Geological Survey Earthquake Research Articles

Classifying Seismic Events Linked to Solar Activity: A Retrospective LSTM Approach Using Proton Density

The influence of solar activity on seismic activity is a subject of debate. Previous studies have shown that there is sometimes a correlation and sometimes a contradiction between solar activity maxima and large earthquakes. Long-term memory neural network is used to study the relationship between solar activity and seismic activity. This study emphasizes retrospective classification rather than direct prediction, refining the LSTM architecture to maximize classification accuracy and processing data from the Solar and Heliospheric Observatory and the U.S. Geological Survey earthquake catalogs. A declustering technique is used to select large seismic events and weighted learning corrects for class imbalances. The LSTM model accurately classified earthquakes (84.47%) and proton density variations. The results support the theory that solar activity, in particular proton density, can anticipate earthquake events.

Seismoacoustic Signatures Observed During a Long-Term Deployment of Infrasound Sensors at the Nevada National Security Site

ABSTRACT Earthquakes have repeatedly been shown to produce inaudible acoustic signals (<20 Hz), otherwise known as infrasound. These signals can propagate hundreds to thousands of kilometers and still be detected by ground-based infrasound arrays depending on the source strength, distance between source and receiver, and atmospheric conditions. Another type of signal arrival at infrasound arrays is the seismic induced motion of the sensor itself, or ground-motion-induced sensor noise. Measured acoustic and seismic waves produced by earthquakes can provide insight into properties of the earthquake such as magnitude, depth, and focal mechanism, as well as information about the local lithology and atmospheric conditions. Large earthquakes that produce strong acoustic signals detected at distances greater than 100 km are the most commonly studied; however, more recent studies have found that smaller magnitude earthquakes (Mw<2.0) can be detected at short ranges. In that vein, this study will investigate the ability for a long-term deployment of infrasound sensors (deployed as part of the Source Physics Experiments [SPE] from 2014 to 2020) to detect both seismic and infrasonic signals from earthquakes at local ranges (<50 km). Methods used include a combination of spectral analysis and automated array processing, supported by U.S. Geological Survey earthquake bulletins. This investigation revealed no clear acoustic detections for short range earthquakes. However, secondary infrasound from an Mw 7.1 earthquake over 200 km away was detected. Important insights were also made regarding the performance of the SPE networks including detections of other acoustic sources such as bolides and rocket launches. Finally, evaluation of the infrasound arrays is performed to provide insight into optimal deployments for targeting earthquake infrasound.

Geomorphology, Three-Dimensional Geology, and Seismologic Hazards of the New Madrid Seismic Zone in Dyer County, Tennessee

ABSTRACTGeomorphic and three-dimensional geologic mapping reveals two major fault systems of the seismically active Reelfoot rift pass beneath Dyer County in northwestern Tennessee, the Reelfoot South fault, and the east-bounding faults of the Reelfoot rift. The Dyer County mapping also indicates that the two principal Reelfoot South fault hanging wall structures, the Lake County uplift and Tiptonville dome, pass beneath the county. Quaternary displacement was identified on southeastern Reelfoot rift margin faults in Dyer County, thus indicating that this rift margin has been active during the Quaternary from adjacent Obion County through Dyer County to Lauderdale County, Tennessee, for a distance of at least 60 km. The three-dimensional geologic mapping also provides stratigraphic thicknesses of surface sediment and underlying Paleogene and Cretaceous strata that significantly contribute to the estimation of ground motion in the event of a future large New Madrid seismic zone earthquake. The new ground motion maps using the three-dimensional geology of Dyer County are compared to the current U.S. Geological Survey earthquake hazard maps. This comparison reveals generally lower acceleration for buildings less than four stories high and greater acceleration for buildings greater than 10 stories high in the event of a large New Madrid seismic zone earthquake.

