computed at 9 core stations within the field, from 1991 to 1994, depict a left-lateral slip rate of about 2.6 cm/yr. A GPS survey conducted in 1998 at 10 sites within the geothermal field reveals the occurrence of a lower slip rate of about 1.3 cm/yr between the intervals 1994-1999. Though this suggests that less deformation has occurred during the last 4 years, our current GPS observations probably underestimate the true deformation field within the area. There is a need to apply network adjustments and address the problem of measurement uncertainties to our GPS data. The most recent GPS campaign forms part of a multi-agency project between the Philippines and Japan and is intended to complement results derived from SAR interferometry in studying crustal deformation and geologic hazards in the island of Leyte.