Publications

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...

The occurrence of debris flows during the September 2013 northern Colorado floods took the emergency management community by surprise. The September 2013 debris flows in the Colorado Front Range initiated from shallow landslides in colluvium. Most occurred on south- and east-facing slopes on the walls of steep canyons in crystalline rocks and on sedimentary hogbacks. Previous studies...

In the past decades, many different approaches have been developed in the literature to quantify the load-carrying capacity and geotechnical stability (or the Factor of Safety, F_s) of variably saturated hillslopes. Much of this work has focused on a deterministic characterization of hillslope stability. Yet, simulated F_s values are subject to considerable uncertainty due to our...

Large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking. Most moderate- and large-magnitude earthquakes trigger landslides, ranging from small failures in the soil cover to massive, devastating rock avalanches. Some landslides dam rivers and impound lakes, which can collapse days to centuries later, and flood mountain valleys...

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...

Lobate stony landforms occur on steep slopes at high latitudes on Mars. We demonstrate active boulder movement at seven such sites. Sub-meter-scale boulders frequently move distances of a few meters. The movement is concentrated in the vicinity of the lobate landforms but also occurs on other slopes. This provides evidence for a new, common style of activity on Mars, which may play an...

At the eastern end of the 1957 Andreanof Islands magnitude-8.6 earthquake rupture, Driftwood Bay (Umnak Island) and Stardust Bay (Sedanka Island) lie along presently locked and creeping parts of the Aleutian megathrust, respectively, based on satellite geodesy onshore. Both bays, located 200-km apart, face the Aleutian trench and harbor coastal evidence for tsunami inundation in 1957...

We estimate earthquake ground-motion variability in the central and eastern U.S. (CEUS) by varying the model parameters of a deterministic physics-based and a stochastic site-based simulation method. Utilizing a moderate-magnitude database of recordings, we simulate ground motions for larger-magnitude scenarios M6.0, 6.5, 7.0, 7.5, and 8.0. For the physics-based method, we vary the...

: In recent years, ground motion models used in probabilistic seismic hazard analyses (PSHA) have evolved from the traditional approach of using ground motion prediction equations (GMPEs) to using ground motion time series models. The purpose of this paper is to develop an approach to perform a probabilistic seismic hazard analysis using stochastic site-based simulation techniques. These

In the U.S., seismic design values are determined mostly through a risk-targeting process, which combines information about the expected collapse fragility of code-designed structures with seismic hazard at a site. However, this target only applies where the risk-targeted ground motions govern the design. In other areas, primarily close to active faults, seismic design values are reduced...

The recent proliferation of high-resolution ( 3-m spatial resolution) digital topography datasets opens a spectrum of geodetic applications in differential topography, including the quantification of coseismic vertical displacement fields. Most investigations of coseismic vertical displacements to date rely, in part, on pre- or post-event lidar surveys that are intractable or non...

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...