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Hayes G.P.,National Earthquake Information Center | Bergman E.,Global Seismological Services | Johnson K.L.,National Earthquake Information Center | Johnson K.L.,Colorado School of Mines | And 3 more authors.
Geophysical Journal International | Year: 2013

After the 2010 Mw 8.8 Maule earthquake, an international collaboration involving teams and instruments from Chile, the US, the UK, France and Germany established the International Maule Aftershock Deployment temporary network over the source region of the event to facilitate detailed, open-access studies of the aftershock sequence. Using data from the first 9-months of this deployment, we have analyzed the detailed spatial distribution of over 2500 well-recorded aftershocks. All earthquakes have been relocated using a hypocentral decomposition algorithm to study the details of and uncertainties in both their relative and absolute locations.We have computed regional moment tensor solutions for the largest of these events to produce a catalogue of 465 mechanisms, and have used all of these data to study the spatial distribution of the aftershock sequence with respect to the Chilean megathrust.We refine models of co-seismic slip distribution of the Maule earthquake, and show how small changes in fault geometries assumed in teleseismic finite fault modelling significantly improve fits to regional GPS data, implying that the accuracy of rapid teleseismic fault models can be substantially improved by consideration of existing fault geometry model databases. We interpret all of these data in an integrated seismotectonic framework for the Maule earthquake rupture and its aftershock sequence, and discuss the relationships between co-seismic rupture and aftershock distributions.While the majority of aftershocks are interplate thrust events located away from regions of maximum co-seismic slip, interesting clusters of aftershocks are identified in the lower plate at both ends of the main shock rupture, implying internal deformation of the slab in response to large slip on the plate boundary interface. We also perform Coulomb stress transfer calculations to compare aftershock locations and mechanisms to static stress changes following the Maule rupture. Without the incorporation of uncertainties in earthquake locations, just 55 per cent of aftershock nodal planes align with faults promoted towards failure by co-seismic slip. When epicentral uncertainties are considered (on the order of just ±2-3 km), 90 per cent of aftershocks are consistent with occurring along faults demonstrating positive stress transfer. These results imply large sensitivities of Coulomb stress transfer calculations to uncertainties in both earthquake locations and models of slip distributions, particularly when applied to aftershocks close to a heterogeneous fault rupture; such uncertainties should therefore be considered in similar studies used to argue for or against models of static stress triggering. © The Authors 2013. Published by Oxford University Press on behalf of The Royal Astronomical Society.


PubMed | National Earthquake Information Center, Pennsylvania State University, Natural Resources Canada, University of Chile and Global Seismological Services
Type: Journal Article | Journal: Nature | Year: 2014

The seismic gap theory identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref.2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile, which had not ruptured in a megathrust earthquake since a M8.8 event in 1877. On 1 April 2014 a M8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March-April 2014 Iquique sequence, including analyses of earthquake relocations, moment tensors, finite fault models, moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that this was not the earthquake that had been anticipated. Significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence.


News Article | January 29, 2016
Site: news.yahoo.com

Sonic booms were reported over southern New Jersey and along the East Coast to Long Island, New York, on Jan. 28, 2016. More The sonic booms that rattled residents of New Jersey up to Long Island, New York, yesterday may have been the result of fighter jet flight tests at the Naval Air Station in Patuxent River, Maryland. At 1:24 p.m. EST (18:24:05 UTC) about 2 miles (3 kilometers) north-northeast of Hammonton, New Jersey, and 37 miles (60 km) south of Trenton, New Jersey, a sonic boom was detected at nearby seismometers in the ground. At least nine others were picked up in the following hour and a half along the Eastern Seaboard up to Long Island, according to the U.S. Geological Survey (USGS). The speed of the seismic waves and other factors identified the events as sonic booms and not earthquakes, according to John Bellini, a geophysicist with the USGS National Earthquake Information Center in Golden, Colorado. When an object such as an aircraft (or an explosion) travels faster than the speed of sound (761.2 mph, or 1,225 km/h, at sea-level), the result is a shockwave that also travels faster than sound, Bellini told Live Science. [Photos: See Aircraft Breaking the Sound Barrier] Potential culprits were ruled out soon after the booms were recorded, with officials at NASA's Wallops Flight Facility on Wallops Island in Virginia confirming there weren't any rocket launches or jet flights at the center that could have caused the sonic booms. The Federal Aviation Administration and the North American Aerospace Defense Command both also confirmed no nearby planes operating that may have caused the sonic booms, as reported by ABC News yesterday. A nearby naval base was also cleared: "We have reports of ground shaking in S. Jersey-- currently our training ranges are clear and no MDL aircraft are capable of sonic booms," officials at Joint Base McGuire-Dix-Lakehurst wrote on Twitter. "We're working with local authorities to determine the cause and will have an update ASAP." But late in the afternoon, the U.S. Navy released a statement about flight testing in the area. "Aircraft from Naval Test Wing Atlantic were conducting routine flight testing in the Atlantic Test Ranges this afternoon that included activities which may have resulted in sonic booms,” the Navy said in a statement, as reported by the Washington Post. "The test wing is critical to the safe test and evaluation of all types of Navy and Marine Corps aircraft in service and in development and is primarily based out of Naval Air Station Patuxent River, Md. Other military aircraft, including both Navy and Air Force, also frequently use the ranges for testing and training." The sonic-boom culprits were likely the F-18 and the F-35C, which were the craft involved in the flight testing, according to the Washington Post. The F-18, also called the F/A-18 Hornet, is a strike fighter used as both an attack aircraft and a fighter that has a max speed of Mach 1.8, or 1.8 times the speed of sound in air. The F-35C, a Joint Strike Fighter warplane designed to operate from the flight decks of aircraft carriers, can reach speeds of Mach 1.6, according to Lockheed Martin, the defense contractor that is developing the fighter jet. "Thursday's sonic booms could well have been the result of a face-off between the F-35 and the older F-18 Hornet, a supersonic jet that the Navy has used since the mid 1980s," reported the Post. Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


