We use data from the 118‐station High Lava Plains (HLP) seismic experiment together with other regional broadband seismic data to image the 3D shear wave velocity structure in the Pacific Northwest using ambient noise tomography. This extensive data set allows us to resolve fine‐scale crustal structures throughout the HLP area in greater detail than previous studies. Our results show 1) a high velocity cylinder in the crust and average velocities in the upper mantle beneath the Owyhee Plateau; 2) a mid‐crustal high velocity anomaly along the Snake River Plain that also extends south into Nevada and Utah; 3) a low velocity anomaly directly beneath Yellowstone throughout the crust; and 4) low velocities beneath the HLP both in the crust and uppermost mantle, possibly indicating very thin or absent mantle lithosphere in the area. These features provide important constraints on possible models for Miocene to recent volcanism in the Pacific Northwest.

[1] We perform a joint inversion of phase velocities from both earthquake and ambient noise induced Rayleigh waves to determine shear wave velocity structure in the crust and upper mantle beneath the Pacific Northwest. We focus particularly on the areas affected by mid-Miocene to present volcanic activity. The joint inversion, combined with the high density seismic network of the High Lava Plains seismic experiment and data from the EarthScope Transportable Array, provides outstanding resolution for this area. In Oregon, we find that the pattern of low velocities in the crust and uppermost mantle varies between the High Lava Plains physiographic province and the adjacent northwestern Basin and Range. These patterns may be due to the presence of the Brothers Fault Zone which separates the clockwise rotating northwest Basin and Range from the relatively undeformed areas further north. Further to the east, the Owyhee Plateau, Snake River Plain (SRP) and northeastern Basin and Range are characterized by high crustal velocities, though the depth extent of these fast wave speeds varies by province. Of particular interest is the mid-crustal high velocity sill, previously only identified within the SRP. We show this anomaly extends significantly further south into Utah and Nevada. We suggest that one possible explanation is lateral crustal extrusion due to the emplacement of the high density mafic mid-crustal sill structures within the SRP.

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Abstract. Fluid injection into geological formations for energy resource development frequently induces (micro)seismicity. If intensely shaking the ground, induced earthquakes may cause injuries and/or economic loss, with the consequence of jeopardizing the operation and future development of these geoenergy projects. To achieve an improved understanding of the causes of induced seismicity, develop forecasting tools, and manage the associated risks, a careful examination of seismic data from reported cases of induced seismicity and the parameters controlling them is necessary. However, these data are hardly gathered together and are time-consuming to collate as they come from different disciplines and sources. Here, we present a publicly available, multi-physical database of injection-induced seismicity (Kivi et al., 2022a; https://doi.org/10.20350/digitalCSIC/14813), sourced from an extensive review of published documents. Currently, it contains 158 datasets of induced seismicity driven by various subsurface energy-related applications worldwide. Each dataset covers a wide range of variables, delineating general site information, host rock properties, in situ geologic and tectonic conditions, fault characteristics, conducted field operations, and recorded seismic activities. We publish the database in flat-file formats (i.e., .xls and .csv tables) to facilitate its dissemination and utilization by geoscientists while keeping it ‎‎directly readable by computer codes for convenient data manipulation. The multi-disciplinary content of this database adds unique value to databases focusing only on seismicity data. In particular, the collected data aims at facilitating the understanding of the spatiotemporal occurrence of induced earthquakes, the diagnosing of potential triggering mechanisms, and the developing of scaling relations of maximum possible earthquake magnitudes and operational parameters. Conclusively, the database will boost research in seismic hazard forecasting and mitigation, paving the way for increasing contributions of geoenergy resources to meeting net-zero carbon emissions.