Now Trending … Earthquake Information

Abstract The U.S. Geological Survey Earthquake Hazards Program has overall successfully fulfilled its mission of providing timely earthquake information via web applications and other methods. Imagine a single month of earthquake data delivery, serving 3.6 billion total data requests, including 29 million pageviews by 7.1 million users, 606 million automated data feeds, and 45 million catalog downloads. Yet, some challenges and lapses in delivery have happened at critical times, including during the Ridgecrest earthquakes in 2019. We delve into the evolving demand for real-time information as well as the technologies put in place to support the ever-growing number of users in an increasingly mobile world.

Orthogonal Fault Rupture and Rapid Postseismic Deformation Following 2019 Ridgecrest, California, Earthquake Sequence Revealed From Geodetic Observations

AbstractWe studied the 2019 Mw6.4 and Mw7.1 Ridgecrest, California, earthquake sequence, using Sentinel‐1 and ALOS‐2 coseismic interferograms and subpixel offsets to retrieve the three‐dimensional (3‐D) surface displacements. By inverting the 3‐D displacements, optimal dip angles of the earthquake faults and the slip model were obtained. The interferometric synthetic aperture radar‐based slip model supplemented with the analysis of GPS data shows that the Mw6.4 event ruptured two orthogonal faults and its major geodetic moment was released by sinistral motion on a NE‐SW trending fault that dips 78° NW. Right‐lateral slip on NW‐SE trending subvertical faults was responsible for the Mw7.1 earthquake. Postseismic analysis with U.S. Geological Survey earthquake catalog and GPS time series at site P595 shows that the postseismic surface deformation following the Mw7.1 event has similar temporal patterns with the postseismic moment release, but requires more energy. This implies that the early aftershocks were likely controlled by rapid afterslip following the mainshock.

Who Participates in the Great ShakeOut? Why Audience Segmentation Is the Future of Disaster Preparedness Campaigns.

Background: In 2008, the Southern California Earthquake Center in collaboration with the U.S. Geological Survey Earthquake Hazards Program launched the first annual Great ShakeOut, the largest earthquake preparedness drill in the history of the United States. Materials and Methods: We collected online survey data from 2052 campaign registrants to assess how people participated, whether audience segments shared behavioral patterns, and whether these segments were associated with five social cognitive factors targeted by the ShakeOut campaign. Results: Participants clustered into four behavioral patterns. The Minimal cluster had low participation in all activities (range: 0–39% participation). The Basic Drill cluster only participated in the drop, cover and hold drill (100% participation). The Community-Oriented cluster, involved in the drill (100%) and other interpersonal activities including attending disaster planning meetings (74%), was positively associated with interpersonal communication (β = 0.169), self-efficacy (β = 0.118), outcome efficacy (β = 0.110), and knowledge about disaster preparedness (β = 0.151). The Interactive and Games cluster, which participated in the drill (79%) and two online earthquake preparedness games (53% and 75%), was positively associated with all five social cognitive factors studied. Conclusions: Our results support audience segmentation approaches to engaging the public, which address the strengths and weaknesses of different segments. Offering games may help “gamers” gain competencies required to prepare for disasters. Targeting the highly active Community-Oriented cluster for leadership roles could help build community resilience by encouraging others to become more involved in disaster planning. We propose that the days of single, national education campaigns without local variation should end.

Global Positioning System Data Collection, Processing, and Analysis Conducted by the U.S. Geological Survey Earthquake Hazards Program

ABSTRACT The U.S. Geological Survey Earthquake Science Center collects and processes Global Positioning System (GPS) data throughout the western United States to measure crustal deformation related to earthquakes and tectonic processes as part of a long‐term program of research and monitoring. Here, we outline data collection procedures and present the GPS dataset built through repeated temporary deployments since 1992. This dataset consists of observations at ∼1950 locations. In addition, this article details our data processing and analysis procedures, which consist of the following. We process the raw data collected through temporary deployments, in addition to data from continuously operating western U.S. GPS stations operated by multiple agencies, using the GIPSY software package to obtain position time series. Subsequently, we align the positions to a common reference frame, determine the optimal parameters for a temporally correlated noise model, and apply this noise model when carrying out time‐series analysis to derive deformation measures, including constant interseismic velocities, coseismic offsets, and transient postseismic motion.

