EARTHQUAKE ANALYSIS IN EAST JAVA, INDONESIA BETWEEN 1960 – 2017 USING MARKOV CHAIN MODEL

Abstract

Earthquake occurrence in East Java has been analyzed using a Markov Chain Model. The
catalog data comprised of earthquake events from East Java and its vicinity from 1960 until 2017. Data were
classified into subduction earthquake and inland fault earthquake. After that, the data were declustered using
Reasenberg (1985) algorithm for removing the aftershock. Spatial analysis was conducted by dividing the
research area into nine regions. Probability transition matrices which give information about the highest
probability transition of earthquake occurrence in each region were calculated for different magnitude
thresholds. Furthermore, the Chi-Square test was applied to examine the independence between earthquakes
occurrence. For seismic hazard analysis purpose, the temporal Markov chain analysis was employed by
determining the active (1) and inactive (0) period in each region based on the occurrence of earthquakes with
M ≥ 5 and depth d < 70 km. From the two-state probability transition, the mean duration of active and inactive
states in each region have been obtained. Both spatial and magnitude analysis results inferred that subduction
earthquake with M ≥ 4, M ≥ 5, and inland fault earthquake with M ≥ 3 exhibited strong first-order Markov
property, i.e. there was a robust dependency between an earthquake occurrence and the successive occurrence.
The mean duration of the inactive state in the research area varied from 2.5 until 13.5 years.