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The Graizer-Kalkan ground-motion prediction equation (GMPE) for peak ground acceleration (PGA) constitutes a series of filters, each of which represents a certain physical phenomenon affecting the radiation of seismic waves from the source. The performance of this GMPE is examined by using about 14,000 records from 245 worldwide shallow crustal events. The recorded data and predictions show an excellent match as far as 100 km from the fault. Beyond 100 km, the data generally show faster attenuation on the order of Rrup−4due to a relatively low Q (as in the western United States) or slower attenuation on the order of Rrup−1.5due to a high Q (as in the central and eastern United States). An improved GMPE is developed to account for regional variations in ground motion attenuation. The The new GMPE produces a better match to recorded data up to 500 km from the fault.

Wedescribe aweighted-average approach for incorporating varioustypes of data (observed peak ground motions and intensities and estimates from ground- motion prediction equations) into theShakeMap ground motion and intensity mapping framework.ThisapproachrepresentsafundamentalrevisionofourexistingShakeMap methodology. In addition, the increased availability of near-real-time macroseismic intensitydata,thedevelopmentofnewrelationshipsbetweenintensityandpeakground motions, and new relationships to directly predict intensity from earthquake source information have facilitated the inclusion of intensity measurements directly into ShakeMap computations. Our approach allows for the combination of (1) direct observations (ground-motion measurements or reported intensities), (2) observations converted from intensity to ground motion (or vice versa), and (3) estimated ground motionsandintensities frompredictionequationsornumerical models.Critically,each oftheaforementioneddatatypesmustincludeanestimateofitsuncertainties,including those caused by scaling the influence of observations to surrounding grid points and those associated with estimates given an unknown fault geometry. The ShakeMap ground-motion and intensity estimates are an uncertainty-weighted combination of these various data and estimates. A natural by-product of this interpolation process is an estimate of total uncertainty at each point on the map, which can be vital for comprehensive inventory loss calculations. We perform a number of tests to validate this new methodology and find that it produces a substantial improvement in the accuracy of ground-motion predictions over empirical prediction equations alone.

We present an Atlas of ShakeMaps and a catalog of human population expo- sures to moderate-to-strong ground shaking (EXPO-CAT) for recent historical earthquakes (1973-2007). The common purpose of the Atlas and exposure catalog is to calibrate earth- quake loss models to be used in the US Geological Survey's Prompt Assessment of Global EarthquakesforResponse(PAGER).ThefullShakeMapAtlascurrentlycomprisesover5,600 earthquakes from January 1973 through December 2007, with almost 500 of these maps con- strained—tovaryingdegrees—byinstrumentalgroundmotions,macroseismicintensitydata, community internet intensity observations, and published earthquake rupture models. The catalog of human exposures is derived using current PAGER methodologies. Exposure to discrete levels of shaking intensity is obtained by correlating Atlas ShakeMaps with a global population database. Combining this population exposure dataset with historical earthquake lossdata,suchasPAGER-CAT,providesausefulresourceforcalibratinglossmethodologies against a systematically-derived set of ShakeMap hazard outputs. We illustrate two example uses for EXPO-CAT; (1) simple objective ranking of country vulnerability to earthquakes, and; (2) the influence of time-of-day on earthquake mortality. In general, we observe that countriesinsimilargeographicregionswithsimilarconstructionpracticestendtoclusterspa- tiallyintermsofrelativevulnerability.Wealsofindlittlequantitativeevidencetosuggestthat time-of-day is a significant factor in earthquake mortality. Moreover, earthquake mortality appears to be more systematically linked to the population exposed to severe ground shaking (Modified Mercalli Intensity VIII+). Finally, equipped with the full Atlas of ShakeMaps, we merge each of these maps and find the maximum estimated peak ground acceleration at any grid point in the world for the past 35years. We subsequently compare this "composite

When a potentially damaging earthquake occurs, utility and other lifeline managers, emergency responders, and other critical users have an urgent need for information about the impact on their particular facilities so they can make appropriate decisions and take quick actions to ensure safety and restore system functionality. ShakeMap, a tool used to portray the extent of potentially damaging shaking following an earthquake, on its own can be useful for emergency response, loss estimation, and public information. However, to take full advantage of the potential of ShakeMap, we introduce ShakeCast. ShakeCast facilitates the complicated assessment of potential damage to a user's widely distributed facilities by comparing the complex shaking distribution with the potentially highly variable damageability of their inventory to provide a simple, hierarchical list and maps of structures or facilities most likely impacted. ShakeCast is a freely available, post-earthquake situational awareness application that automatically retrieves earthquake shaking data from ShakeMap, compares intensity measures against users’ facilities, sends notifications of potential damage to responsible parties, and generates facility damage maps and other Web-based products for both public and private emergency managers and responders.