Detection Threshold and Location Resolution of the Alberta Geological Survey Earthquake Catalogue

The Western Canada Sedimentary Basin (WCSB) is a low seismicity area, with fewer than fifteen cataloged M L>3.5 events since 1985 (Earthquakes Canada, 2013b). Since 1918, there have been more than 800 earthquakes reported in this region (Earthquakes Canada, 2013b), mainly clustered near the town of Rocky Mountain House (Rebollar et al. , 1982, 1984; Wetmiller, 1986), the Brazeau River (Schultz et al. , 2014), Fort St. John (Horner et al. , 1994), Turner Valley, Kinbasket Lake (Ellis and Chandra, 1981), and the Horn River Basin (BC Oil and Gas Commission, 2012); a single event larger than M L 4.5 was also reported near Snipe Lake (8 March 1970, 18:52:18 UTC; see Milne, 1970). The most active of these clusters is in the Strachan D‐3A gas field near Rocky Mountain House, where 146 events were recorded over a span of 23 days in 1980 (Wetmiller, 1986). Many of these aforementioned clusters have been conjectured as induced by gas extraction (Baranova et al. , 1999), waste water disposal (Horner et al. , 1994; Schultz et al. , 2014), or hydraulic fracturing operations (BC Oil and Gas Commission, 2012; Farahbod et al. , 2014). Historically, the compilation of the Earthquakes Canada Catalogue (EqCC) has been the responsibility of Natural Resources Canada (NRCan). More recently, a new initiative was taken by the Alberta Geological Survey (AGS) to improve the earthquake catalog in an effort to better understand the tectonics and seismicity of Alberta (AB). Interested readers are referred to Stern et al. (2013) for specific details on the methodology, station parameters, and earthquake locations of the AGS catalog. Overall, the quality and density of documented earthquakes is subject to the performance of the recording array (Fig. 1). Similar to the EqCC, the AGS catalog includes continuous waveform data from the Canadian National Seismic Network (CNSN); …

Real-Time Assessment of the Broadband Coseismic Deformation of the 2011 Tohoku-Oki Earthquake Using an Adaptive Kalman Filter

Online Material: Matlab scripts and example data for adaptive Kalman filter. The 2011 M w 9.0 Tohoku‐Oki earthquake was the most disastrous known event in Japan,triggering a powerful tsunami wave with a maximum amplitude of ∼40 m (Mori et al. , 2012). At least 15,883 people were killed and over 6145 injured, with a total economic loss of more than $235 billion U.S., making it the costliest natural disaster in world history (Emergency Disaster Countermeasures Headquarters, 2011; Hennessy‐Fiske, 2011). The earthquake occurred at 14:46:24 Japan Standard Time (05:46:24 UTC), with epicenter location at 38.297° N, 142.372° E and depth of 30 km (U.S. Geological Survey Earthquake Hazards Program, 2011). Seismic waveforms were recorded by continuous Global Navigation Satellite Systems (GNSS) monitoring network of GNSS Earth Observation Network (GEONET) (Sagiya et al. , 2001) and strong‐motion seismograph networks of the Kyoshin Network (K‐NET) and Kiban Kyoshin Network (KiK‐net) (Aoi et al. , 2004). These have been separately or jointly applied to rapid earthquake magnitude determination (Ohta et al. , 2012; Wright et al. , 2012; Melgar, Crowell, et al. , 2013), tsunami warning (Melgar and Bock, 2013), earthquake rupture process inversion (Ide et al. , 2011; Suzuki et al. , 2011; Yagi and Fukahata, 2011; Yokota et al. , 2011; Yue and Lay, 2011; Frankel, 2013), ionosphere perturbation detection (Heki, 2011; Tsugawa et al. , 2011; Komjathy et al. , 2012), study of Earth free oscillation (Mitsui and Heki, 2012), etc. For those studies, the acquisition of robust seismic waveforms is vital but defective, especially in a real‐time mode. High‐rate Global Positioning System (GPS) is capable of recording seismic waveforms with centimeter‐level accuracy (Genrich and Bock, 2006), regardless of relative kinematic positioning mode (Nikolaidis et al. , 2001; Larson et al. , 2003; Blewitt et al. , 2006, 2009; Bilich et al. , 2008; Crowell …

