Crustal thickness beneath Central and East Java (Indonesia) inferred from P receiver functions

We compute receiver functions from teleseismic earthquake data recorded at the dense MERAMEX network in Central and East Java, Indonesia. In order to map the Moho depths H and the bulk crustal vP/vS-ratio κ we apply the H-κ stacking technique of Zhu and Kanamori (2000). Though the interpretation of the results is hampered by the high complexity of the recorded waveforms, in the context of a high noise level and of the heterogeneous assemblage of continental fragments and ophiolitic suture zones forming Southeast Asia, we were able to derive an average crustal thickness of about 34 km. Support for the assumption of ophiolitic basement in the center of the island related to the Meratus suture zone comes from shallowing of the Moho to about 30 km beneath the Kendeng zone. North and west of the Kendeng zone the Moho is imaged at anomalous depths down to 39 km. The observed anomalies line up along the hypothetical boundary between the continental SW Borneo fragment and the Meratus suture and are indicative of crustal thickening caused by overthrusting and compressional deformation in the context of a former collision zone. Resulting vP/vS-ratios cannot be inferred reliably due to the complexity of the waveforms. Our results do not corroborate the hypothesis of a major structural change along the southern coast at the division between Central and East Java. Likewise, we do not find clear evidence for the existence of the postulated Muria-Progo lineament.