Publications

The interaction of aseismic and seismic slip before and after an earthquake is fundamental for both earthquake nucleation and postseismic stress relaxation. However, it can be difficult to determine where and when aseismic slip occurs within the seismogenic zone because geodetic techniques are limited to detecting moderate to large slip amplitudes or long duration small slip amplitudes...

If brittle fault strength depends only on friction, slip instability is discouraged at low effective normal stress, σ. Stress drop and the critical stiffness necessary for unstable sliding both vanish with σ; small earthquakes cannot occur. Very low σ is inferred in the source region of low-frequency earthquakes (LFEs) on the San Andreas fault (SAF). Moreover, if pore pressure, p, is...

Glen Torridon (GT) is a recessive-trough feature on the northwestern slope of “Mt. Sharp” in Gale crater, Mars with the highest Fe-/Mg-phyllosilicates abundances detected by the Curiosity rover to date. Understanding the origin of these clay minerals and their relationship with diagenetic processes is critical for reconstructing the nature and habitability of past surface and subsurface

This study utilizes instruments from the Curiosity rover payload to develop an integrated paleoenvironmental and compositional reconstruction for the 65-m thick interval of stratigraphy comprising the Hartmann's Valley and Karasburg members of the Murray formation, Gale crater, Mars. The stratigraphy consists of cross-stratified sandstone (Facies 1), planar-laminated sandstone (Facies 2)...

Knowledge about local seismic site conditions provides critical information to account for site effects that are commonly observed in strong motion recordings. Certainly, other wave propagation effects can influence these observations, which are attributable to variations in material properties of the paths traveled by the waves, as well as the characteristics of the seismic source...

The Ulleung Basin Gas Hydrate field expeditions in 2007 (UBGH1) and 2010 (UBGH2) sought to assess the Basin's gas hydrate resource potential. Coring operations in both expeditions recovered evidence of gas hydrate, primarily as fracture-filling (or vein type) morphologies in mainly silt-sized, fine-grained sediment, but also as pore-occupying hydrate in the coarser-grained layers of...

We describe the flexible multimethod seismic site characterization technique for obtaining shear-wave velocity (VS) profiles and derivative information, such as the time-averaged VS of the upper 30 m (VS30). Simply stated, the multimethod approach relies on the application of multiple independent noninvasive site characterization acquisition and analysis techniques utilized in a flexible...

The U.S. Geological Survey (USGS) National Earthquake Information Center (NEIC) routinely produces finite‐fault models following significant earthquakes. These models are spatiotemporal estimates of coseismic slip critical to constraining downstream response products such as ShakeMap ground motion estimates, Prompt Assessment of Global Earthquake for Response loss estimates, and ground...

Land subsidence is a settling, sinking, or collapse of the land surface. In the southeastern United States, subsidence is frequently observed as sinkhole collapse in karst environments, wetland degradation and loss in coastal and other low-lying areas, and inundation of coastal urban communities. Human activities such as fluid extraction, mining, and overburden alteration can cause or...

We examine fossil foraminiferal assemblages from 20 sediment cores to assess sudden relative sea-level (RSL) changes across three mud-over-peat contacts at three salt marshes in northern Humboldt Bay, California (~44.8°N, -124.2°W). We use a validated foraminiferal-based Bayesian transfer function to evaluate the variability of subsidence stratigraphy at a range of 30-6000 m across an...

Structure from motion (SfM) photogrammetry is an increasingly common technique for measuring landscape change over time by deriving 3D point clouds and surface models from overlapping photographs. Traditional change detection approaches require photos that are geotagged with a differential GPS (DGPS) location, which requires expensive equipment that can limit the ability of communities...

This chapter introduces seismic monitoring of structural systems for buildings and begins with a historical background of this topic in the United States. After providing the historical context, the chapter reviews common seismic instrumentation issues such as utilization of data, code versus extensive instrumentation, free-field instrumentation, record synchronization requirements and...