Investigating the Origin of Seismic Swarms

According to the U.S. Geological Survey's Earthquake Hazards Program, a seismic swarm is “a localized surge of earthquakes, with no one shock being conspicuously larger than all other shocks of the swarm. They might occur in a variety of geologic environments and are not known to be indicative of any change in the long‐term seismic risk of the region in which they occur” (http://vulcan.wr.usgs.gov/Glossary/Seismicity/description_earthquakes.html).

Brief communication "Seismic and acoustic-gravity signals from the source of the 2004 Indian Ocean Tsunami"

Abstract. The great Sumatra-Andaman earthquake of 26 December 2004 caused seismic waves propagating through the solid Earth, tsunami waves propagating through the ocean and infrasound or acoustic-gravity waves propagating through the atmosphere. Since the infrasound wave travels faster than its associated tsunami, it is for warning purposes very intriguing to study the possibility of infrasound generation directly at the earthquake source. Garces et al. (2005) and Le Pichon et al. (2005) emphasized that infrasound was generated by mountainous islands near the epicenter and by tsunami propagation along the continental shelf to the Bay of Bengal. Mikumo et al. (2008) concluded from the analysis of travel times and amplitudes of first arriving acoustic-gravity waves with periods of about 400–700 s that these waves are caused by coseismic motion of the sea surface mainly to the west of the Nicobar islands in the open seas. We reanalyzed the acoustic-gravity waves and corrected the first arrival times of Mikumo et al. (2008) by up to 20 min. We found the source of the first arriving acoustic-gravity wave about 300 km to the north of the US Geological Survey earthquake epicenter. This confirms the result of Mikumo et al. (2008) that sea level changes at the earthquake source cause long period acoustic-gravity waves, which indicate that a tsunami was generated. Therefore, a denser local network of infrasound stations may be helpful for tsunami warnings, not only for very large earthquakes.

Earthquakes and pediatric nephrology: are we prepared?

Sirs, With the recent Haiti earthquake causing significant morbidity and mortality [1], it is now time to look back and analyse our readiness for disaster management. Contrary to our expectations and understanding, earthquakes are common natural disasters from a global point of view. As updated on the home page of the US Geological Survey Earthquake Hazards Program (http://earthquake. usgs.gov/), earthquakes with a magnitude 4.0 or greater occur every day all over the world [2]. Because the number of casualties in a large earthquake is much higher than in other natural disasters, crush syndrome has been recognized to be the most frequent cause of acute kidney injury (AKI) after an earthquake. Kidney failure has been identified by the Centers for Disease Control and Prevention as one of the most urgent public health concerns in Haiti following the 7.0-magnitude earthquake on 12 January 2010 [3]. Historically, recognition and better understanding of acute renal failure was obtained following crush injuries in patients in wartime London in 1940 [4]. The main problems handled by pediatric nephrologists are prevention of AKI (by fluid management), management of AKI (due to sepsis, crush injury and infections), management of hyperkalemia, and renal replacement therapy. Proper and timely transportation of the victims with AKI and those with end stage renal disease (ESRD) to the centre with availability of renal replacement therapy is also required. The logistics of medical supply availability is also an issue [5]. In the face of an imminent emergency situation, dialysis facilities, the AKI and the ESRD community, and emergency response organizations need to execute carefully designed plans, with a well-designed timeline for disaster preparation and response [6]. The experience of the Haitian earthquake identified that the organization of effort was not up to par. Use of the Pediatric Nephrology List Serve by Andrew Aronson allowed for global communication outside of Haiti, but did not allow for communication within Haiti. Having “eyes on site” was important to access the needs of the pediatric population. Constant communication with Dr. Emilo Mena Castro in Santo Domingo in the Dominican Republic allowed for close coverage of care. Utilization of Dr. Castro as a pediatric port of call for the identification of the needs of children with AKI and for distribution of equipment for treatment of AKI was important. Intra-island and intra-Haitian communication was lacking, making it difficult to identify who was in need and where they were located. Further, the lack of available equipment for creatinine or potassium analysis also contributed to care delivery difficulty. It was learned that many pediatric nephrologists throughout the world were willing and ready to help in any way. Local communication and intra-country communication is important to assess and deliver care when needed. S. K. Sethi (*) Division of Pediatric Nephrology, Department of Pediatrics, PGIMER and associated RML Hospital, New Delhi, India 110001 e-mail: sidsdoc@gmail.com