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The 2004 Mw 6.0 Parkfield earthquake of 28 September 2004 occurred on the San Andreas Fault near the small town of Parkfield in central California. As a result of a widely accepted likelihood of an earthquake in the area, a large number of strong-motion stations and other types of seismic stations had been deployed in the area. The Parkfield earthquake occurred along the same segment of the San Andreas Fault that ruptured during the 1966 Parkfield earthquake, resulting in a unique set of strong-motion measurements by arrays designed specifically for the purpose of recording an event along this fault segment. The most extensive and dense set of near-fault strong-motion recordings yet obtained for any earthquake in California was obtained in this event. This paper provides a detailed description of the arrays and the resultant strong-motion measurements of the mainshock, as well as preliminary observations. We also invite interested parties to participate in the Turkey Flat blind prediction experiment, described later in the paper. More general preliminary seismological results for this earthquake can be found in Langbein et al. (2005, this issue). During the Parkfield earthquake, a total of 56 three-component strong-motion recordings of acceleration were obtained within 20 km of the fault, with 48 of these being within 10 km of the fault. The strong-motion measurements by the Parkfield strong-motion array in the near-fault region are highly varied, with significant variations over relatively short distances. A map of near-fault peak acceleration (Figure 1) shows striking variations over only a few kilometers. The map also shows a concentration of strong shaking at both ends of the fault. Measurements in the near-fault region range from 0.13 g to more than 2.5 g (which may be the highest acceleration recorded to date). The largest peak accelerations occurred near the northwest end …

When an earthquake occurs, the U. S. Geological Survey (USGS) ShakeMap portrays the extent of potentially damaging shaking. In turn, the ShakeCast system, a freely-available, post-earthquake situational awareness application, automatically retrieves earthquake shaking data from ShakeMap, compares intensity measures against users’ facilities, sends notifications of potential damage to responsible parties, and generates facility damage assessment maps and other web-based products for emergency managers and responders. ShakeCast is particularly suitable for earthquake planning and response purposes by Departments of Transportation (DOTs), critical facility and lifeline utilities, large businesses, engineering and financial services, and loss and risk modelers. Recent important developments to the ShakeCast system and its user base are described. The newly-released Version 3 of the ShakeCast system encompasses advancements in seismology, earthquake engineering, and information technology applicable to the legacy ShakeCast installation (Version 2). In particular, this upgrade includes a full statistical fragility analysis framework for general assessment of structures as part of the near real-time system, direct access to additional earthquake-specific USGS products besides ShakeMap (PAGER, DYFI?, tectonic summary, etc.), significant improvements in the graphical user interface, including a console view for operations centers, and custom, user-defined hazard and loss modules. The release also introduces a new adaption option to port ShakeCast to the "cloud". Employing Amazon Web Services (AWS), users now have a low-cost alternative to local hosting, by fully offloading hardware, software, and communication obligations to the cloud. Other advantages of the "ShakeCast Cloud" strategy include (1) Reliability and robustness of offsite operations, (2) Scalability naturally accommodated, (3), Serviceability, problems reduced due to software and hardware uniformity, (4) Testability, freely available for new users, (5) Remotely supported, allowing expert-facilitated maintenance, (6) Adoptability, simplified with disk images, and (7) Security, built in at the very high level associated with AWS. The ShakeCast user base continues to expand and broaden. For example, Caltrans, the prototypical ShakeCast user and development supporter, has been providing guidance to other DOTs on the use of the National Bridge Inventory (NBI) database to implement fully-functional ShakeCast systems in their states. A long-term goal underway is to further "connect the DOTs" via a Transportation Pooled Fund (TPF) with participating state DOTs. We also review some of the many other users and uses of ShakeCast. Lastly, on the hazard input front, we detail related ShakeMap improvements and ongoing advancements in estimating the likelihood of shaking-induced secondary hazards at structures, facilities, bridges, and along roadways due to landslides and liquefaction, and implemented within the ShakeCast framework.

