![]() The crack that ruptured may have been on a slight diagonal, generating a small vertical motion, or it could have shifted some underwater topography structure like a seamount. That’s exactly what you would expect after an earthquake on a vertical crack, says McCloskey. They do not tend to lift much water.Įarlier today a buoy in the Bay of Bengal was reported to have sensed a 30 centimetre wave. In 2004, the 26 December Sumatran earthquake lifted trillions of tonnes of water by around 5 metres when the Sundra subduction fault ruptured.Įarthquakes on vertical cracks occur because two chunks of crust grind past each other horizontally, with little to no vertical movement. Last year’s Tohoku quake occurred in a subduction zone and lifted the seafloor by 10 to 20 metres. In subduction zones, earthquakes happen when mounting pressure causes one plate to suddenly pop up vertically. Vertical cracks also tend not to generate tsunamis. “We are still looking at very preliminary data but if everything stays the way it is looking now, this is an amazingly large event for this mechanism.” Non-tsunamigenic “I would have to check this but I don’t believe I’ve ever heard of an 8.7 vertical quake,” says McCloskey. Vertical transform faults take a shorter route to the mantle lower crust (see diagram).Īs a result, the energies released when vertical faults slip are generally smaller than subduction quakes. That’s because faults in subduction zones extend diagonally through the brittle crust and so travel greater distances before running into the viscous mantle lower crust beneath. This morning’s quake happened because one of them became active again.Įarthquakes on transform faults tend to be smaller than the great megathrust events generated, especially compared to megathrust events in subduction zones. These faults typically become inactive in older oceanic crust that is no longer at the ridge. As newly formed crust moves away from the ridge, it develops a series of cracks, or “transform faults”, that run perpendicular to the ridge. Vertical cracks like the one that ripped earlier today form at mid-ocean ridges, where oceanic crust is created. ![]() In 2018, a magnitude 7.5 quake rocked PNG's remote mountainous highlands, killing more than 100 people and damaging thousands of homes.The vertical orientation of the crack also explains why the quake did not generate a tsunami. There was no immediate threat to Australia, its Bureau of Meteorology said. The U.S tsunami warning system issued an alert after the quake but later said the danger had passed. State-backed communications provider PNG DataCo also reported impact to its undersea cable network, resulting in widespread disruptions. Power infrastructure was damaged in affected areas, causing an outage across the Eastern Highlands. The UN report said people had been injured by falling structures or debris, and there was damage to some health centers, homes, rural roads and highways. Papua New Guinea residents shared images and videos on social media of cracked roads, damaged buildings and cars, and items falling off supermarket shelves. Some of the injured were airlifted for immediate treatment. The regional power grid, internet cables, and the regional highway were damaged, but the airport is operational, it said. One person died in a landslide in Rai Coast, Madang, with three others buried in Wau, Morobe, the OCHA's PNG disaster management team said in a report posted on Twitter. While the government gave no death toll, the United Nations Office for the Coordination of Humanitarian Affairs (OCHA) in Asia and the Pacific said that at least 4 deaths and four injuries had been reported. Earthquakes are common in PNG, which sits on the Pacific Ocean’s "Ring of Fire," a hotspot for seismic activity due to friction between tectonic plates. The full extent of damage was not immediately clear as the location of the earthquake was remote. The quake hit about 67 km east of Kainantu and 80 kms north-west of Lae in the eastern PNG region, at about 9:45 am local time (2345 GMT Saturday), but was felt some 500 km (310 miles) away in the capital of Port Moresby. ![]() An earthquake of magnitude 7.6 struck eastern Papua New Guinea on Sunday killing at least four people, injuring others and damaging property and essential infrastructure.
0 Comments
Leave a Reply. |