May 20, 2013 – KAMCHATKA – A massive earthquake swarm has occurred in the region of Petropavlovsk-Kamchatskiy, Russia. More than 20 earthquakes have struck the region in the last 22 hours- the strongest of which was a 5.9 magnitude earthquake, which rattled the seafloor at a depth of 16.5 km deep. The latest seismic flare-up along this region reflects growing agitation on one of the planet’s largest tectonic plates- the Pacific plate. Increasing seismic volatility along this region of Kamchatka could have serious ramifications for every tectonic plate that comes into contact with the Pacific plate- from the South Pacific to South America. A similar, more intense earthquake swarm occurred along the periphery of the Pacific Plate near the Santa Cruz Islands in February of this year. Is the Pacific plate on the verge of a large-scale change?
The geology of the region: The Kuril-Kamchatka arc extends approximately 2,100 km from Hokkaido, Japan, along the Kuril Islands and the Pacific coast of the Kamchatka Peninsula to its intersection with the Aleutian arc near the Commander Islands, Russia. It marks the region where the Pacific plate subducts into the mantle beneath the Okhotsk micro-plate, part of the larger North American plate. This subduction is responsible for the generation of the Kuril Islands chain, active volcanoes located along the entire arc, and the deep offshore Kuril-Kamchatka trench. Relative to a fixed North America plate, the Pacific plate is moving towards the northwest at a rate that increases from 75 mm/year near the northern end of the arc to 83 mm/year in the south. Plate motion is predominantly convergent along the Kuril-Kamchatka arc with obliquity increasing towards the southern section of the arc. The subducting Pacific plate is relatively old, particularly adjacent to Kamchatka where its age is greater than 100 Ma. Consequently, the Wadati-Benioff zone is well defined to depths of approximately 650 km. The central section of the arc is comprised of an oceanic island arc system, which differs from the continental arc systems of the northern and southern sections. Oblique convergence in the southern Kuril arc results in the partitioning of stresses into both trench-normal thrust earthquakes and trench-parallel strike-slip earthquakes, and the westward translation of the Kuril forearc. This westward migration of the Kuril forearc currently results in collision between the Kuril arc in the north and the Japan arc in the south, resulting in the deformation and uplift of the Hidaka Mountains in central Hokkaido. The Kuril-Kamchatka arc is considered one of the most seismically active regions in the world. Deformation of the overriding North America plate generates shallow crustal earthquakes, whereas slip at the subduction zone interface between the Pacific and North America plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Kuril-Kamchatka arc earthquakes occur within the subducting Pacific plate and can reach depths of approximately 650 km. -USGS
April 20, 2013 – SICHUAN, CHINA – A strong 6.6 magnitude earthquake hit a remote, mostly rural and mountainous area of southwestern China’s Sichuan province on Saturday, killing at least 203 people and injuring about 11,500 close to where a big quake killed almost 70,000 people in 2008. The earthquake, China’s worst in three years, occurred at 8.02 a.m. (0002 GMT) in Lushan county near Ya’an city and the epicenter had a depth of 12 km (7.5 miles), the U.S. Geological Survey said. The quake was felt by residents in neighboring provinces and in the provincial capital of Chengdu, causing many people to rush out of buildings, according to accounts on China’s Twitter-like Sina Weibo microblogging service. State media said 156 people had been confirmed dead with more than 5,500 injured. President Xi Jinping and Premier Li Keqiang said all efforts must be put into rescuing victims to limit the death toll. After arriving at the disaster zone by helicopter, Li directed earthquake relief efforts from a plaza in Longmen Township in Lushan, Xinhua said. Li asked that a road be opened to Baoxing County, one of the most affected by the earthquake, and that rescuers “act quickly” in their efforts, Xinhua quoted Li as saying. “The current most urgent issue is grasping the first 24 hours since the quake’s occurrence, the golden time for saving lives,” Xinhua news agency quoted Li as saying earlier. Xinhua said 6,000 troops were heading to the area to help with rescue efforts. State television CCTV said only emergency vehicles were being allowed into Ya’an, though Chengdu airport had reopened. Most of the deaths were concentrated in Lushan, where water and electricity were cut off. Pictures on Chinese news sites showed toppled buildings and people in bloodied bandages being treated in tents outside the hospital, which appeared only lightly damaged. Rescuers in Lushan had pulled 32 survivors out of rubble, Xinhua said. In villages closest to the epicenter, almost all low rise houses and buildings had collapsed, according to footage broadcast on state television. “We are very busy right now, there are about eight or nine injured people, the doctors are handling the cases,” said a doctor at a Ya’an hospital who gave her family name as Liu. The hospital was seeing head and leg injuries, she added. The China Meteorological Association warned of a possibility of landslides occurring in