Acehtsunami

The following is a release by the United States Geological Survey, National Earthquake Information Center: An earthquake occurred 225 km (140 miles) ESE of Visokoi Island, South Sandwich Islands at 8:57 AM MST, Feb 23, 2008 (1:57 PM local time in South Sandwich Is.). The magnitude and location may be revised when additional data and further analysis results are available. There have been no reports of damage. The magnitude was furnished by the G.S. Depth 10 km (6.2 miles) set by location program.

A major earthquake with a moment magnitude of 7.3 (USGS magnitude) occurred at 124613 UTC 9 April 2008 (day 100) and was located 70 km SW of Isangel, Tanna, Vanuatu (20.058�S, 168.858�E, 35 km depth - USGS location).

The earthquake produced a tsunami that was recorded at the Port Vila, Vanuatu tide gage monitored at the Tsunami Warning Centers. The data was provided by the National Tidal Facility in Australia. Click on the site name to see a graph of the tsunami. Listed wave heights are maximum amplitude in cm (above sea level). Observed Arrival time is the actual tsunami arrival time in UTC on gages where it could be determined. The Computed Arrival time is the estimated time of arrival computed at the West Coast/Alaska Tsunami Warning Center (WC/ATWC) based on the origin time and location. The Sample Interval column shows the time between samples.

The following is a release by the United States Geological Survey, National Earthquake Information Center: An earthquake occurred 15 km (10 miles) ESE of Wells, Nevada 15 km (10 miles) ESE of Wells, Nevada at 7:16 AM MST, Feb 21, 2008 (6:16 AM PST in Nevada). The magnitude and location may be revised when additional data and further analysis results are available.

Felt Reports

At least three people injured and over twenty buildings heavily damaged and almost seven hundred buildings slightly damaged (VI) at Wells, Nevada. Felt (V) at Jackpot; (IV) at Battle Mountain, Carlin, Elko, Mountain City and Spring Creek; (III) at Ely, Eureka, Golconda, Lovelock and Winnemucca; (II) at Fallon and Reno, Nevada; (V) at Grand View and Rogerson; (IV) at Castleford, Filer, Hansen, Heyburn, Malad City, Malta, Paul, Rupert, Twin Falls and Wendell, (III) at American Falls, Bellevue, Boise, Buhl, Burley, Caldwell, Declo, Dietrich, Emmett, Fairfield, Garden Valley, Glenns Ferry, Gooding, Hagerman, Hailey, Hazelton, Idaho City, Inkom, Jerome, Ketchum, Kimberly, Middleton, Murtaugh, Nampa, Pocatello and Shoshone, (II) at Eagle, Garden City, Idaho Falls, Kellogg, Kuna, Lava Hot Springs, Mccammon, Meridian, Mountain Home, Preston and Star, Idaho; (V) at Wendover, (IV) at Farmington, Garland Salt Lake City and Snowville, (III) at American Fork, Brigham City, Clearfield, Corinne, Draper, Dugway, Grantsville, Hill AFB, Honeyville, Hooper, Hyde Park, Hyrum, Layton, Lehi, Logan, Ogden, Plymouth, Provo, Richmond, Roy, Sandy, Stockton, Syracuse, Tooele, Tremonton and West Jordan, (II) at Alpine, Bountiful, Delta, Kaysville, Lewiston, Magna, Midvale, North Salt Lake, Orem, Park City, Pleasant Grove, Providence, Riverton, Smithfield, South Jordan, Wellsville and Woods Cross, Utah; (II) at Spokane, Washington. Also felt at Laveen, Phoenix and Tucson, Arizona; Carmel Valley, Citrus Heights, Fort Bragg, Fresno, Huntington Beach, Midway City, Modesto, Newcastle, Oakland, Orange, Pasadena, Redwood City, Rocklin, Sacramento, San Ramon, Stockton and Ontario, California; Brighton and Fruita, Colorado; Aberdeen, Arco, Arimo, Bliss, Eden, Fish Haven, Greenleaf, Hammett, Homedale, Howe, Idaho Falls, Letha, Lucile, Mccall, Montpelier, Mountain Home A F B, Mullan, Murphy, New Plymouth, Paris, Parma, Pinehurst, Rockland, Soda Springs, Weiser, Weston and Wilder, Idaho; Absarokee, Montana; Albuquerque, New Mexico; Baker, Crescent Valley, Deeth, Denio, Fernley, Henderson, Nellis AFB, Overton, Pioche, Round Mountain, Tonopah and Yerington, Nevada; Burns, Harper, Jordan Valley, Nyssa and Ontario, Oregon; Bingham Canyon, Cedar Valley, Centerville, Clarkston, Cornish, Dutch John, Eden, Fielding, Grouse Creek, Hinckley, Huntsville, Lindon, Mendon, Mona, Morgan, Orem, Park, City, Payson, Portage, Rush Valley, Salem, Spanish Fork, Springville, Talmage, Vernon, Willard, Utah; Afton and Rock Springs, Wyoming.

Tectonic Summary

Seismological data from this earthquake show that it occurred on a normal fault that trends roughly north-south and has a dip of 30-60 degrees. The revised location of the mainshock puts the earthquake in the area northeast of Wells, Nevada, where geologically young faulting is poorly expressed. The USGS Quaternary Faults and Folds Database describes a network of widely distributed faults west of Wells Peak. Based on the revised location, the distribution of several aftershocks, and the depth of the mainshock, it is difficult to associate the earthquake with a specific fault.

