mitigating risk in the 2004 denali fault earthquake

On average, Alaska has had one M 8+ earthquake every 13 years, one M 7-8 earthquake every two years, and six M 6-7 earthquakes per year (Alaska Seismic Hazards Safety Commission, 2012). Dr. Jeff Freymueller of the Geophysical Institute, University of Alaska Fairbanks, has been measuring the motion and deformation of the Earth near the Denali Fault by repeating measurements of the position of a survey marker in the ground over a period of years. We map the 385-kilometer (km) long surface trace of the right-lateral, strike-slip Denali Fault between the Totschunda-Denali Fault intersection in Alaska, United States and the village of Haines Junction, Yukon, Canada. The AEIC located over 1,000 aftershocks of the M 6.7 event prior to the M 7.9 mainshock and over 35,000 aftershocks through the end of 2004. The 2002 M7.9 Denali fault earthquake resulted in 340 km of ruptures along three separate faults, causing widespread liquefaction in the fluvial deposits of the alpine valleys of the Alaska Range and eastern lowlands of the Tanana River. Earthquakes shake the ground daily, but most are minor local events. The basic structure of methods for estimating hazard was developed by engineers needing quantitative answers despite the wide range of uncertainties ( 1 ). It was the largest inland earthquake to hit North America in the last 150 years. Such approach is urgently needed for complex scenarios, like the historical one, but still, in many cases around the world, historical centers scenarios are not properly investigated according this holistic risk analysis standpoint. To understand the risk that different areas of the U.S. face for earthquake hazards, we need to know where faults are and how they behave. Although people tend to view the Earth as static and stable between earthquakes, every point is actually moving slowly as Earth’s tectonic plates move around. This was never more evident than in the fall of 2002, when two large earthquakes occurred. The largest surface offsets of 8.8 meters (29 feet) were observed farther to the east. The pipeline crosses the Denali fault some 90 miles south of Fairbanks. Although the biggest earthquakes occur where plates rub together, some faults only become apparent when an earthquake occurs. Similarly, the largest recorded earthquake in North American history also occurred on a subduction zone fault … Mitigating earthquake risk in Australia M.R. We map the 385-kilometer (km) long surface trace of the right-lateral, strike-slip Denali Fault between the Totschunda-Denali Fault intersection in Alaska, United States and the village of Haines Junction, Yukon, Canada. Such knowledge is needed to predict ground motions in future earthquakes so that earthquake-resistant structures can be designed. Remove maintenance message and minor earthquakes on the subduction zone in a cluster pattern. AEIC analysts locate between 20,000 and 30,000 earthquakes in Alaska each year. The section of the Denali fault cutting across the park has not experienced a major earthquake within the last ~100 years. Alaska’s Denali Fault was on the move, jostling the state with a magnitude 7.9 earthquake. The fault's rate of displacement varies from 1 mm to 35 mm per year. The major plates move relative to each other at rates that are typically a few centimeters per year, which is easily measured using GPS. Great earthquakes (those with M greater than 8.0) typically occur along the Pacific-North American plate boundary far south of the park. Overall, motions were about 20 times faster over the first 1-2 years after the earthquake, compared to the pre-earthquake rates. Earthquake hazards Ground Rupture Alaskan pipe after the Denali quake ruptured through Ground rupture from the M8.1 2001 Tibet earthquake Earthquake hazards (cont.) The Pacific plate is moving northwest relative to Alaska, causing many earthquakes along the interface. AEIC has four seismic stations in Denali: (from west to east, see map) Castle Rocks (CAST), Kantishna Hills (KTH) on Wickersham Dome, Thoroughfare Mountain (TRF), and McKinley (MCK) near the park entrance. Geoscientists are able to identify particular areas of risk and, if there is sufficient information, to make probabilistic forecasts about the likelihood of earthquakes happening in a specified area over a specified period. The 2002 M7.9 Denali fault earthquake resulted in 340 km of ruptures along three separate faults, causing widespread liquefaction in the fluvial deposits of the alpine valleys of the Alaska Range and eastern lowlands of the Tanana River. In the Aleutian Islands, where the subduction angle is much steeper, the shallow-todeep earthquake pattern is more compact. Fortunately, no one was seriously injured, due to the small population located The Kantishna cluster is a group of small, shallow earthquakes—not far from Wonder Lake—at the southwestern end of a shear zone. The cause? The red line represents the fault, which runs east toward Mt. The 7.9 Denali fault earthquake in 2002 revealed an unknown fault now named the Susitna Glacier fault. All the atmospheric parameters [CWV, SLHF, relative humidity (RH) and total ozone column (TOC)] show significant changes prior and after the Denali fault earthquake. The earthquake caused an offset of nearly 6 meters (20 feet) where it crossed … Postseismic deformation results from different physical processes, including continued slip on the fault plane or its deeper extension and viscous flow in the Earth’s mantle. The November 2002 earthquake had a magnitude of 7.9 and caused a surface rupture 325 km (~200 miles) long, mostly on the central Denali Fault (see red line on map below). The 2002 Denali EQ, the Trans-Alaska Oil Pipeline and EQ Hazard Mitigation On Nov 3, 2002 a large magnitude 7.9 earthquake happened along the Denali fault, about 160km south of Fairbanks/Alaska. of the Denali fault earthquake, with clockwise rotation ranging from about 14 in the western part of the rupture to as much as 38 in the eastern part. During the afternoon of November 3, 2002, the water in Seattle’s Lake Union suddenly began sloshing hard enough to knock houseboats off their moorings. 