M 7.0 - 11 km NE of Bantay, Philippines

  • 2022-07-27 00:43:26 (UTC)
  • 17.521°N 120.818°E
  • 33.7 km depth

Tectonic Summary

On July 27, 2022, a magnitude 7.0 earthquake occurred in the northwestern portion of the island of Luzon in the Philippines. The earthquake occurred at shallow depths (approximately 10 km) and was the result of oblique reverse faulting. Initial analysis indicates that the earthquake occurred on oblique reverse fault either striking to the north or southwest. The earthquake depth, mechanism, and location are consistent with the earthquake having occurred in the Philippine Sea plate above the Sunda plate. The Sunda plate subducts eastward beneath Luzon with the plate boundary located off the western coast of Luzon.

The tectonics of the northern Philippines and around the island of Luzon are complex. Luzon is bounded to the east and west by subduction zones. In the southern part of Luzon, the subduction zone trench is located east of the island in the Philippines trench, and the Philippine Sea plate subducts westward beneath the Sunda plate. In the northern region of Luzon, where the July 27 earthquake occurred, the subduction zone location and direction changes, with the trench located west of Luzon and the Sunda plate subducting eastward beneath the Philippine Sea plate. The complexity of plate boundary interactions on and around Luzon is evidenced by the diversity of faulting mechanisms in large earthquakes. Magnitude 7 or greater earthquakes in this region since 1970 have exhibited reverse, normal, and strike slip faulting. These active plate boundaries lead to high seismicity rates. Since 1970, 11 other earthquakes of magnitude 6.5 or larger have occurred within 250 km of the July 27, 2022 earthquake. The largest of these earthquakes was a magnitude 7.7 strike slip earthquake on July 16, 1990 located approximately 215 km south of the July 27 earthquake. The 1990 earthquake killed at least 1,600 people and injured more than 3,000 people. The 1990 earthquake also caused landslides, liquefaction, subsidence, and sandblows in the Baguio-Cabanatuan-Dagupan area.

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