Tectonic Summary

The August 2, 2019, M 6.9 earthquake off the western end of the Indonesian island of Java occurred as the result of oblique reverse faulting, near the boundary between the Australia and Sunda plates. Focal mechanism solutions for the event indicate rupture occurred on either a moderately dipping fault striking towards the SSW, or on a moderately dipping fault striking towards the ENE. At the location of this earthquake, the Australian plate is moving northeast relative to the Sunda plate at a rate of approximately 60 mm/yr. The Australia plate begins subducting beneath the Sunda Plate at the Sunda-Java trench, approximately 100 km southwest of this earthquake. The location, depth and preliminary focal mechanism solution for this earthquake indicate the event likely occurred within the subducting lithosphere of the Australia plate, rather than on the shallower interplate thrust boundary.

The plate boundary region between the Australia and Sunda plates is highly seismically active, with past strong earthquakes having occurred within each of the Australia and Sunda plates as well as on the plate interface. Two earthquakes above M 7.0 have occurred within 250 km of this event within the past century, including a M 7.1 and M 7.6 events in 1943 and 1933, respectively. Further afield, the M 7.8 earthquake of June 2, 1994, and the M 7.7 earthquake of July 17, 2006, both of which occurred south of Java and both of which produced destructive tsunamis, occurred as the result of thrust faulting on the shallow plate interface near the Sunda-Java Trench. The devastating Yogyakarta earthquake of May 26, 2006, M 6.3, occurred at shallow depth within the overriding Sunda plate, 600 km to the east of the August 2, 2019 event, killing more than 5000 people. The M 7.5 Java earthquake of August 28, 2007, occurred at a depth of about 290 km within the subducted Australia plate, 325 km to the northeast of today’s event.

Event Details

Event Map

Tectonic Summary

Tectonic Summary

Historical Magnitude 4.5+ (100km)