institutions provided source parameters (location and depth) that were not in agreement. No information was present on the extent of the faulting or the direction of propagation and there was no link to the eruption of Mount Merapi. The USGS suggested that the focal mechanism was most likely associated with left-lateral slip on a NE trending strike-slip fault, as that is the orientation of the Opak Fault, but this has not been validated. No surface breaks were documented, but the location of the greatest damage that was caused does align with the Opak Fault as a possible source. A group of Japanese and Indonesian scientists visited the area in March 2007 and confirmed the lack of surface ruptures, and pointed out that any visible expression of the fault would likely have been rapidly destroyed due to the tropical climate, and have acknowledged the widely varying locations (and the preference for the Opak Fault) that were reported by the various seismological institutions. Their investigation resulted in a different scenario, with an unknown or newly formed NE trending fault as the origin of the shock. Evidence for one of the proposed faults was found in the form of alignment of portions of the Oyo River near the USGS' epicenter, which is parallel (N°65E) to the Nglipar fault in the Gunungkidul region. If the shock occurred in this area it could indicate the reactivation of a major fault system. The second proposed fault further to the east is nearly parallel to the Ngalang and Kembang faults that lie to the north of the Oyo River. InSAR analysis While the densely populated area that saw significant destruction is adjacent to the Opak River Fault, both the USGS and Harvard University placed the epicenter to the east of that fault. Few seismometers were operating in the region, but a group of temporary units that were set up following the mainshock recorded a number of aftershocks that were east of the Opak River Fault and were aligned along a zone striking N°50E. Due to the ambiguous nature of the available information on the source of the Yogyakarta earthquake, a separate group of Japanese and Indonesian scientists applied one of the first uses of interferometric synthetic aperture radar to determine the source fault. Several data sets (one captured in April 2006 and another post-earthquake batch from June) were collected from an instrument on board the Advanced Land