News Article | January 28, 2016
Site: news.yahoo.com

Sonic booms were reported over southern New Jersey and along the East Coast to Long Island, New York, on Jan. 28, 2016. More Update: Late in the afternoon, the U.S. Navy released a statement suggesting flight testing of their fighter jets may have caused the sonic booms. Read the full story on the explanation. At least 10 sonic booms have been reported this afternoon (Jan. 28) from southern New Jersey along the East Coast to Long Island, New York, say scientists with the U.S. Geological Survey (USGS). The first sonic boom was recorded at 1:24 p.m. EST (18:24:05 UTC), about 2 miles (3 kilometers) north-northeast of Hammonton, New Jersey, and 37 miles (60 km) south of Trenton, New Jersey. In the following hour and a half, seismometers picked up at least nine other sonic booms along the Eastern Seaboard all the way to Long Island, according to the USGS. A spokesperson for the USGS said agency scientists there have no other information except that these were sonic booms and not earthquakes that were detected today. A sonic boom occurs when an object (or an explosion) travels faster than the speed of sound (761.2 mph, or 1,225 km/h, at sea-level), sending out a shockwave that also travels faster than sound, according to John Bellini, a geophysicist with the USGS National Earthquake Information Center in Golden, Colorado. [Photos: See Aircraft Breaking the Sound Barrier] The cause of today's sonic booms remains mysterious. Bellini noted, however, that if an explosion had caused these booms, someone likely would have seen it. Officials have also ruled out NASA's Wallops Flight Facility on Wallops Island in Virginia, which routinely launches small rockets and jet test flights from its Eastern Shore site. But today, no rocket launches or jet flights occurred at the NASA center, spokesman Keith Kohler said in an email. Scientists knew these were seismic waves from sonic booms and not earthquakes because of their speed. "An earthquake moves through the ground and it moves 10,000 feet per second [3,048 meters per second]," Bellini told Live Science. In today's instance, the waves were moving away from the seismometers in New Jersey at speeds that would suggest they were moving faster than sound in the air. A seismometer that tracks waves moving through the ground can pick up a sonic boom, whose waves move through the air, Bellini said. But the seismometers usually have to be pretty close to where the boom occurs, because sound doesn't transfer well into the ground. ABC News reported that the U.S. Federal Aviation Administration and the North American Aerospace Defense Command had both confirmed they didn't have any planes operating nearby that could have generated the sonic booms. No aircraft capable of sonic booms were operating at nearby naval air bases either, according to officials. "We have reports of ground shaking in S. Jersey — currently our training ranges are clear and no MDL aircraft are capable of sonic booms," officials at Joint Base McGuire-Dix-Lakehurst in Trenton, New Jersey, wrote on Twitter. "We're working with local authorities to determine the cause and will have an update ASAP." Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.


Riquelme S.,University of Chile | Fuentes M.,University of Chile | Hayes G.P.,National Earthquake Information Center | Campos J.,University of Chile
Journal of Geophysical Research B: Solid Earth | Year: 2015

Many efforts have been made to quickly estimate the maximum runup height of tsunamis associated with large earthquakes. This is a difficult task because of the time it takes to construct an accurate tsunami model using real-time data from the source. It is possible to construct a database of potential seismic sources and their corresponding tsunami a priori. However, such models are generally based on uniform slip distributions and thus oversimplify the knowledge of the earthquake source. Here we show how to predict tsunami runup from any seismic source model using an analytic solution that is specifically designed for subduction zones with a well-defined geometry, i.e., Chile, Japan, Nicaragua, and Alaska. The main idea of this work is to provide a tool for emergency response, trading off accuracy for speed. The solutions we present for large earthquakes appear promising. Here runup models are computed for the following: the 1992 Mw 7.7 Nicaragua earthquake, the 2001 Mw 8.4 Perú earthquake, the 2003 Mw 8.3 Hokkaido earthquake, the 2007 Mw 8.1 Perú earthquake, the 2010 Mw 8.8 Maule earthquake, the 2011 Mw 9.0 Tohoku earthquake, and the recent 2014 Mw 8.2 Iquique earthquake. The maximum runup estimations are consistent with measurements made inland after each event, with a peak of 9 m for Nicaragua, 8 m for Perú (2001), 32 m for Maule, 41 m for Tohoku, and 4.1 m for Iquique. Considering recent advances made in the analysis of real-time GPS data and the ability to rapidly resolve the finiteness of a large earthquake close to existing GPS networks, it will be possible in the near future to perform these calculations within the first minutes after the occurrence of similar events. Thus, such calculations will provide faster runup information than is available from existing uniform-slip seismic source databases or past events of premodeled seismic sources. ©2015. The Authors.


