ShakeMap operations, policies, and procedures

Abstract

The US Geological Survey’s ShakeMap is used domestically and globally for post-earthquake emergency management and response, engineering analyses, financial instruments, and other decision-making activities. Recent developments in the insurance, reinsurance, and catastrophe bond sectors link payouts of potentially hundreds of millions of dollars to ShakeMap products. Similarly, building codes, post-earthquake building damage forensic evaluations, and geotechnical evaluations often rely on estimated peak response-spectral values for site-specific evaluations that may lead to costly analyses, retrofits, or other expenditures. Given such activities, financial, engineering, and other technical users demand processing specifications and a metadata trail for actuarial, escrow, and forensic purposes for each significant earthquake. Recent inquiries include how and why maps change with time, how to interpret metadata, and how to obtain the creation and update history of various map layers. Similarly, the collection of ShakeMap scenarios and historical ShakeMaps—either created in earlier versions or rerun as part of the latest version of the ShakeMap Atlas—warrant a full explanation of the inputs, processing, and archiving given their contribution to fragility curve development and loss model calibration. For these reasons, in addition to event-specific ShakeMap metadata and a comprehensive online ShakeMap Manual, we have crafted this practice paper to answer several of the most frequently asked technical questions. We also describe an application programming interface (API) for accessing site-specific shaking metrics and their uncertainties for earthquake forensic purposes in a consistent fashion. In all, we describe the advantages of employing ShakeMaps for these critical purposes as well as describe their limitations and uncertainties, offering an extensive set of instructions and disclaimers that can be referenced by ShakeMap users.

How Low Should We Alert? Quantifying Intensity Threshold Alerting Strategies for Earthquake Early Warning in the United States

“…These ShakeMaps were produced by the National Earthquake Information Center (NEIC) using the most recent version of the USGS ShakeMap software (version 4; Worden & Wald, 2016). All ShakeMaps incorporate finite fault slip information, ground‐motion observations from seismic sensors, and USGS “Did You Feel It?” (DYFI) reports of observed shaking intensities, where available (Wald et al., 2021; Worden & Wald, 2016).…”

“…All Shake-Maps incorporate finite fault slip information, ground-motion observations from seismic sensors, and USGS "Did You Feel It?" (DYFI) reports of observed shaking intensities, where available (Wald et al, 2021;Worden & Wald, 2016).…”

Use of scenario earthquakes for seismic hazard assessment in low-seismicity, stable continental regions: A case study from Indiana, USA

“…Uncertainties of V S30 can be reduced by up to 16% by incorporating V S30 measurements and empirical amplification factors, but this is often not possible or poorly constrained in SCRs due to limited measurements (Thompson and Wald, 2016). V S30 uncertainty is not quantified or accounted for in the current version of ShakeMap, but it remains an area of active research (Wald et al, 2022). Regional studies of ground motions in the Wabash Valley indicate that site-specific amplification values can increase PGA by 25%, 0.2 s by 50%, and 1.0 s spectral acceleration by 30% on average (Haase et al, 2011; Haase and Nowack, 2011).…”

Validation of physics-based ground shaking scenarios for empirical fragility studies: the case of the 2009 L’Aquila earthquake

“…As a matter of fact, the spatial distribution of ground motion intensity is typically inferred either by ShakeMaps (Worden et al 2020;Wald et al 2021), in case a sufficient number of records is available, or by empirical GMPEs (Erdik 2017), as it is often the case for historical earthquakes with no instrumental records. In all such cases, there is a large level of uncertainty when a ground motion level is associated with the specific site where an earthquake effect is observed.…”