A Preliminary Result: Characteristic and Mechanism of Deep earthquake in Java subduction zone

Abstract

The occurrence of deep-focus earthquakes is unusual and has become one of mysterious seismic phenomena. The behavior of deep earthquake occurrence is still poorly understood. The geodynamical process of a deep earthquake must have a fundamental difference of physical processes from a shallow or intermediate earthquake. There are two main processes of deep earthquake occurrence, water infiltration into the subduction zone (dehydration embrittlement) and transformational faulting of metastable olivine. In Indonesia, the Java subduction zone is known as the deep earthquake source region. We will present preliminary results from the study of characteristic and geodynamical processes of deep earthquake events. We used catalog data from ISC-EHB and mechanism data from global CMT catalog within study area 3° - 13°S and 104,5° - 115°E. The activity of deep earthquakes in Java subduction showed 3 main characteristics i.e the seismicity decreases exponentially in 60 - 300 km depth, lack of earthquake activity due to hole structure in 330 - 500 km and increasing earthquake activity in 500-600 km depth due to transformational faulting of metastable olivine. Earthquakes' focal mechanism most varies at shallow depth, subsequently, focal mechanism transition occurred from reverse at 60-300 km to normal at >300 km depth.