94, no. Most people in Interior Alaska were reminded of the fault’s earthquake potential when it ruptured on November 3, 2002. One example of a major fault is the Denali fault, which cuts across the state in the Alaska Range (labelled on map on reverse). In the months that followed, roughly 25,000 aftershocks were located on the Denali and Totshunda faults, revealing a surface rupture that was 325 km (200 miles) long. Understanding the risk and getting ready for a large earthquake on the Hayward Fault like the one depicted in this scenario can help other at-risk communities prepare for similar events that are possible in their area. The earthquake lasted about 100 seconds. These quakes are associated with the northern extension of the subduction edge of the Pacific plate and its dive beneath the North American crust. Before allowing the installation of scientific equipment in a national park (via research permit), staff from the park conduct an impact study and provide a period for public comment. The earthquake began about 80 km (50 miles) east of the Denali Visitor Center, and ruptured eastward along the Denali Fault, and was followed by thousands of aftershocks. As the stress mounts along the Denali fault in the park, and as more time elapses without the stress release of a strong earthquake, the probability of a big earthquake in the park continues to rise. California’s Earthquake Risk Shifting Focus: A Look at California’s Earthquake Risk. earthquake, which would result in a maximum PGA of 0.17g at Pebble. Larger earthquakes tend to shake longer and harder and therefore cause more damage to structures1. The Denali fault earthquake (Mw = 7.9) of November 3, 2002 was the largest strike–slip earthquake (Eberhart-Phillips et al., 2003) that occurred in North America in almost 150 years. This presents a rare opportunity to catch a major earthquake in the act. Water in pools, ponds, and bayous as far away as Texas and Louisiana splashed for nearly half an hour. Every event is briefly reviewed by the on-duty seismologist, and carefully relocated by an analyst. Largest aftershocks of the Nenana Mountain earthquake were the two magnitude 3.8 events. In phases, three models On October 23, people of Interior Alaska were awakened to strong shaking caused by a magnitude 6.7 earthquake. earthquake, which would result in a maximum PGA of 0.17g at Pebble. The 1964 Good Friday Earthquake is an example. Areas affected by liquefaction are largely confined to Holocene alluvial deposits, man-made embankments, and backfills. A major earthquake along the fault could cause the pipeline to rupture, spilling crude oil into the surrounding environment. Real time ground motion data from ~400 seismic stations across the state are used to identify and characterize each earthquake in Alaska. 2 San Andreas ... Denali fault, Alaska Magnitude 7.9 2002 ... 2004 2010 2011. Seismicity in interior Alaska north of the Denali fault is dominated by shallow events (see blue dots on map above). Mitigation underground fault. About Cookies, including instructions on how to turn off cookies if you wish to do so. McKinley) that dominates the park landscape. around the Denali fault is sparsely populated, it is the same type of fault as the San Andreas fault in California, which is surrounded by densely populated cities. Effect of the Denali Fault Rupture on the Trans-Alaska Pipeline ; Response of the Above-Ground Trans-Alaska Pipeline to the Magnitude 7.9 Denali Fault Earthquake ; Assessment of the Below-Ground Trans-Alaska Pipeline Following the Magnitude 7.9 Denali Fault Earthquake High precision Global Positioning System (GPS) surveying can now measure positions of survey points with a precision of a few millimeters. The section of the fault in the park is just as active as the section to the east, and at some point in the future it will also break in a large earthquake. Major earthquakes (those with a magnitude range of 7.0-7.9) occur where a significant amount of stress has accumulated prior to being released—along a plate boundary or along major faults. The earthquake caused an offset of nearly 6 meters (20 feet) where it crossed the Richardson Highway and Trans-Alaska Pipeline. Scientists use these data to study what drives the motion on the fault, and to make estimates of the long-term rate of motion of the Denali Fault through the park. Between these In 2002, the M 7.9 earthquake ruptured a portion of the Denali fault east of the park to produce a horizontal offset of up to 8.8 m (29 feet). The epicenters (point on the earth surface where the quakes originate) of each of these large earthquakes was about 50 km (30 miles) east of the park, on the Denali fault. S58–S71, 2004. Combined with geological investigations of past earthquake ruptures on this section of the fault, these studies will allow a better assessment of the earthquake hazards posed by this significant fault. Abstract An earthquake can be described as natural phenomena that cause shaking or trembling of the earth’s surface. It was evident, during damage assessment evaluations after the Denali fault event, that the residents of the smaller at-risk communities had little understanding of the earthquake hazard, had not implemented measures to mitigate damage, and were unprepared to respond to the consequences of damage. However, the duration of shaking associated with a magnitude 9.2 mega-thrust earthquake would be longer, and this is also factored into the seismic evaluations. Alaska is the most geologically active part of the United States. Denali National Park is located very close to the Denali fault. The Denali Fault has a lower seismic risk, with a maximum Geoscientists are able to identify particular areas of risk and, if there is sufficient information, to make probabilistic forecasts about the likelihood of earthquakes happening in a specified area over a specified period. A real earthquake on the Hayward Fault could occur at any time and with a different pattern of shaking. The M W (moment magnitude) 7.9 Denali fault earthquake on 3 November 2002 was associated with 340 kilometers of surface rupture and was the largest strike-slip earthquake in North America in almost 150 years. If the automatic location algorithms indicate a large earthquake, the seismologist on duty responds immediately (seismologists are on call 24/7) and issues an information release—in part to help emergency management personnel respond to significant events. Denali fault earthquake to evaluate structural damage in that event. Note how the blue dots scattered at the top of the map track roughly northeast-trending parallel lines. The focus of our investigation was to characterize the spatial extent and amplitude of ground failures and fault displacements, and assess damage to structures. Following the Denali Fault earthquake, adjacent fault segments have been stressed, increasing the likelihood of additional earthquakes on those segments. 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