[1] Four great earthquakes (1952, 1960, 1964, and 2004) have occurred since seismic monitoring began and only two since the installation of a global seismic network. A reexamination of the 1964 (M 9.2) Prince William Sound (PWS), Alaska, earthquake is timely due to the 2004 Sumatra earthquake because it adds constraints to the potential range of source parameters for these types of infrequent events and aids in the ability to predict the ground motions for other subduction zone including Cascadia. We first measured the durations of high-frequency energy radiation from teleseismic P wave codas recorded by short-period World Wide Standardized Seismographic Network (WWSSN SP) instruments to put constraints on the earthquake rupture length. The durations ranged between 250 and 600 s and are shorter in time between azimuths of 190°and 260°. The fault length is estimated to range from 540 to 740 km, rupturing at average speeds of 1.4-2 km/s in a 220°-238°direction. We developed a multiple time window kinematic rupture model for the PWS earthquake from the least squares inversion of teleseismic P waves, tsunami tide gauge records, and geodetic leveling survey observations based on the Green's function technique. We assume three major fault segments for the subduction zone dipping 6-12°based on geologic data. The subfault size on the megathrust was set to 50 Â 50 km. The Patton Bay fault (PBF) imbricate thrust was assigned a 60 dip with a subfault size of 20 Â 20 km. We estimated a seismic moment of 5.52 Â 10 22 N m (M w 9.12). We identified three areas of major moment release, on the PWS segment near Montague and Middleton Islands extending out to the trench, beneath the Portlock anticline on the Cook segment between 58°N fracture zone and the Kodiak-Bowie seamount chain and finally on the Katmai segment off the coast of Kodiak Island extending to the trench. Our preferred rupture model has a peak slip of 14.9 m along the megathrust and 17.4 m along the PBF. The addition of the PBF resulted in an 8% improvement in residuals and also had a significant effect on the overall slip distribution. Moment release occurred as deep as 50 km depth slab contour near the 350°C isotherm and mantle fore-arc wedge, which is about 10-20 km deeper than previous coupling depths.

The U.S. Bureau of Reclamation's Paradox Valley Unit (PVU) extracts aquifer brine from nine shallow wells along the Dolores River, Paradox Valley, in southwestern Colorado and, after treating, high pressure injects the brine 4.3-4.8 km below the surface. PVU injects at rates between ϳ800 and ϳ1300 L/min. Since 1991, PVU has emplaced over 4 ‫ן‬ 10 6 m 3 of fluid and induced more than 4000 surfacerecorded seismic events. The events are recorded on the local 15-station Paradox Valley Seismic Network. The induced seismicity at Paradox separates into two distinct source zones: a principle zone (Ͼ95% of the events) asymmetrically surrounding the injection well to a maximum radial distance of ϳ3 km, and a secondary, ellipsoidal zone, ϳ2.5 km long and centered ϳ8 km northwest of the injection well. The expansion of these zones has stabilized since mid-1999, about three years after the onset of continuous injection. Within the principal zone, hypocenters align in distinct linear patterns, showing at-depth stratigraphy and the local Wray Mesa fracture and fault system. The primary faults of the Wray Mesa system are aseismic, striking subparallel to the inferred maximum principal stress direction, with one or more faults, probably, acting as fluid conduits to the secondary seismic zone. Individual seismic events, in both zones, do not discernibly correlate with short-term injection parameters; however, a 0.5 km 2 region immediately northwest of the injection well responds to long-term, large-scale changes in injection rate and the surpassing of a threshold injection pressure. Focal mechanisms of the induced events are consistent with simple double-couple, strike-slip moments and subhorizontal extension to the northeast. In addition, the fault planes are consistent with principal stress directions determined from borehole breakouts. More than 99.9% of the PVU seismicity is below human detection (ϳM 2.5). However, approximately 15 events have been felt locally, with the largest being a magnitude M 4.3. Because of the M 4.3 and two earlier-felt M ϳ3.5 events and injection economics, PVU changed injection strategies three times since 1996. These changes reduced seismicity from ϳ1100 events/year to as low as ϳ60 events/year.

It is valuable to construct likelihood functions that rigorously incorporate measurement errors and annual peak discharge, historical, and paleohydrologic bound information in Bayesian flood frequency analyses. Estimates of primary posterior modes for common three‐parameter frequency distributions are constructed using simulated annealing and the simplex method. Parameter and flood frequency probability intervals are calculated directly by systematic parameter space integration. Bayesian flood frequency analyses with annual peak discharge, historical, and paleohydrologic bound data for the Santa Ynez River, California, and the Big Lost River, Idaho, demonstrate that paleohydrologic bounds reduce quantile biases by placing large observed peak discharges in their proper long‐term contexts and substantially narrow peak discharge confidence intervals when estimating floods with low exceedance probabilities.

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