A simple procedure is presented to resolve locations of regional earthquakes with poor quality of recorded phases and/or a very large gap in seismograph recording geometry. In solving earthquake locations, we use a modified G matrix containing S - P time intervals and P - P and S - S time differences between stations and a forward method. Unlike the regular G matrix, which consists of three spatial parameters ( x, y, z ) and one timing parameter ( t ), the modified G matrix contains only two spatial parameters ( x, y ) and a fixed depth ( z ). The origin time parameter is eliminated by using only relative time intervals. In the new G matrix, two base equations instead of one are used. The S - P time intervals constrain epicentral distance, and P - P and S - S time differences constrain the distribution of azimuth. In searching for epicenters, we first divide the modified G matrix based on individual time intervals then map deviations between theoretical and observed time intervals into logic space using the fuzzy logic technique. Resolutions of earthquake locations are enhanced in the logic space by applying logic operations among individual G matrices. Final locations are derived by searching for a center of gravity in the output matrix. Test results indicate that this method effectively avoids the local minimum problem encountered by generalized inverse methods when data are recorded by small aperture arrays from earthquakes outside the arrays or when large errors occur in phase readings.

For 35 years, strong reflected phases from the sill-like, mid-crustal Socorro magma body (SMB) have been observed on microearthquake seismograms recorded in the central Rio Grande rift, New Mexico. In 1979, the lateral extent of the SMB was estimated at 1700 km2 by mapping reflection points for 220 observed SzS arrivals. We have remapped the magma body using 697 PzP, 2169 SzP, and 2589 SzS reflections observed on seismograms recorded between 1975 and 1995 by New Mexico Tech seismic networks. These data indicate that the SMB covers an area greater than 3400 km2. By comparing the distribution of observed reflection points with the distribution of all possible reflection points, limits can be set for the northern and southern boundaries of the SMB. The ∼80 km north-south extent of the SMB falls just inside a ∼100-km north-south range of enhanced seismicity near Socorro. This area, the Socorro seismic anomaly (SSA), covers ∼5000 km2 and has the same elliptical shape as the outline of the SMB based on observed reflection points. The close spatial relation between the SSA and the mid-crustal magma body along their northern and southern boundaries suggests that the observed seismicity can be used to place limits on the eastern and western boundaries of the magma body. Using the distribution of earthquakes within the SSA over the last 34 years, the maximum east-west extent of the SMB is Our data indicates that the upper surface of the magma body displays no regional dip. Considering timing errors, maximum possible relief on the magma body surface is ±0.50 km.

Following a major earthquake, one of Caltrans' most critical tasks is to assess the condition of all potentially impacted bridges and roadway corridors in the state highway system. Timely response is important to ensure public safety, guide emergency vehicle traffic, and re-establish critical lifeline routes. In the past, bridge inspection teams had difficulties setting priorities immediately following an earthquake, because they lacked precise information about where the worst shaking and, most likely, the greatest damage had occurred. In 2005 Caltrans initiated a contract with the United States Geological Survey (USGS) to develop and implement a Caltrans-specific version of their ShakeCast system, a post-event software analysis tool that was anticipated to change the way Caltrans responds following a major earthquake. ShakeCast is a web-based application that automatically retrieves measured earthquake shaking data, analyzes it against individual bridge performance characteristics, and generates inspection prioritization emails and other web-based products for emergency responders within minutes of an event. Benefits have already been realized over the course of the test deployment phase. The ShakeCast system has proved to be a valuable tool for post-earthquake response for Caltrans during real events as well as for scenario planning exercises.

The U. S. Geological Survey (USGS) ShakeCast system is a freely-available, post-earthquake situational awareness application that automatically retrieves earthquake shaking data from ShakeMap, compares intensity measures against users' facilities, sends notifications of potential damage to responsible parties, and generates facility damage assessment maps and other Web-based products for emergency managers and responders. The ShakeMap/ShakeCast combined system allows a consistent approach for the evaluation of facility performance using the ShakeMap methodology by combining observations with ground motion predictions and covers major geographic regions and earthquakes, real-time, historical, and scenario, worldwide. We present common approaches to assessing facility impact estimates by combining measured or estimated ground-motion parameters with vulnerability functions. Vulnerability functions can be pre-computed, use one of these ground-motion parameters as input, and produce a multi-state discrete output of damage likelihood (or, inspection priorities). Two custom modules for evaluating Arias Intensity and Newmark landslide displacements are presented as examples of using the ShakeCast application with more advanced, customized damage functions.