Землетрясение Pāhala, Hawaii

Tectonic Summary

The February 9, 2024, M5.7 occurred due to oblique reverse faulting at a depth of 37 km (23 miles). Large magnitude earthquakes in Hawaii that occur at this depth are typically caused by lithospheric flexure due to the weight of the Hawaiian Islands pressing down on the underlying oceanic plate. The February 9 event follows a classic mainshock-aftershock sequence that is typical of non-magmatically induced earthquakes. However, this earthquake did occur near a concentrated zone of long-term elevated seismicity rates within the mantle under the town of Pāhala; this zone has been particularly active since 2019, with some scientific studies linking it to active magmatic processes related to the deep plumbing of the Kīlauea and Mauna Loa volcanoes.

The Island of Hawaii is the youngest island in a chain of volcanoes that stretches about 5,500 km across the northern Pacific Ocean. The island chain results from a magma source that originates deep beneath the crust. The ocean crust and lithosphere above the magma source, within the Pacific tectonic plate, move to the northwest with respect to the deep magma source. Over millions of years, new island volcanoes are formed, and older volcanoes are carried away from the magma source (towards the northwest), erode, and eventually subside beneath sea level.

Non-volcanic or non-magmatic Hawaiian earthquakes reflect the long-term accumulation and release of lithospheric stresses rather than short-term processes associated with the motion of magma before or during an eruption. The long-term stresses are partly generated in the crust and mantle by the weight of the volcanic rock that composes the islands. In that sense, most Hawaiian earthquakes not directly associated with eruptions are nonetheless broadly related to volcanic activity.

Moderate-magnitude earthquakes are common in this part of Hawaii. Since 1990, there have been 16 other earthquakes M5+ within 50 km of the February 9, 2024, event. Hawaii has also experienced larger earthquakes, including the Mw 7.7 Kalapana earthquake in 1975 that occurred ~55 km to the northeast of the February 9, 2024, earthquake. The 1975 Kalapana earthquake generated a local tsunami that took 2 lives. Damage due to the 1975 earthquake and tsunami was estimated to total $4.1 million in Hawaii.