Fri Aug 31 2012 21:33:00 GMT+0800 (Malay Peninsula Standard Time) by BNO News
GUIUAN, PHILIPPINES (BNO NEWS) — A powerful earthquake struck off the eastern coast of the Philippines on Friday evening, prompting a tsunami warning for several countries, seismologists and officials said. It was not immediately known if it caused damage or casualties, or if a tsunami was generated.
The 7.7-magnitude earthquake at 8:47 p.m. local time (1247 GMT) was centered about 112 kilometers (69 miles) east of Guiuan, a municipality in the province of Eastern Samar in the Philippines. It struck about 10 kilometers (6.2 miles) deep, making it a shallow earthquake, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS).
The Pacific Tsunami Warning Center immediately issued a regional tsunami warning, although it was not immediately known if a destructive tsunami was generated. A tsunami warning is in effect for Indonesia, the Philippines, and the Pacific island nation of Palau, but tsunami warnings earlier issued for Yap, Taiwan, Japan, Guam, the Northern Mariana Islands, and Papua New Guinea have since been canceled.
“It is not known that a tsunami was generated. This warning is based only on the earthquake evaluation,” the Pacific Tsunami Warning Center said in a bulletin. “An earthquake of this size has the potential to generate a destructive tsunami that can strike coastlines near the epicenter within minutes and more distant coastlines within hours.”
A tsunami watch was initially also issued for islands and countries in the region, including Chuuk, the Japanese coral atoll Marcus Island, Kosrae, Pohnpei, the Marshall Islands, Wake Island, the Solomon Islands, Russia, Nauru and the U.S. state of Hawaii. They were later canceled based on new information from seismologists.
“Based on all available data there is no destructive tsunami threat to the state of Hawaii. Therefore the tsunami watch for Hawaii is canceled,” the Pacific Tsunami Warning Center said in a message to the state’s Civil Defense. “However, some coastal areas in Hawaii could experience small non-destructive sea level changes and strong or unusual currents lasting up to several hours.”
The United States Geological Survey (USGS) initially measured the strength of the earthquake at 7.9, but the magnitude was later revised down to 7.6. The agency estimated the depth of the earthquake to be approximately 39.9 kilometers (21.7 miles), making it a shallow earthquake.
USGS computer models estimated some 117,000 people living in coastal areas near the epicenter may have experienced strong shaking, which could potentially result in light to moderate damage. More than 18.5 million people may have felt light to moderate tremors, the agency said.
The Philippines is on the so-called ‘Pacific Ring of Fire’, an arc of fault lines circling the Pacific Basin which is prone to frequent and large earthquakes. Volcanic eruptions also occur frequently in the region.
In July 1990, a powerful 7.8-magnitude earthquake struck the densely populated island of Luzon, killing at least 2,412 people and injuring thousands more. It was one of the most deadliest earthquakes in the Philippines in recent history.
Only more deadly was an enormous 8.1-magnitude earthquake in August 1976 which shook Mindanao island and had its epicenter in the Moro Gulf. It caused a destructive tsunami in the Celebes Sea, causing devastation in settlements along the coast of the Moro Gulf on Mindanao island and on the nearby Sulu Islands.
The 1976 earthquake was felt on all of the central islands of the Philippines Archipelago and in the southern part of Luzon. As a result of the earthquake and tsunami, more than 8,000 people were killed or left missing, 10,000 were injured, and 90,000 were left homeless.