LITHOLOGICAL IDENTIFICATION OF DEVASTATED AREA BY PIDIE JAYA EARTHQUAKE THROUGH POISSON’S RATIO ANALYSIS

Abstract

A combination of geophysical methods has been applied in the earthquake-devastated area in
late December of 2016 in Pidie Jaya Regency, Aceh Province, Indonesia. The methods are refraction seismic
and Multichannel Analysis Surface Wave (MASW). This research aims to identify the types of near-surface
lithologies through Poisson’s ratio analysis. These velocity values were acquired through measurements in
three sites among the devastated areas. The measurement of VP and VS values deploys the PASI 16S
Seismograph with 24 channels. The geometry of seismic refraction lines was designed by placing 2-meter long
geophone intervals, and nine total shot points were inserted, while in VS data measurement, the geophone
intervals were the same set as the refraction seismic with differently laid out geometry of shot points and total.
Both data were processed using ZondST2D for the 2D profile of VP and SeisImager for 2D section of VS. The
result of the study indicated that all of the Poisson’s ratio profiles show lithology consisting of clayey sand,
clay and saturated clay with a value generally ranging from 0.22 to 0.46. The clay lithology is a prominent
finding of this research. These interpretations more or less match other results even though some are in different
research areas. This finding was proven by the damaged area affected by the earthquake in late 2016. Thus the
result can be beneficial to designing and customizing building types according to lithological characteristics
then mitigating from the forthcoming threat of the earthquake.