PORT MORESBY, September 21 — A magnitude 6.4 earthquake struck Papua New Guinea at 9:17 a.m. UTC, the U.S. Geological Survey reported, shaking communities across an island nation that sits on one of the most seismically active stretches of the planet. The quake was centered roughly 30 miles from Kainantu, a town in the Eastern Highlands, and occurred at a depth of about 64 miles (103 kilometers), according to the USGS. No casualty or damage figures were immediately available.
The agency said the population in the affected area resides in structures that are a mix of vulnerable and earthquake-resistant construction. That detail matters for how a quake of this size translates into damage on the ground.
The USGS also noted that recent earthquakes in this region have caused secondary hazards such as landslides and liquefaction. Depth is a factor. At roughly 103 kilometers down, the rupture sits well below the surface, which can damp the shaking felt at ground level compared with a shallower event of the same magnitude.
A fault system 2,500 miles long
The quake struck on the Australia-Pacific plate boundary, a fault system about 2,500 miles long that spans from the Sunda (Java) trench in the west to the Solomon Islands. Papua New Guinea sits along the Pacific Ring of Fire, where the Pacific Plate meets many surrounding tectonic plates. The numbers on that belt are stark.
About 90% of the world’s earthquakes and around 75% of its active volcanoes are located along the Ring of Fire. The region contains roughly 452 volcanoes and stretches for about 25,000 miles, forming a horseshoe-shaped belt that runs from the southern tip of South America, along the western coasts of North and Central America, across Alaska and Russia, and then through Japan, the Philippines, Indonesia, Papua New Guinea and New Zealand.
Papua New Guinea has recorded 13 magnitude 7.5 or greater earthquakes since 1900. In April 2007, a magnitude 8.1 earthquake occurred, triggering a tsunami and killing at least 40 people, according to the USGS.
Same day, a smaller event in Italy
The same day as the Papua New Guinea quake, a magnitude 4.5 earthquake hit Italy, causing a television to fall off a wall and items to fall off shelves at a cafe in Pozzuoli, near the quake’s epicenter. The Italy event was reported in a 00:17 file. The two events are not connected, but they illustrate how routinely the planet’s fault systems move.
Scientists monitor the Pacific Ring of Fire closely for secondary hazards and potential tsunami generation. What to watch next is whether the USGS or local authorities revise the magnitude or issue assessments of shaking intensity and landslide risk for the Kainantu area.
For now, the agency’s account stands as the fullest public picture of an event that struck deep, far from the capital, and left no immediate report of harm.