GIS-Based Virtual Geotechnical Database for the St. Louis Metro Area

Research Article| May 01, 2010 GIS-Based Virtual Geotechnical Database for the St. Louis Metro Area JAE-WON CHUNG; JAE-WON CHUNG 1Department of Geological Sciences and Engineering, 1400 North Bishop Avenue, Missouri University of Science and TechnologyRolla, MO 65409 Search for other works by this author on: GSW Google Scholar J DAVID ROGERS J DAVID ROGERS 1Department of Geological Sciences and Engineering, 1400 North Bishop Avenue, Missouri University of Science and TechnologyRolla, MO 65409 Search for other works by this author on: GSW Google Scholar Author and Article Information JAE-WON CHUNG 1Department of Geological Sciences and Engineering, 1400 North Bishop Avenue, Missouri University of Science and TechnologyRolla, MO 65409 J DAVID ROGERS 1Department of Geological Sciences and Engineering, 1400 North Bishop Avenue, Missouri University of Science and TechnologyRolla, MO 65409 Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online ISSN: 1558-9161 Print ISSN: 1078-7275 Copyright © 2010 EEGS Environmental & Engineering Geoscience (2010) 16 (2): 143–162. https://doi.org/10.2113/gseegeosci.16.2.143 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation JAE-WON CHUNG, J DAVID ROGERS; GIS-Based Virtual Geotechnical Database for the St. Louis Metro Area. Environmental & Engineering Geoscience 2010;; 16 (2): 143–162. doi: https://doi.org/10.2113/gseegeosci.16.2.143 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract The St. Louis metropolitan area is the focus of the U.S. Geological Survey's Earthquake Hazard Program's plan for assessing the likely risks of an earthquake emanating from the New Madrid Seismic Zone or the Wabash Valley Seismic Zone, which are the most active seismic zones recognized in the Midwestern United States. The St. Louis metro area includes portions of eight counties located both in Missouri and Illinois that abut the state boundary formed by the Mississippi River. The Illinois and Missouri geological surveys have prepared geologic maps and data sets that employ dissimilar geodata information, differing map units, map scales, and storage formats, with geodata stored in analog or digital formats. This research sought to combine the dissimilar geodata sets and to integrate them into a single Virtual Geotechnical Database within an accepted geographic information system (ArcGIS), which could be manipulated to retrieve subsurface data and to perform an array of spatial analyses. The geodatabase is intended to promote standardization of geologic interpretations between Missouri and Illinois and will be available to other researchers. The existing body of data was manipulated to extract useful information on the surficial geology, loess thickness, bedrock geology, well locations, and measured values of shear wave velocity, which could be conjoined to create stand-alone GIS information layers. “Depth-to-bedrock” refers to the lithologic contact with early Paleozoic-age strata recognized by formational assignments across the two states. Depth-to-bedrock and groundwater table elevations underling the study area were interpolated using geostatistical methods of ordinary kriging and cokriging, respectively. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

OMG Earthquake! Can Twitter Improve Earthquake Response?