A significant fault in the region that shows evidence of geologically young movement is the 64-km-long Independence Valley fault zone, which bounds the western side of the Pequop Mountains, but it is located more than 20 km southeast of the revised epicentral location and was probably not the source of the earthquake.

Earthquakes in Nevada are not uncommon. One of the most significant sequences of earthquakes in the western U.S. occurred in Nevada during the first half of the 20th century. The sequence started in 1915, when a magnitude 7.1 earthquake occurred in Pleasant Valley south of Winnemucca. The sequence culminated with a series of four major earthquakes that ranged in magnitude between 6.6 to 7.1 in 1954 the vicinity of the Carson Sink and Dixie Valley. This sequence of earthquakes defines the Central Nevada Seismic Belt.

A major earthquake with a moment magnitude of 7.8 (USGS magnitude) occurred at 0728 UTC 12 December 2007 (day 349) and was located south of the Fiji Islands (25.872�S, 177.517�W, 149.2 km depth - USGS location).

The earthquake produced a tsunami that was recorded at the Kings Wharf, Fiji tide gage monitored at the Tsunami Warning Centers. The data was provided by the National Tidal Facility in Australia. Click on the site name to see a graph of the tsunami. Listed wave heights are maximum amplitude in cm (above sea level). Observed Arrival time is the actual tsunami arrival time in UTC on gages where it could be determined. The Computed Arrival time is the estimated time of arrival computed at the West Coast/Alaska Tsunami Warning Center (WC/ATWC) based on the origin time and location. The Sample Interval column shows the time between samples.

The following is a release by the United States Geological Survey, National Earthquake Information Center: An earthquake occurred 310 km (195 miles) SSE of Banda Aceh, Sumatra, Indonesia, 310 km (195 miles) WSW of Medan, Sumatra, Indonesia, 335 km (210 miles) WNW of Sibolga, Sumatra, Indonesia, 1545 km (960 miles) NW of JAKARTA, Java, Indonesia at 1:08 AM MST, Feb 20, 2008 (3:08 PM local time in Indonesia). The magnitude and location may be revised when additional data and further analysis results are available. Earthquakes of this type sometimes cause tsunamis, however the USGS has no information that an actual tsunami has been generated.

Felt Reports

Three people killed and 25 seriously injured in the western Aceh province. Felt (V) at Meulaboh; (IV) at Banda Aceh, Medan and Tapaktuan; (III) at Gunungsitoli, Padang and Sibolga; (II) at Payakumbuh and Bukittinggi. Also felt at Duri and Lhokseumawe. Felt (III) at Butterworth, Gelugor, George Town, Kuala Lumpur, Petaling Jaya, Sungai Ara and Tanjong Tokong and (II) at Perai. Also felt at Alor Setar, Ayer Itam, Juru, Kajang-Sungai Chua, Kampong Tanjong Bunga, Kampong Tanjung Karang, Klang, Kota Baharu, Kuah, Kulim, Nibung Tepal and Shah Alam, Malaysia. Also felt at Kathu, Thailand.

Tectonic Summary

The magnitude 7.4 Simeulue, Indonesia earthquake of February 20, 2008 occurred as the result of thrust faulting on the boundary between the Australia and Sunda plates. At the location of this earthquake, the Australia plate moves north-northeast with respect to the Sunda plate at a velocity of about 55 mm/year. The direction of relative plate motion is oblique to the orientation of the plate boundary offshore of the west coast of Sumatra. The component of plate-motion perpendicular to the boundary is accommodated by thrust faulting on the offshore plate-boundary, with the Australia plate subducting beneath the Sunda plate. Much of the component of plate motion parallel to the plate boundary is accommodated by strike-skip faulting on the Sumatra fault, which is inland on Sumatra proper.

This earthquake occurred at the south end of the rupture zone of the great magnitude 9.1 earthquake of December 26, 2004 and at the north end of the rupture zone of the magnitude 8.6 Nias Island earthquake of March 28, 2005, where the 2004 and 2005 rupture zones nearly abut. The earthquake of December 26, 2004, produced the devastating Indian Ocean tsunami of that date. Since 2000, much of the Sunda trench between the northern Andaman Islands to Eggano Island, a distance of more than 2,000 km, has ruptured in a series of large subduction zone earthquakes.

A large earthquake with a moment magnitude of 7.7 (USGS magnitude) occurred at 1541 UTC 14 November 2007 (day 318).� The earthquake was located 25 miles/40 km ESE of Tocopilla, Chile (22.2�S, 69.8�W, 25 miles/40 km depth – USGS location).

The earthquake produced a tsunami that was recorded at tide gages monitored at the Tsunami Warning Centers (the tide sites are operated by the Chilean Navy and the National Ocean Service). Click on the site name to see a graph of the tsunami. Listed wave heights are maximum amplitude in cm (above sea level). Observed Arrival time is the actual tsunami arrival time in UTC on gages where it could be determined. The Computed Arrival time is the estimated time of arrival computed at the West Coast/Alaska Tsunami Warning Center (WC/ATWC) based on the origin time and location. The Sample Interval column shows the time between samples.