Papua New Guinea M 7.5 – Feb 25, 2018 at 17:44:43 UTC

“The February 25, 2018, M 7.5 earthquake occurred as the result of thrust faulting at shallow a depth. Preliminary focal mechanism solutions indicate slip occurred on either a moderately dipping fault striking west-northwest, or on a moderately dipping fault striking southeast. At the location of this earthquake, the Australia plate is converging with the Pacific plate, moving towards the east-northeast with respect to Pacific lithosphere at a velocity of approximately 107 mm/yr. Earthquakes in this geographical region are generally associated with the large-scale convergence of these two major plates, and with the complex interactions of several associated microplates, most notably the South Bismarck plate, the Solomon Sea microplate, and the Woodlark plate. The location, depth, and focal mechanism solution of this earthquake are consistent with it occurring as intraplate faulting within the crust of the Australia plate.

While commonly plotted as points on maps, earthquakes of this size are more appropriately described as slip over a larger fault area. Thrust-faulting events of the size of the February 25th, 2018 earthquake are typically about 85×30 km (length x width).

Papua New Guinea experiences a high rate of seismic activity, with 23 other events of M 6+ occurring within 250 km of the February 25, 2018 earthquake over the preceding century. The closest of these was a M 6.2 earthquake in August 1993, about 17km to the north of today’s earthquake. The largest was a M 7.2 event in June 1986, 230 km to the north-northeast on or near the Australia:Pacific plate boundary in the region. With the exception of a M 7.5 earthquake at intermediate depth (186 km) in eastern Papua New Guinea in February 1963 (which occurred on the subduction zone at depth), all prior M 7.5+ earthquakes in this region have been associated with the shallow subduction zone plate boundaries in northern New Guinea. The vast majority of moderate-to-large earthquakes in this region are not known to have caused significant damage or casualties, though few have been as large as today’s earthquake. A M 7.1 earthquake in June 1976, 340 km to the northeast of this event, resulted in over 400 shaking related deaths. Landsliding also caused a significant number of additional fatalities in that event.”

The quake as captured by AM.R8C73.00.SHZ in Exton PA (RaspberryShake 1D).
Distance: 14,651 km
Azimuth: 39.5 deg