Following the 12 May 2008 Wenchuan, China, earthquake, discussion circulated on the Internet describing how the U.S. Geological Survey's earthquake notification lagged behind firsthand accounts sent through Twitter, a popular Internet-based service for sending and receiving short text messages, referred to as “tweets.” A prominent technology blogger, Robert Scoble (http://scobleizer.com), is generally credited for being the first to aggregate and redistribute tweets from people in China who directly experienced and reported the shaking resulting from the Wenchuan earthquake. Subsequent earthquakes generated volumes of earthquake-related tweets, and numerous accounts are on the Web. For example, Ian O'Neill discusses Twitter activity following a magnitude 3.3 Los Angeles earthquake on 24 January 2009 in his blog http://astroengine.com. He showed a remarkable increase in frequency of tweets containing the word “earthquake” after the event and discussed the possibility of a Twitter-based earthquake detector. Similarly, following the 30 March 2009, Morgan Hill, California, magnitude 4.3 earthquake, Michal Migursk (http://mike.teczno.com) noted an increase in earthquake-related tweets. Access to firsthand accounts of earthquake shaking within seconds of an earthquake is intriguing, but is there any reliable information that can be gleaned from the Twitter messages? To explore this question, we provide a quick review of Twitter and its capabilities and investigate the possibility of using the tweets to detect seismic events and produce rapid maps of the felt area. In this exploratory study, we examine the tweets that followed the 30 March 2009 Morgan Hill earthquake. Twitter is a service that allows anyone to send and receive 140-character text messages (tweets) via any Internet-enabled device. Tweets can be sent and received through a Web page, mobile device, or third-party Twitter applications. Tweets can be sent publicly or privately to a specified user. All users who opt to “follow” a Twitter user will receive that user's tweets …

In the Aftermath of Haiti's Earthquake: A Discussion of Lessons Learned

The 12 January 2010 earthquake in Haiti brought massive devastation to that country (see Figure 1). In this week's issue of Eos, three noted seismologists respond to questions from Eos senior writer Randy Showstack in a news roundtable format.Paul Mann, senior research scientist with the Institute for Geophysics at the University of Texas at Austin, has just returned from Haiti, where he and a colleague worked on a fault rupture survey; they plan to conduct an offshore fault survey soon. Glen Mattioli, professor of geosciences at the University of Arkansas, Fayetteville, has been part of a team conducting a Global Positioning System (GPS) survey of Haiti to measure ground deformation following the earthquake and to install a number of continuous GPS sites to examine after slip, viscoelastic relaxation, and the time return to interseismic deformation (see Figure 2). Work by Mann, Mattioli, and their colleagues has been supported through a U.S. National Science Foundation Rapid Response Research ( RAPID) proposal grant provided to Purdue University, with Eric Calais serving as principal investigator. Carol Prentice, a seismologist with the U.S. Geological Survey's Earthquake Hazards Team, has been conducting paleoseismic research on the active faults in the Caribbean region since 1991, including projects on Hispaniola, Puerto Rico, Trinidad, and Jamaica.

Space-time structures of earthquakes

Using the United States Geological Survey global daily data sets for 31 years, we have tabulated the earthquake intensities on a global latitude longitude grid and represented them as a finite sum of spherical harmonics. An interesting aspect of this global view of earthquakes is that we see a low frequency modulation in the amplitudes of the spherical harmonic waves. There are periods when these waves carry larger amplitudes compared to other periods. A power spectral analysis of these amplitudes clearly shows the presence of a low frequency oscillation in time with a largest mode around 40 days. That period also coincides with a well-know period in the atmosphere and in the ocean called the Madden Julian Oscillation. This paper also illustrates the existence of a spatial oscillation in strong earthquake occurrences on the western rim of the Pacific plate. These are like pendulum oscillations in the earthquake frequencies that swing north or south along the western rim at these periods. The spatial amplitude of the oscillation is nearly 10,000 km and occurs on an intraseasonal time scale of 20–60 days. A 34-year long United States Geological Survey earthquake database was examined in this context; this roughly exhibited 69 swings of these oscillations. Spectral analysis supports the intraseasonal timescale, and also reveals higher frequencies on a 7–10 day time scale. These space-time characteristics of these pendulum-like earthquake oscillations are similar to those of the MJO. Fluctuations in the length of day on this time scale are also connected to the MJO. Inasmuch as the atmospheric component of the MJO will torque the solid earth through mountain stresses, we speculate the MJO and our proposed earthquake cycle may be connected. The closeness of these periods calls for future study.

