PORT MORESBY, Papua New Guinea, April 11 (UPI) -- A 7.1 magnitude earthquake struck southwest of Panguna, Papua New Guinea, on Friday, with no reported casualties.
A 6.5 magnitude aftershock followed an hour later, approximately 25 kilometers southeast of the mainshock.
The U.S. Geological Survey said the earthquake was caused by "thrust faulting on or near the subduction zone interface between the subducting Australia plate and overriding Pacific plate."
The earthquake zone, within 250 kilometers of Friday's quake, is considered "very active seismically," with 35 reported earthquakes measuring more than 7 on the moment magnitude scale over the last century.
[U.S. Geological Survey]