Publications

To better understand the potential for amplified ground shaking at sites that house critical infrastructure, the U.S. Geological Survey (USGS) evaluated shear-wave velocities (VS) at six strong-motion recording stations in Southern California Edison facilities in southern California. We calculated VS30 (time-averaged shear-wave velocity in the upper 30 meters [m]), which is a parameter...

We assess how well the Next-Generation Attenuation-West 2 (NGA-West2) ground-motion models (GMMs), which are used in the US Geological Survey’s (USGS) National Seismic Hazard Model (NSHM) for crustal faults in the western United States, predict the observed basin response in the Great Valley of California, the Reno basin in Nevada, and Portland and Tualatin basins in Oregon. These GMMs...

We introduce a Python package for computing focal mechanism solutions. This algorithm, which we refer to as SKHASH, is largely based on the HASH algorithm originally written in Fortran over 20 yr ago. HASH innovated the use of suites of solutions, spanning the expected errors in polarities and takeoff angles, to estimate focal mechanism uncertainty. SKHASH benefits from new features with...

The recent developments in general viscoelastic ray theory provide a rigorous mathematical framework for anelastic seismic tomography. They provide closed‐form solutions of forward ray‐tracing and simple inverse problems for anelastic horizontal and spherical layered media with material gradients. They provide ray‐tracing computation algorithms valid for all angles of incidence that...

Radiocarbon dates of sedimentary deposits include the elapsed time between formation of the organic material and deposition at the sample site, known as the inherited age. Long inherited ages reduce the accuracy of estimates of the timing of depositional events used to infer paleoclimate change, fire histories, and paleoearthquake timing. An inherited age distribution combines the...

The Seismological Society of America (SSA) topical conference, Future Directions for Physics‐Based Ground Motion Modeling, was held in Vancouver, Canada, on 10–13 October 2023, co‐sponsored by the Seismological Society of Japan and co‐chaired by Annemarie Baltay of the U.S. Geological Survey and Hiroshi Kawase of Kyoto University. This meeting brought together many researchers and...

The ShakeAlert Earthquake Early Warning (EEW) system aims to issue an advance warning to residents on the West Coast of the United States seconds before the ground shaking arrives, if the expected ground shaking exceeds a certain threshold. However, residents in tall buildings may experience much greater motion due to the dynamic response of the buildings. Therefore, there is an ongoing...

This report is an update to the presentation by Schulz (1989) introducing potential users to the creepmeter data collected between the publication of Schulz’s report and mid-2020. The creepmeter network monitors aseismic, surface slip at various locations on the Hayward, Calaveras, and San Andreas Faults in northern and central California. There are different designs of creepmeters and...

Earthquakes and other natural events sometimes shake the seafloor near coastlines severely enough to cause underwater avalanches that rush down steep slopes, scouring the seabed and carrying sediment to greater depths. These fast-moving sediment-laden flows, called turbidity currents, have at times damaged underwater infrastructure like pipelines and communications cables, as they did...

Two earthquake sequences occurred a year apart at the Mendocino Triple Junction in northern California: first the 20 December 2021 �w 6.1 and 6.0 Petrolia sequence, then the 20 December 2022 �w 6.4 Ferndale sequence. To delineate active faults and understand the relationship between these sequences, we applied an automated deep‐learning workflow to create enhanced and relocated...

Model development in the Next Generation Attenuation-East (NGA-East) project included two components developed concurrently and independently: (1) earthquake ground-motion models (GMMs) that predict the median and aleatory variability of various intensity measures conditioned on magnitude and distance, derived for a reference hard-rock site condition with an average shear-wave velocity...

Executive Summary The U.S. Geological Survey has a long history of contributions to the understanding and resolution of various scientific questions related to earthquakes associated with human activities, referred to as induced seismicity. Work started with the Rocky Mountain Arsenal studies in the 1960’s (Healy and others, 1968) when it was first discovered that fluid waste-disposal...