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Analytical Tools Constructing a seismicity model, in a nutshell, means formulating a realistic model of earthquake occurrences on a fault, in a subduction zone, or within an area. A modeler would collect: Most seismicity models are formulated as a combination of a Gutenberg-Richter (GR) and a characteristic earthquake model. The Gutenberg-Richter model describes the occurrence…
Analytical Tools Seismicity of the United States: USGS Model Formulation Earthquakes are common throughout the United States, with the highest activity concentrated in the western states, Alaska, and Hawaii. However, the central and eastern U.S. also experiences occasional damaging seismic events. According to the USGS report, 27 states have experienced potentially damaging earthquakes of magnitude…
Analytical Tools Geodetic data provides valuable information on how a region is being strained and its potential to experience earthquakes. Over the last few decades, there have been concerted efforts to develop databases of global surface strain rates, aiming to assess regional earthquake hazards. Figure 1 shows a map of regional strain rates for Europe,…
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Decades of research have produced methodologies for interpreting regional rates of surface strain‑rate measurements in terms of regional rates of seismic moment accumulation. Because seismic moment quantifies the strain released by earthquakes, framing regional strain buildup in terms of moment rate offers a meaningful way to assess the potential for future seismic activity. In this…
Active seismic regions release their tectonic strain mostly through earthquakes of different magnitudes on faults and subduction zones. For hazard analysis, it is necessary to quantify the rates of occurrences of these different magnitude earthquakes on different regional seismic sources. Seismologists refer to this process as building magnitude-rate distributions (MRDs) for seismic sources. The most…
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Sand Box: Search/Plot Faults in Western US to Get Details The USGS 2023 Seismicity Model for the western United States is built from an exceptionally large dataset: 553,115 earthquake scenarios. These scenarios represent the expected seismic behavior of 1,016 regional crustal faults, referred to in the USGS report as parent faults (see Figure 1). Many…
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Sand Box: Search/Plot Earthquake Scenarios to Get Details and Conduct Ground Motion Analysis The 2023 USGS seismicity model for faults in the western United States presents the regional seismicity through many earthquake scenarios that rupture multiple fault sections. This reflects decades of observations that large crustal earthquakes often rupture sections of different neighboring faults. The…
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Sand Box: Construct and evaluate magnitude-rate distribution scenarios Many large faults and subduction zones do not follow the typical Gutenberg–Richter (GR) magnitude–rate distribution (MRD). In many cases, the observed or inferred rates of large‑magnitude earthquakes—based on historical records or paleoseismic evidence—are higher than what a standard GR distribution would predict from the rates of small…
Sand Box: Construct and evaluate magnitude-rate distribution scenarios Active seismic regions release accumulated tectonic strain primarily through earthquakes of various magnitudes occurring on faults and subduction zones. For seismic hazard analysis, it is essential to quantify how often earthquakes of different magnitudes occur on each seismic source. Seismologists refer to this process as constructing magnitude–rate…
Read More “Gutenberg-Richter Distribution: Technical Details” »