Tsunami hits the Solomon Islands

A magnitude 8.1 earthquake shook the Solomon Islands on 1 April at approximately 7:40 A.M. local time. The earthquake generated a tsunami several meters high that struck many of the islands. The earthquake occurred along the boundary of the Pacific plate where the Australia, Woodlark, and Solomon Sea plates subduct beneath it, according to the U.S. Geological Survey's Earthquake Hazards Program. At least 34 people were killed by the tsunami and several dozen more are still missing, according to the National Disaster Council in the Solomon Islands. The NDC estimates that 900–2500 homes were destroyed by the tsunami, displacing about 5500 people

Implementing ShakeMap for the New Madrid Seismic Zone

Immediately after a damaging earthquake, emergency managers rapidly seek answers to many important questions: Where is the worst and/or least damage? What equipment and personnel must be mobilized and to what extent? ShakeMap was developed by the U.S. Geological Survey Earthquake Hazards Program to assist in answering these questions by producing near-real-time maps of ground motion and shaking intensity following significant earthquakes (Wald et al. 2004). To produce maps, ShakeMap mimics a dense array of seismometers by using an attenuation relationship to model peak ground motions at virtual or “phantom” stations between existing seismic stations. The modeled data are corrected for site amplification (Borcherdt 1994) and used to produce an instrumental intensity map, a hybrid Modified Mercalli map based on instrumental recording (Wald et al. 1999a). ShakeMap software, implemented predominantly in the Western United States (Northern and Southern California; Salt Lake City, Utah; and Seattle, Washington), requires a degree of regional customization to ensure accuracy of the maps. We report here on the Eastern United States software customization required for implementation of ShakeMap in the New Madrid Seismic Zone (NMSZ) and verification of the resulting maps. The New Madrid region has a relatively high seismic hazard, yet very little data exist for large earthquakes. To estimate peak ground motions for magnitudes greater than 6.0, we qualitatively compared scenario ShakeMaps using different attenuation relationships and intensity regressions to a magnitude 7.4 scenario produced by the USGS Memphis hazard mapping group (Chris Cramer, personal communication 2005; see also http://www.ceri.memphis.edu/usgs/products/regional.html). For smaller events (M < 6) we used the 10 February 2005 magnitude 4.1 earthquake near Blytheville, Arkansas, as an example. The study location is in the Upper Mississippi Embayment of the Central and Eastern United States (CEUS) and is centered on the NMSZ (figure 1). The area covers a four-by-four-degree grid from …

Program cut reduces quake studies

The proposed decrease of $15 million in the Fiscal Year 1992 budget for the U.S. Geological Survey's Earthquake Hazards Reduction Program (EHRP) will significantly reduce earthquake studies. Congress provided expanded support of the program in FY91 as a continuation of support following the 1989 Loma Prieta earthquake, when Congress gave a supplemental appropriation. As created by the Earthquake Hazards Reduction Act of 1977, EHRP is a major component of the National Earthquake Hazards Reduction Program, along with the Federal Emergency Management Agency, National Science Foundation, and the National Institute of Standards and Technology.Betty Goodrich, Acting Budget Officer of USGS, notes that the cut is in response to a “tight fiscal situation and not that Congress is against the earthquake program.” She also attributes the reduction in the program to competing priorities among other major initiatives. “EHRP just did not make it through,” she said.

Clues to prehistoric earthquakes?

A record of ancient earthquakes that extends over thousands of years may be ‘frozen’ into sediments of natural lakes, according to a recent issue of the U.S. Geological Survey's Earthquake Information Bulletin.‘… historic records of earthquakes are too short to allow a true assessment of recurrence intervals; therefore a method has been needed that will enable the seismic history of a region to be extended beyond the limit of historic time,’ writes John Sims of the USGS Menlo Park, California, office. ‘One place where a record of ancient seismic history might be preserved is in lake sediments’.