S U M M A R Y We present a statistical analysis of focal mechanism orientations for nine California fault zones with the goal of quantifying variations of fault zone heterogeneity at seismogenic depths. The focal mechanism data are generated from first motion polarities for earthquakes in the time period 1983–2004, magnitude range 0–5, and depth range 0–15 km. Only mechanisms with good quality ...

To determine factors controlling permeability variations within and adjacent to a fault-hosted geothermal reservoir at Dixie Valley, Nevada, we conducted borehole televiewer observations of wellbore failure (breakouts and cooling cracks) together with hydraulic fracturing stress measurements in six wells drilled into the Stillwater fault zone at depths of 2-3 km. Measurements in highly permeabl...

Low-temperature chronometers offer potential to gain insights into the temporal evolution of hydrothermal systems. The long-lived fault-bound Grimsel pass system (including a fossil and an active part) in Central European Alps serves here as key site test such application. Zircon apatite grains were separated from samples collected along fault transect. resulting zircon (U-Th)/He ages are homog...

Abstract Although the Wasatch fault is currently known to have a high-seismic hazard from motion along range-bounding faults, new seismic data reveal faulted and folded 13,000–30,000-yr-old Lake Bonneville strata beneath Salt City (SLC). Coupled with previous excavation trench, borehole, other geologic geophysical observations, we conclude that zone of latest Pleistocene and/or Holocene faultin...

We deployed a dense linear array of 45 seismometers across and along the San Andreas fault near Parkfield a week after the M 6.0 Parkfield earthquake on 28 September 2004 to record fault-zone seismic waves generated by aftershocks and explosions. Seismic stations and explosions were co-sited with our previous experiment conducted in 2002. The data from repeated shots detonated in the fall of 20...

Fault zones are thought to consist of regions with reduced seismic velocity. When sources are located in or close to these low-velocity zones, guided seismic head and trapped waves are generated which may be indicative of the structure of fault zones at depth. Observations above several fault zones suggest that they are common features of near fault radiation, yet their interpretation may be hi...