Abstract:We present an underground cosmic ray muon tomographic experiment imaging 3D density of overburden, part of a joint study with differential gravity. Muon data were acquired at four locations within a tunnel beneath Los Alamos, New Mexico, and used in a 3D tomographic inversion to recover the spatial variation in the overlying rock-air interface, and compared with a priori knowledge of the topography. Densities obtained exhibit good agreement with preliminary results of the gravity modeling, which will be presented elsewhere, and are compatible with values reported in the literature. The modeled rock-air interface matches that obtained from LIDAR within 4 m, our resolution, over much of the model volume. This experiment demonstrates the power of cosmic ray muons to image shallow geological targets using underground detectors, whose development as borehole devices will be an important new direction of passive geophysical imaging.One Sentence Summary: 3D density modeling using an underground cosmic ray muon detector points the way to new borehole methods for passive shallow geophysical imaging.

The seismically active Pajarito fault system (PFS) of northern New Mexico, UnitedStates, is a complex zone of deformation made up of many laterally discontinuous faults and associated folds and fractures that interact in ways that have important implications for seismic hazards. Mapping and drilling projects in the PFS provide new insights into the structural geometry and paleoseismic history of the fault system. A 1.25 Ma old datum (the Bandelier Tuff) and high-resolution digital elevation data allow construction of throwlength profi les along the entire length of the PFS, revealing primary geometric features previously unrecognized. The fault system as a whole consists of numerous closely spaced overlapping sections ~8-14 km long. Slip maxima in some cases occur near the centers of these sections, and in others they are shifted toward one end. Along-strike asymmetrical throw profi les and throw defi cits indicate fault branching, merging, and strain transfer. This pattern results from processes of fault linkage and conservation of strain on diverse structures of a large fault system. New mapping reveals that the northern end of the Pajarito fault terminates in a wide zone of extensional monoclines and discontinuous, small-displacement faults, and interacts with nearby antithetic faults. New paleoseismic data from a normal fault splay, interpreted in light of previous paleoseismic work, argue for three Holocene surface-rupturing earthquakes; one ca. 1.4 thousand calendar years ago (1.4 cal ka) on the Pajarito fault, a second 6.5-5.2 ka ago on the Pajarito fault that is consistent with an event 6.5-4.2 ka ago on the Guaje Mountain fault, and a third ca. 9 ka ago on both the Pajarito and the Rendija Canyon faults. This paleoseismic event chronology demonstrates that the Pajarito fault often ruptures alone, but sometimes ruptures either with the Rendija Canyon or the Guaje Mountain fault. When this occurs, the resultant seismic moment and therefore the earthquake magnitude are larger than when the main Pajarito fault ruptures alone. Evidence for fault interaction, and the presence of prominent bends in the Pajarito fault system, imply structural control of paleoseismicity and neoseismicity and suggest the potential for stress concentrations and earthquake triggering in complex linking fault systems. on 23 July 2009 geosphere.gsapubs.org Downloaded from Fault interaction and variation in throw in the Pajarito fault systemGeosphere,

Abstract-Efficient detection and high-fidelity quantification of surface changes resulting from underground activities are important national and global security efforts. In this investigation, a team performed field-based topographic characterization by gathering high-quality photographs at very low altitudes from an unmanned aerial system (UAS)-borne camera platform. The data collection occurred shortly before and after a controlled underground chemical explosion as part of the United States Department of Energy's Source Physics Experiments (SPE-5) series. The highresolution overlapping photographs were used to create 3D photogrammetric models of the site, which then served to map changes in the landscape down to 1-cm-scale. Separate models were created for two areas, herein referred to as the test table grid region and the nearfield grid region. The test table grid includes the region within *40 m from surface ground zero, with photographs collected at a flight altitude of 8.5 m above ground level (AGL). The near-field grid area covered a broader area, 90-130 m from surface ground zero, and collected at a flight altitude of 22 m AGL. The photographs, processed using Agisoft Photoscan Ò in conjunction with 125 surveyed ground control point targets, yielded a 6-mm pixelsize digital elevation model (DEM) for the test table grid region. This provided the B3 cm resolution in the topographic data to map in fine detail a suite of features related to the underground explosion: uplift, subsidence, surface fractures, and morphological change detection. The near-field grid region data collection resulted in a 2-cm pixel-size DEM, enabling mapping of a broader range of features related to the explosion, including: uplift and subsidence, rock fall, and slope sloughing. This study represents one of the first works to constrain, both temporally and spatially, explosion-related surface damage using a UAS photogrammetric platform; these data will help to advance the science of underground explosion detection.

Summary Wildfires are a global crisis, but current fire models fail to capture vegetation response to changing climate. With drought and elevated temperature increasing the importance of vegetation dynamics to fire behavior, and the advent of next generation models capable of capturing increasingly complex physical processes, we provide a renewed focus on representation of woody vegetation in fire models. Currently, the most advanced representations of fire behavior and biophysical fire effects are found in distinct classes of fine‐scale models and do not capture variation in live fuel (i.e. living plant) properties. We demonstrate that plant water and carbon dynamics, which influence combustion and heat transfer into the plant and often dictate plant survival, provide the mechanistic linkage between fire behavior and effects. Our conceptual framework linking remotely sensed estimates of plant water and carbon to fine‐scale models of fire behavior and effects could be a critical first step toward improving the fidelity of the coarse scale models that are now relied upon for global fire forecasting. This process‐based approach will be essential to capturing the influence of physiological responses to drought and warming on live fuel conditions, strengthening the science needed to guide fire managers in an uncertain future.

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