Publications

La Honda, California, is a small town in unincorporated San Mateo County, located on the west edge of the San Francisco Peninsula in the Santa Cruz Mountains, between San Francisco and San Jose. The Scenic Drive area of La Honda has experienced several past episodes of landslide motion, which were documented in 1998, 2005, and 2006. This report documents the movement of the upper Scenic...

Numerical simulations of earthquake ground motions are used both to anticipate the effects of hypothetical earthquakes by forward simulation and to infer the behaviour of the real earthquake source ruptures by the inversion of recorded ground motions. In either application it is necessary to assume some Earth structure that is necessarily inaccurate and to use a computational method that...

The study of the Moho beneath thick sedimentary basins involving natural earthquakes is challenging, as low‐velocity materials often cause strong reverberations that mask Moho signals. Here, we develop a method to determine the depth of the Moho by taking advantage of the presence of the sediments. The method utilizes the first Pn crustal multiple from regional earthquakes PnPn and its

We test the Japanese ground‐motion‐based earthquake early warning (EEW) algorithm, propagation of local undamped motion (PLUM), in southern California with application to the U.S. ShakeAlert system. In late 2018, ShakeAlert began limited public alerting in Los Angeles to areas of expected modified Mercalli intensity (⁠IMMI⁠) 4.0+ for magnitude 5.0+ earthquakes. Most EEW systems...

Deep sedimentary basins amplify long-period shaking from seismic waves, increasing the seismic hazard for cities within such basins. We perform 3-D simulations of point source earthquakes distributed around the Seattle and Tacoma basins in Washington State, to examine the dependence of basin amplification on source azimuth, depth, and earthquake type. For periods between 1-10 s, the...

Core samples from the International Ocean Discovery Program (IODP) Expedition 366 were tested in the laboratory to determine permeability, porosity, density, and frictional strength and their relation to mineralogy as part of an effort to understand hydro-mechanical processes at convergent plate margins. Seven samples were tested from a depth range of 19.6 to 197.9 m below the sea floor...

To improve models of ground motion estimation and probabilistic seismic hazard analyses, the engineering seismology field is moving toward developing fully nonergodic ground motion models, models specific for individual source‐to‐site paths. Previous work on this topic has examined systematic variations in ground‐motion along particular paths (from either recorded or simulated earthquake...

Oklahoma is one of the most seismically active places in the United States as a result of industry activities. In order to characterize the fault networks responsible for these earthquakes in Oklahoma, we relocated a large-scale template matching catalog between 2010-2016 using the GrowClust algorithm . This relocated catalog is currently the most complete statewide catalog for Oklahoma...

In the months before he passed away, Jack Boatwright asked us to review a manuscript on source properties, specifically stress drop, of earthquakes in northeastern North America (NENA). This manuscript originated in research funded by the U.S. Nuclear Regulatory Commission (NRC), described in his final report to NRC and published as USGS Open-File Report 2018-1073 (Boatwright, 2018). We...

We analyzed a kinematic earthquake rupture generator that combines the randomized spatial field approach of Graves and Pitarka (Bull Seismol Soc Am 106:2136–2153, 2016) (GP2016) with the multiple asperity characterization approach of Irikura and Miyake (Pure Appl Geophys 168:85–104, 2011) (IM2011, also known as Irikura recipe). The rupture generator uses a multi-scale hybrid approach...

The Fort Rock dome, in Yavapai County, Ariz., is a roughly circular geologic structure in plan view, 2.5 km in diameter, that is similar in many ways to an impact crater; however, it is a structural dome caused by a potassic mafic intrusion at depth, and the crater-like depression in its center is erosional in origin. The Aquarius Mountains, west of the Fort Rock dome, in Mohave County...

The United States Geological Survey (USGS) National Crustal Model (NCM) is being developed to assist in the modeling of seismic hazards across the conterminous United States, specifically by improving estimates of site response. The NCM is composed of geophysical profiles, extending from the Earth’s surface into the upper mantle, constructed from 5 primary elements: 1) depth to bedrock...