| 1938 Banda Sea earthquake | |
| Timestamp: | 1938-02-01 19:04:23 |
| Isc-Event: | 902352 |
| Anss-Url: | official19380201190422_30 |
| Local-Time: | 04:04 |
| Magnitude: | 8.5-8.6 |
| Intensity: | |
| Depth: | 60km (40miles) |
| Location: | -5.05°N 131.62°W |
| Type: | Oblique-slip |
| Tsunami: | Yes, |
| Aftershocks: | Yes |
| Casualties: | None |
The 1938 Banda Sea earthquake occurred on February 2 at 04:04 local time with an estimated magnitude of 8.5-8.6 on the moment magnitude scale. Shaking was intense with an assigned Rossi–Forel intensity of VII (Very strong tremor) and intensity of VI (Strong) on the Modified Mercalli intensity scale. This oblique-slip event generated a destructive tsunami of up to 1.5 metres in the Banda Sea region, but there were no deaths.
The Banda Sea is located within a very complex tectonic regime that accommodates the convergence between the Australian Plate and the Sunda Plate. The Molucca Sea Plate, Bird's Head Plate, Timor Plate, and Banda Sea Plate all help accommodate the elaborate plate boundary system in the region. This collection of microplates leads to large amounts of seismicity in the area, including the 1852 Banda Sea earthquake which was potentially a 8.8 event, as well as the 1629 Banda Sea earthquake which was also estimated at up to 8.8.
At around 04:00 local time, a large earthquake started to shake the Banda islands. The earthquake was assigned a moment magnitude of 8.5–8.6 and caused a destructive tsunami of at the Kai islands. The tsunami expected for an earthquake of this size is much greater, such as of those in 1629 and 1852, however this earthquake occurred at a depth of 60km which impeded much of the ocean floor displacement which leads to a tsunami. Due to its depth, the earthquake was felt strongly in far away Darwin and as far as Merauke and Daly Waters. In Darwin, concrete floors cracked and windows were damaged. This earthquake is of significant scientific interest as it remains a mystery as to precisely which fault produced this earthquake. Some studies consider this earthquake the largest intraslab earthquake on record.
Despite being a large thrust faulting event, the tsunami was rather small. This is assumed to be caused by the 60 kilometer depth. At the Kai islands, runups of were recorded. Beachfront damage was reported across the Tayandu Islands and the entire Banda region.