Applications of 2-D Resistivity
Surveys in Characterizations of Active Faults in Luzon: Implications
for Fault Occurrence Beneath the Bataan Nuclear Power Plant
Mario
Collado1 and Carlo A. Arcilla2
1Department
of Agriculture, Diliman, Quezon City
2National
Institute of Geological Sciences
University of the Philippines, Diliman, Quezon City
Abstract
Resistivity surveys have found wide
applications in determining groundwater levels and, when used with
other geophysicial and geological parameters, provide imaging of the
subsurface. Given the presence of active segments of the Marikina
Valley Fault system in Metro Manila, we conducted several resistivity
profiles across areas where there were visible surface ruptures due
to the fault. The intention was to test the usefulness of the
resistivity method in detecting the continuation of the fault beneath
the surface. We present 2-D inverted resistivity profiles across
active fault segments and demonstrate that there are enough
geophysical contrasts to distinguish the subsurface fault signature
with that of the bedrock. Since the controversial Bataan Nuclear
Power Plant is thought to be built on top of a fault, we employed
four resistivity lines around the building, using closely-spaced
electrodes in a Wenner array, in an attempt to image the fault if it
existed. Comparing results of the BNPP resistivity survey with our
numerous surveys on active faults, we conclude that there are no
anomalies that indicate faults or fractures underneath and along the
vicinity of the nuclear building. This study, however, DOES NOT
preclude the existence of fault/s close to the vicinity of the
nuclear building that may be outside the range of the resistivity
profile lines. The data presented, however, arguably rules out
the existence of a fault beneath the nuclear plant. It must be noted
that the “existence” of such a fault was one of the main
reasons why the BNPP was never operated.
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