Venezuela M7.3 August 21, 2018 at 21:31:46 UTC

Position:10.855°N 62.883°W – Depth:154.3 km

While this event had a magnitude of 7.3, and was felt throughout the eastern Caribbean, there was little major damage due to the 150km depth.

From the USGS Summary of this event:

“The August 21, 2018, M 7.3 earthquake near the northern coast of Venezuela occurred as the result of oblique reverse faulting at intermediate depth. The focal mechanism solution indicates slip occurred on either a steep fault striking east-west, or on a shallow structure striking southeast. At the location of the earthquake, the South America plate moves westward with respect to the Caribbean plate at a rate of approximately 20 mm/yr. The South America plate begins its subduction beneath the Caribbean plate about 550 km to the east of today’s earthquake and reaches depths close to 150 km in the vicinity of this event. This earthquake occurred near the southern end of the Caribbean subduction zone. At shallow depth, the plate boundary in this region transitions to transform faulting along the San Sebastian – El Pilar fault system. The depth and focal mechanism solution of today’s earthquake is consistent with faulting at depth, within subducted lithosphere of the South America plate, rather than along the shallow right-lateral transform plate boundary.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Oblique-thrust-faulting events of the size of the August 21st, 2018 earthquake are typically about 65×25 km (length x width).

Earthquakes like this event, with focal depths between 70 and 300 km, are commonly termed “intermediate-depth” earthquakes. Intermediate-depth earthquakes represent deformation within subducted lithosphere rather than at the shallow plate interfaces between subducting and overriding tectonic plates. They typically cause less damage on the ground surface above their foci than is the case with similar-magnitude shallow-focus earthquakes, but large intermediate-depth earthquakes may be felt at great distance from their epicenters. Earthquakes have been reliably located to depths close to 180 km in this region.

While there have been 17 previous M 6+ earthquakes in this region, large earthquakes are rare; this is the largest historic event within 250 km of this location in the 20th and 21st centuries. All prior damaging earthquakes in this region have been shallow.”