Wei Y.,University of Washington | Wei Y.,U.S. National Center for Atmospheric Research | Titov V.V.,U.S. National Center for Atmospheric Research | Newman A.,Georgia Institute of Technology | And 5 more authors.
OCEANS'11 - MTS/IEEE Kona, Program Book | Year: 2011

Tsunami source is the origin of the subsequent transoceanic water waves, and thus the most critical component in modern tsunami forecast methodology. Although impractical to be quantified directly, a tsunami source can be estimated by different methods based on a variety of measurements provided by deep-ocean tsunameters, seismometers, GPS, and other advanced instruments, some in real time, some in post real-time. Here we assess these different sources of the devastating March 11, 2011 Japan tsunami by model-data comparison for generation, propagation and inundation in the near field of Japan. This study provides a comparative study to further understand the advantages and shortcomings of different methods that may be potentially used in real-time warning and forecast of tsunami hazards, especially in the near field. The model study also highlights the critical role of deep-ocean tsunami measurements for high-quality tsunami forecast, and its combination with land GPS measurements may lead to better understanding of both the earthquake mechanisms and tsunami generation process. © 2011 MTS.


News Article | January 4, 2016
Site: news.yahoo.com

A magnitude-6.7 earthquake shook Manipur state in India Sunday (Jan. 3), collapsing buildings and causing at least 10 deaths, according to news reports. The quake hit at 4:35 a.m. local time, 18 miles (29 kilometers) from the city of Imphal, in an area where large temblors are common. These quakes occur because of the collision of the India and Eurasia tectonic plates, which are converging at a rate of about 2 inches (5 centimeters) per year, according to the U.S. Geological Survey (USGS). The geology of the area is particularly complex, said Harley Benz, the scientist-in-charge at the USGS National Earthquake Information Center in Golden, Colorado. "This is not the case of something like the San Andreas, where you have a well-defined fault and it's shallow and it has a relatively small width to it," Benz told Live Science. "This is in the mantle, where you have a broad area of deformation." [Photo Journal: The Gorgeous San Andreas Fault] The towering peaks of the Himalayas and the Hindu Kush, among other mountains, testify to the tectonic forces underlying the meeting point of the India and Eurasian plates. This is the 20th quake of magnitude-6 or greater to hit within 155 miles (250 kilometers) of the epicenter of Sunday's Manipur quake in the past century, according to the USGS. "We know that this area is seismically active, and so having an earthquake of this size is not unusual," Benz said. According to the agency, the Manipur quake originated on a strike-slip fault. These are faults that run vertically, with the blocks of crust on either side moving horizontally in relation to one another. (You can see an animation of a strike-slip fault on the USGS website.) The region where the quake struck is in a transitional zone, Benz said. To the south, near Sumatra and the Andaman Islands, the India plate is slipping under the Eurasian plate in a straightforward example of subduction. This results in some strike-slip quakes, but more thrust-fault temblors, which push old rock layers over new ones at a low angle. North of the Manipur region, along the Himalayan front, the majority of earthquakes are likewise along shallow thrust faults, Benz said. One example is the magnitude-7.8 quake that hit Nepal in April 2015. That quake killed more than 9,000 people, destroyed historic buildings and moved Mount Everest an inch. In between those two regions sits the transitional zone where the latest quake hit and where the geology is quite complicated, Benz said. Deeper quakes like the Manipur temblor, which had a depth of about 34 miles (55 km), tend to cause less surface damage than those that originate higher up, in the crust, Benz said. "Had it been a shallow earthquake, as close as it was to the town, it could have caused a lot more damage," he said. Imphal sits in a basin, however, which could have locally amplified the quake's waves, explaining some of the damage. Local officials told news agencies today (Jan. 4) that the quake had killed at least 10 people and injured more than 100. "You end up getting a higher duration of ground shaking [locally], because the waves get in the basin and they tend to rattle around," Benz said. Reports on the USGS website indicate that the Manipur quake was felt as far away as Kathmandu, which was affected by the much larger magnitude-7.8 quake last April. The USGS has not detected any significant aftershocks from the Manipur quake — a fact that could be attributed to the quake's depth, Benz said. "Typically, when you go deeper into the mantle, the number of aftershocks you might have drops off significantly compared to [those seen with] crustal earthquakes," Benz said. Follow Stephanie Pappas on Twitter and Google+. Follow us @livescience, Facebook & Google+. Original article on Live Science. Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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