Note on seismicity of the Bali convergent region in the eastern Sunda Arc, Indonesia

Local events occurring in the period from 1991 to 1998 around the Bali region in the eastern part of the Sunda arc have been relocated using data from the local seismic network operated by the Meteorological and Geophysical Agency (MGA) of Indonesia. The quality of hypocentres is generally good within a radius of about 200 km from the centre of the network. The hypocentre distribution shows that seismic activities are concentrated down to a depth of about 200 km, not only along the forearc region but in the backarc region as well. The stress field of the crustal layer around Bali shown by the fault-plane solution is dominated by compression in a north – south direction in agreement with the direction of the convergence between the Eurasian and Indo-Australian Plates. Thrust events occurring in the backarc region to the north of Bali are likely to be due to the westward extension of the backarc thrust fault of Sumbawa and Flores. The hypocentres of local earthquakes recorded by MGA seismographic stations form an image of southward subduction of the oceanic crust underlying the Java Sea that is in the opposite direction of the main subduction of the Indo-Australian Plate.