20 Years On: How the Pangandaran Tsunami Struck and Its Lingering Threat

Twenty years ago, on July 17, 2006, a devastating tsunami struck Pangandaran and its coastline. The event followed a magnitude 7.7 earthquake centered in the waters south of West Java. Researchers from Indonesia's National Research and Innovation Agency (BRIN) and the Meteorology, Climatology, and Geophysics Agency (BMKG) have highlighted the potential for future tsunamis in the region.

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Before 2006, a tsunami earthquake in southern Pangandaran had occurred in 1921.

Eko Yulianto, a paleotsunami researcher at BRIN, noted that the southern coast of Pangandaran experienced a tsunami in 1921. He cited hypothetical calculations suggesting a recurrence interval of 675 years for a magnitude 9 or larger megathrust earthquake along southern Java, while smaller earthquakes could occur more frequently. Past smaller tsunami-triggering earthquakes were recorded in 1840, 1859, and 1994.

Pepen Supendi, a seismologist at BMKG, described the Pangandaran tsunami as one of the largest on Java, second only to the Banyuwangi tsunami. It arrived about an hour after the earthquake, between 4:15 PM and 4:30 PM Western Indonesian Time, with wave heights averaging 5 to 10 meters. The tsunami impacted a 250-kilometer coastline, reaching Cilacap and southern Yogyakarta, with waves continuing for hours across the Indian Ocean.

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The Pangandaran tsunami was among the largest on Java Island after Banyuwangi.

The earthquake's rupture process was slow, lasting three minutes at a shallow depth, which resulted in less dominant ground shaking. However, the 200-kilometer rupture was efficient in lifting the ocean floor because its epicenter was near a trench. The disaster claimed 405 lives, left 27 people missing, injured 274, and forced 13,198 people to evacuate, according to the Pangandaran Regional Disaster Management Agency (BPBD).

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The earthquake's rupture process was very slow, lasting 3 minutes and occurring at a shallow depth.