Lushan county on Saturday and Sunday, the agency said in a statement on its website. A resident in Chengdu, 140 km (85 miles) from Ya’an city, told Xinhua he was on the 13th floor of a building when he felt the quake. The building shook for about 20 seconds and he saw tiles fall from nearby buildings. Ya’an is a city of 1.5 million people and is considered one of the birthplaces of Chinese tea culture. It is also the home to one of China’s main centers for protecting the giant panda. “There are still shakes and tremors and our area is safe. The pandas are safe,” said a spokesman with Ya’an’s Bifengxia nature park, a tourism park that houses more than 100 pandas. Shouts and screams were heard in the background while Reuters was on the telephone with the spokesman. “There was just an aftershock, an aftershock, our office is safe,” he said. Numerous aftershocks jolted the area, the largest of which was magnitude 5.1. Sichuan is one of the four major natural-gas-producing provinces in China, and its output accounts for about 14 percent of the nation’s total. The U.S. Geological Survey initially put the magnitude at 7, but later revised it down. The devastating May 2008 quake was 7.9 magnitude. –
January 22, 2013 – PAPUA NEW GUINEA – Eruptions of Papua New Guinea’s Mt Tavurvur have forced some flights in and out of New Britain to be cancelled. The ash and vapor blowing from the volcano affected flights to Tokua Airport. Air Niugini says the flight suspension came into effect on Monday and will continue for an indefinite period. Newspaper reports say low to loud roaring and rumbling noises were heard on Sunday night when the volcano erupted. Tavurvur is an active volcano that lies near Rabaul in Papua New Guinea. It is a sub-vent of the Rabaul caldera and lies on the eastern rim of the larger feature. The volcano is most well known for its devastating eruptions over Rabaul. Mt Tavurvur is the most well known volcano in Rabaul caldera, and has erupted as recently as January 2009. The last time the volcano erupted was in 2011. –
December 11, 2012 – INDONESIA - A magnitude 7.3 (7.1 USGS) earthquake in the Banda Sea off Indonesia has been felt more than 600 kilometers away in Darwin. Geoscience Australia says there could be more aftershocks from the quake that shook the Top End of the Northern Territory overnight. Tremors were felt in Darwin and Katherine at about 2:30 am local time and were the strongest in the north for about 20 years. Overnight staff at the Darwin weather bureau evacuated their third-storey office while the building shook. Duty forecaster Angeline Prasad says the tremor was the strongest she has felt. “The building started shaking and it just became worse,” she said. “It is the worst tremor I’ve felt in Darwin. When things started falling off shelves we decided to go to an evacuation point, which is outside the building.” Geoscience senior seismologist Dr Mark Leonard says, while there have been quakes of a similar magnitude felt in Darwin before, people are describing last night’s tremor as particularly intense. “We have had a few reports from people saying they think it is the strongest, even though we know if you go back 20, 30 years there have been a number of earthquakes this size,” he said. “But there might have been some sort of focusing of the waves this time.” An engineering specialist says the tremor is a pointer to why building standards should be reviewed in northern Australia. Professor Kevin McKew from Central Queensland University says it is a warning that a large, damaging earthquake could strike at any time. “The big one is yet to come,” he said. “We haven’t had a great earthquake, as I would call it, but we’ve had plenty of warning calls. “I think it will happen; it’s just a matter of when will it happen. “We know it is probably a once in 300 or 400 year earthquake but we have no indication to say when it’s about to happen. But we just have to plan for it.” One Darwin resident says she was sleeping when her bed started moving. “The bed was really shaking violently, all my sliding doors rattling and windows were rattling, and the wardrobe was sliding violently and rattling,” she said. “It just seemed to go on and on and on, and then when it died down, it even had another violent shudder again. “It certainly got the adrenaline running.” Residents further south in Katherine, 200 kilometers south of Darwin, also felt tremors. Indonesian geophysics officials also said they had not received any reports of damage. The quake was felt only weakly in the districts of North Halamahera and Morotai which were closest to the epicenter, Indonesia’s National Disaster Mitigation Agency said in an update. –
April 29, 2011 – KAMCHATKA – Two of Far East Russia’s most active volcanoes threatened aviation and wildlife during eruptions that spewed ash above the Kamchatka Peninsula. Ash from Shiveluch soared nearly five miles high near some key trans-Pacific aviation routes. RIA Novosti reports an eruption of Kizimen volcano brought hazardous conditions to areas inhabited by wild animals, including some endangered species. The news agency said reindeer were leaving their normal habitat because their usual winter food supply of moss was buried beneath a thick crust of ash-covered snow. Experts from the Krontosky Nature Reserve told reporters that reindeer numbers may be reduced to less than 1,000 as a result of the eruption. -
