Preliminary report on crustal deformation surveys and tsunami measurements caused by the July 17, 2006 South off Java Island Earthquake and Tsunami, Indonesia

Abstract

A large earthquake (Mw=7.7) along a plate boundary occurred in the south of Java Island on July 17, 2006, and caused a significant tsunami. We made GPS observations and tsunami heights measurements during the period from July 24 to August 1, 2006. The earthquake seems to be due to an interplate low angle reverse faulting, though there might be a possibility of high angle faulting within the subducting lithosphere. Crustal deformation distribution due to the earthquake, aided by tsunami heights measurements, might clarify which would be the case. We occupied 29 sites by GPS in the area of southern Java encompassing the area from 107.8 E to 109.50 E. These sites were occupied once before the earthquake. However, we were not able to detect significant coseismic displacements. The obtained displacements, most of which span several years, show ESE direction in ITRF2000 frame. This represents the direction of Sunda block motion. The tsunami heights measured at 11 sites were 6-7 m along the southern coast of Java and indicate that the observed heights are systematically higher than those estimated from numerical simulations that are based on seismic data analysis. This might suggest that fault offsets might have been larger-nearly double-than those estimated using seismic analysis. These results lead us to an idea that the rupture was very slow. If this is the case, the earthquake might have been a "tsunami earthquake" that is similar to the one that occurred on June 2, 1994 in the east of the present earthquake.

Long aseismic slip duration of the 2006 Java tsunami earthquake based on GPS data

“…As suggested in a previous study (Ammon et al 2006), the 2006 Java earthquake was considered as ''tsunami earthquake'' based on the characteristics of its long rupture duration (Bilek and Engdahl 2007), low rupture velocity (Kato et al 2007), and the coseismic slip that occurred on shallow parts of the fault (Fujii and Satake 2006). In addition to those studies, our result of long decay postseismic deformation time supports the characteristic of a ''tsunami earthquake.''…”

“…1). This earthquake produced a devastating tsunami up to 7 m that caused casualties of more than 600 people and more than 50,000 people lost their houses (Kato et al 2007). …”

Waveform inversion for slip distribution of the 2006 Java tsunami earthquake by using 2.5D finite-difference Green’s function

“…A M w 7.7 (GCMT) earthquake occurred on July 17, 2006 (USGS PDE: 08:19:26.6, 9.284 S, 107.419 E, depth 20 km) far off the Java Island and generated large, devastating tsunamis: the inundation heights were about 6-7 m along the coast of the Java Island and about 500 persons drowned (Tsuji et al, 2006;Kato et al, 2007). The event is classified as a "tsunami earthquake" based on surface wave, body wave and tsunami wave analyses (Ammon et al, 2006;Fujii and Satake, 2006).…”

Discovery of possible mega-thrust earthquake along the Seram Trough from records of 1629 tsunami in eastern Indonesian region

“…Kato et al (2007) made GPS observations and tsunami height measurements during the event period, but no co-seismic displacement was detected. In their paper, the observed tsunami heights are systematically higher than those predicted from numerical simulations based on seismic wave analysis, which indicates that fault offset may be larger than estimates using seismic analysis and the rupture was very slow.…”