Contemporary in situ tectonic stress indicators along the San Andreas fault system in central California show northeast-directed horizontal compression that is nearly perpendicular to the strike of the fault. Such compression explains recent uplift of the Coast Ranges and the numerous active reverse faults and folds that trend nearly parallel to the San Andreas and that are otherwise unexplainable in terms of strike-slip deformation. Fault-normal crustal compression in central California is proposed to result from the extremely low shear strength of the San Andreas and the slightly convergent relative motion between the Pacific and North American plates. Preliminary in situ stress data from the Cajon Pass scientific drill hole (located 3.6 kilometers northeast of the San Andreas in southern California near San Bernardino, California) are also consistent with a weak fault, as they show no right-lateral shear stress at approximately 2-kilometer depth on planes parallel to the San Andreas fault.

In June 2009, the New York Times published an article about the public fear of geothermal development causing earthquakes. The article highlighted a project funded by the U.S. Department of Energy's (DOE) Geothermal Technologies Program bringing power production at The Geysers back up to capacity using Enhanced Geothermal Systems (EGS) technology. The Geysers geothermal field is located two hours north of San Francisco, California, and therefore, the article drew comparisons to a similar geothermal EGS project in Basel, Switzerland believed to cause a magnitude 3.4 earthquake. In order to address public concern and gain acceptance from the general public and policymakers for geothermal energy development, specifically EGS, the U.S. Department of Energy commissioned a group of experts in induced seismicity, geothermal power development and risk assessment to write a revised Induced Seismicity Protocol. The authors met with the domestic and international scientific community, policymakers, and other stakeholders to gain their perspectives and incorporate them into the Protocol. They also incorporated the lessons learned from Basel, Switzerland and other EGS projects around the world to better understand the issues associated with induced seismicity in EGS projects. The Protocol concludes that with proper study and technology development induced seismicity will not only be mitigated, but will become a useful tool for reservoir management. This Protocol is a living guidance document for geothermal developers, public officials, regulators and the general public that provides a set of general guidelines detailing useful steps to evaluate and manage the effects of induced seismicity related to EGS projects. This Protocol puts high importance on safety while allowing geothermal technology to move forward in a cost effective manner. The goal of this Protocol is to help facilitate the successful deployment of EGS projects, thus increasing the availability of clean, renewable and domestic energy in the United States. Project developers should work closely with the National Environmental Policy Act (NEPA) compliance officials of the involved Federal agency(ies) to align information needs and public involvement activities with the NEPA review process. The authors emphasize this Protocol is neither a substitute nor a panacea for regulatory requirements that may be imposed by federal, state or local regulators. I would like to acknowledge everyone who gave their time and expertise at the induced seismicity workshops (see Appendix D) that led to this updated Protocol. Their input was critical to develop an informed and useful document. In addition, I would like to thank the authors of this document, whose ideas and support came together to write a clear and concise Protocol. This document was put out for public comment and reviewed by NEPA, the U.S. Department of Energy and General Counsel. Special thanks to Christy King-Gilmore and Brian Costner for their guidance.

The number of strong ground motion recordings available for regression analysis in developing empirical attenuation relationships has rapidly grown in the last 10 years. However, the dearth of strong-motion data from the Cascadia subduction zone has limited this development of relationships for the Cascadia subduction zone megathrust, which can be used in the calculation of design spectra for engineered structures. A stochastic finite-fault ground-motion model has been used to simulate ground motions for moment magnitude (M) 8.0, 8.5, and 9.0 megathrust earthquakes along the Cascadia subduction zone for both rock-and soil-site conditions. The stochastic finite-fault model was validated against the 1985 M 8.0 Michoacan, Mexico, and the 1985 M 8.0 Valpariso, Chile, earthquakes. These two subduction zone megathrust earthquakes were recorded at several rock sites located near the fault rupture. For the Cascadia megathrust earthquakes, three different rupture geometries were used to model the M 8.0, 8.5, and 9.0 events. The geometries only differ in their respective fault lengths. A fault dip of 9Њ to the east with a rupture width of 90 km was selected to represent average properties of the Cascadia subduction zone geometry. A regional crustal damping and velocity model was used with the stochastic finite-fault model simulations. Ground motions were computed for 16 site locations. The parametric uncertainties associated with the variation in source, path, and site effects were included in the development of the ground motions. A functional form was fit to the ground-motion model simulations to develop regionspecific attenuation relationships for the Cascadia megathrust rupture zone for both rock and soil site conditions. The total uncertainty was based on a combination of the modeling and parametric uncertainties (sigmas). These newly developed attenuation relationships for Cascadia subduction zone megathrust earthquakes can be used in both the probabilistic and deterministic seismic-hazard studies for engineering design for the Pacific Northwest.

Goldfinger et al. (2012) interpreted a 10,000 year old sequence of deep sea turbidites at the Cascadia subduction zone (CSZ) as a record of clusters of plate-boundary great earthquakes separated by gaps of many hundreds of years. We performed statistical analyses on this inferred earthquake record to test the temporal clustering model and to calculate time-dependent recurrence intervals and probabilities. We used a Monte Carlo simulation to determine if the turbidite recurrence intervals follow an exponential distribution consistent with a Poisson (memoryless) process. The latter was rejected at a statistical significance level of 0.05. We performed a cluster analysis on 20 randomly simulated catalogs of 18 events (event T2 excluded), using ages with uncertainties from the turbidite dataset. Results indicate that 13 catalogs exhibit statistically significant clustering behavior, yielding a probability of clustering of 13=20 or 0.65. Most (70%) of the 20 catalogs contain two or three closed clusters (a sequence that contains the same or nearly the same number of events) and the current cluster T1-T5 appears consistently in all catalogs. Analysis of the 13 catalogs that manifest clustering indicates that the probability that at least one more event will occur in the current cluster is 0.82. Given that the current cluster may not be closed yet, the probabilities of an M 9 earthquake during the next 50 and 100 years were estimated to be 0.17 and 0.25, respectively. We also analyzed the sensitivity of results to including event T2, whose status as a full-length rupture event is in doubt. The inclusion of T2 did not change the probability of clustering behavior in the CSZ turbidite data, but did significantly reduce the probability that the current cluster would extend to one more event. Based on the statistical analysis, time-independent and time-dependent recurrence intervals were calculated. BSSA Early Edition / 1

Probabilistic seismic hazard analyses were conducted to estimate both ground motion and fault displacement hazards at the potential geologic repository for spent nuclear fuel and high-level radioactive waste at Yucca Mountain, Nevada. The study is believed to be the largest and most comprehensive analyses ever conducted for ground-shaking hazard and is a first-of-a-kind assessment of probabilistic fault displacement hazard. The major emphasis of the study was on the quantification of epistemic uncertainty. Six teams of three experts performed seismic source and fault displacement evaluations, and seven individual experts provided ground motion evaluations. State-of-the-practice expert elicitation processes involving structured workshops, consensus identification of parameters and issues to be evaluated, common sharing of data and information, and open exchanges about the basis for preliminary interpretations were implemented. Ground-shaking hazard was computed for a hypothetical rock outcrop at -300 m, the depth of the potential waste emplacement drifts, at the designated design annual exceedance probabilities of 10-3 and 10-4. The fault displacement hazard was calculated at the design annual exceedance probabilities of 10-4 and 10-5.