An earthquake occurred on July 17, 2006, at 15:19:27 local time along a subduction zone off the coast of west and central Java, a large and densely populated island in the Indonesian archipelago.

Other factors may have contributed to exceptionally high peak runups of 10–21 m (33–69 ft) on the small and mostly uninhabited island of Nusa Kambangan, just to the east of the resort town of Pangandaran, where damage was heavy and a large loss of life occurred.

The July 2006 earthquake had an unusually slow rupture velocity which resulted in minor shaking on land for around three minutes, but the intensity was very light relative to the size of the tsunami that followed.

The unusually low felt intensities, along with the short period body wave magnitudes, were components of the event that narrowed its classification into that of a tsunami earthquake.

When longer period signals of around 250 seconds were investigated, the shock was reevaluated to have a moment magnitude of 7.6, with a hypothesis that the slow nature of the slip of the event may have concealed its substantial extent.

Sediment was thought to have contributed to a slower rupture, due to a lubrication effect at the plate interface, with the result being an earthquake signature that had abundant long period seismic signals, which could be an important factor in the tsunami-generation process.

[14] A 300 km (190 mi) portion of the southwest and south-central Java coast was affected by the tsunami, and resulted in around 600 fatalities, with a high concentration in Pangandaran.

Within three weeks of the event, scientists from five different countries were on the ground in Java performing a survey of the affected areas, including gathering runup (height above normal sea level) and inundation (distance the surge moved inland from the shore) measurements.

The (sea floor) bathymetry in the area supported a proposition that a canyon slope failure or an underwater landslide may have contributed to or focused the tsunami energy at that location.

Nineteen farmers and one prisoner were killed there, but the deep water port of Cilacap (just to the east) was protected by the island, although one large moored vessel made ground contact during the initial 1.5 m (4 ft 11 in) withdrawal.

Hotels and some houses and shops that were of reinforced brick construction were far better off, because units that were exposed to a flood depth of 3–4 meters (9.8–13.1 ft) were considered repairable.

Virtually no time was available to make that sort of effort (had the intention been to communicate the danger with the public) because some community leaders were sent text messages with pertinent information only minutes prior to the arrival of the first waves.

Trained research teams were already on the ground on Java responding to the May earthquake and began a survey of more than one hundred Muslim farmers, plantation laborers, and fishermen (or those with fishing-related occupations) that were affected by the tsunami.

For rescue, shelter, clothing, and locating missing people, individuals were listed as the primary provider, but 100% of those surveyed replied that the government should be responsible for relief.