A three-dimensional model of the seismicity in the banda sea region

Abstract

Using the data of all registered tectonic earthquakes (independently from their magnitude) which occurred from 1st January 1918 to 31st December 1965, between 120° and 134°E and 2° and 10° S, a three-dimensional model of hypocenters and tectonic flux was constructed using a basic map and strong wires with small pearls on their tops. The pearls represent the earthquake foci while the length of the wires is proportional to the focal depth. The horizontal and vertical dimensions are equal in the model. More exact gross configurations, and consequently the main deformations of the descending slabs, were estimated by the spatial model of the inclined seismic zones (Benioff zones), provided that intermediate and deep shocks occur within the descending (oceanic) lithosphere. The spatial distribution of the tectonic flux in the period investigated, was illustrated by a series of maps (8 charts altogether), representing the tectonic flux distribution at different depths below the area considered. It was found that the most active center of the tectonic flux is related to the western margin of the Weber Basin, indicating that the deformations of the lithosphere are strongest here. The distribution of seismic energy according to the focal depth on the basis of a total of 181 shocks was also investigated. Its characteristics correspond to the pattern known to exist at and underneath typical island arcs, with an outstanding maximum between 0 and 70 km. A secondary maximum was found between 141 and 210 km. This paper is a contribution to the program of Working Group 1, Geodynamics of the Western Pacific—Indonesian Region, of the Inter-Union Commission on Geodynamics.