We present results from a prototype experiment in which we actively induce, observe, and quantify in situ nonlinear sediment response in the near surface. This experiment was part of a suite of experiments conducted during August 2004 in Garner Valley, California, using a large mobile shaker truck from the Network for Earthquake Engineering Simulation (NEES) facility. We deployed a dense accelerometer array within meters of the mobile shaker truck to replicate a controlled, laboratory-style soil dynamics experiment in order to observe wave-amplitudedependent sediment properties. Ground motion exceeding 1g acceleration was produced near the shaker truck. The wave field was dominated by Rayleigh surface waves and ground motions were strong enough to produce observable nonlinear changes in wave velocity. We found that as the force load of the shaker increased, the Rayleighwave phase velocity decreased by as much as ∼30% at the highest frequencies used (up to 30 Hz). Phase velocity dispersion curves were inverted for S-wave velocity as a function of depth using a simple isotropic elastic model to estimate the depth dependence of changes to the velocity structure. The greatest change in velocity occurred nearest the surface, within the upper 4 m. These estimated S-wave velocity values were used with estimates of surface strain to compare with laboratory-based shear modulus reduction measurements from the same site. Our results suggest that it may be possible to characterize nonlinear soil properties in situ using a noninvasive field technique.

Subsurface interpretation of paleokarst reservoirs is greatly aided by 3D seismic and other modern modeling tools and the inherent complexity of productive reservoirs requires an understanding of reservoir heterogeneities and compartmentalization. Such complexity also requires a review of karst processes and development, which can be beneficially captured via geophysical characterization of near-surface karst landscape features that certainly equate to our better understanding of high-side oil productive areas. Both electrical resistivity tomography (ERT) and refraction microtremor (ReMi) geophysical surveys at the Green River Preserve adjacent to Mammoth Cave National Park in the Mississippian Ste. Genevieve and Girkin Limestones are providing details of karst features, including horizontal passages, uvulas or karst valleys, sinkholes (dolines), vertical pits or dome caves, and associated karst system infill. Geophysical anomalies include reversals of shearwave velocities in a domal (pit) cave, and an inferred bedding-plane controlled conduit system associated with a drained sinkhole basin. Other anomalies detected in the shallow subsurface include large contrasts in geoelectrical measurements near the sinkhole basin interpreted also as a cave or conduit system. In contrast to anomalies, a mappable continuity of ERT and ReMi transects along the Green River suggests bedrock joints controlling the linear nature of bedrock highs and lows, similar to a series of grikes and clints that typify the south-central Kentucky karst.

A 3 ton (2.7 metric tonnes [t]), granitoid lonestone with Appalachian provenance was found in situ in offshore Devonian black shale in northeastern Kentucky, United States, and is denoted herein as the Robinson boulder, or lonestone, after its discoverer, Michael J. Robinson. This large boulder appears to have been displaced nearly 500 km from its source on the opposite margin of the Acadian/Neoacadian Appalachian foreland basin. While previous identifications of possible lonestones have been attributed to Pleistocene glacial events, scrutiny of this lonestone’s origin suggests that the boulder, which was embedded in the Upper Devonian Cleveland Shale Member of the Ohio Shale in northeastern Kentucky, is most likely a Devonian ice-rafted glacial dropstone. Notably, palynologic correlation with reported glacial diamictites elsewhere in the basin indicates such a source. Together, the dropstone and diamictites, separated by ~500 km, provide evidence for alpine glaciation in the ancient Acadian/Neoacadian orogen and for tidewater glaciers in the adjacent, eastern margin of the foreland basin. The latest Devonian marine transgression and Neoacadian foreland subsidence are interpreted to have been associated with tidewater glacial connections to the open sea. Importantly, the existence of this dropstone and its likely glacial precursor events require new considerations about contemporary black-shale sedimentation and the influence of tectonics on the delivery of glacial sediments to foreland basins.

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for 5 years in the areas of MEMS, nanotechnology and advanced materials. He has served as a guest editor/editorial board of journals including Journals of Materials Science. Dr. Allameh holds a PhD from The Ohio State University. He has published over 70 scientific papers/book chapters.