Publications

Export 4 results:
Sort by: [ Author  (Asc)] Title Type Year
A B C D E F G H I J K L M N O P Q [R] S T U V W X Y Z   [Show ALL]
R
Riedesel, MA, Agnew D, Berger J, Gilbert F.  1980.  Stacking for the frequencies and Qs of 0S0 and 1S0. Geophysical Journal International. 62:457-471.   10.1111/j.1365-246X.1980.tb04867.x   AbstractWebsite

Using nine IDA records for the Indonesian earthquake of 1977 August 19, we have formed an optimal linear combination of the records and have measured the frequency and Q of 0S0 and 1S0. The frequency was measured using the moment ratio method. The attenuation was measured by the minimum width method and by the time-lapse method. The frequency and attenuation were measured simultaneously by varying them to obtain a best fit to the data. A 2000-hr stack, the sum of nine individual records, for 0S0 gave a frequency of 0.814664 mHz±4 ppm. The values for the Q of 0S0 for the three different methods of measurement were 5600,5833 and 5700, respectively. The error in the estimates of Q-1 is about 5 per cent for the minimum power method. For 1S0 a 300-hr stack yielded a frequency of 1.63151 mHz±30 ppm. The values of Q for this mode were 1960, 1800 and 1850, respectively, with an error in Q-1 of about 12 per cent for the minimum power method.

Rojstaczer, S, Agnew DC.  1989.  The Influence of Formation Material Properties on the Response of Water Levels in Wells to Earth Tides and Atmospheric Loading. Journal of Geophysical Research-Solid Earth and Planets. 94:12403-12411.   10.1029/JB094iB09p12403   AbstractWebsite

The water level in an open well can change in response to deformation of the surrounding material, either because of applied strains (tidal or tectonic) or surface loading by atmospheric pressure changes. Under conditions of no vertical fluid flow and negligible well bore storage (static-confined conditions), the sensitivities to these effects depend on the elastic properties and porosity which characterize the surrounding medium. For a poroelastic medium, high sensitivity to applied areal strains occurs for low porosity, while high sensitivity to atmospheric loading occurs for high porosity; both increase with decreasing compressibility of the solid matrix. These material properties also influence vertical fluid flow induced by areally extensive deformation and can be used to define two types of hydraulic diffusivity which govern pressure diffusion, one for applied strain and one for surface loading. The hydraulic diffusivity which governs pressure diffusion in response to surface loading is slightly smaller than that which governs fluid flow in response to applied strain. Given the static-confined response of a water well to atmospheric loading and Earth tides, the in situ drained matrix compressibility and porosity (and hence the one-dimensional specific storage) can be estimated. Analysis of the static-confined response of five wells to atmospheric loading and Earth tides gives generally reasonable estimates for material properties.

Rolandone, F, Burgmann R, Agnew DC, Johanson IA, Templeton DC, d'Alessio MA, Titus SJ, DeMets C, Tikoff B.  2009.  Reply to comment by J. C. Savage on "Aseismic slip and fault-normal strain along the creeping section of the San Andreas Fault''. Geophysical Research Letters. 36   10.1029/2009gl039167   AbstractWebsite
n/a
Rolandone, F, Burgmann R, Agnew DC, Johanson IA, Templeton DC, d'Alessio MA, Titus SJ, DeMets C, Tikoff B.  2008.  Aseismic slip and fault-normal strain along the central creeping section of the San Andreas fault. Geophysical Research Letters. 35   10.1029/2008gl034437   AbstractWebsite

We use GPS data to measure the aseismic slip along the central San Andreas fault (CSAF) and the deformation across adjacent faults. Comparison of EDM and GPS data sets implies that, except for small-scale transients, the fault motion has been steady over the last 40 years. We add 42 new GPS velocities along the CSAF to constrain the regional strain distribution. Shear strain rates are less than 0.083 +/- 0.010 mu strain/yr adjacent to the creeping SAF, with 1 - 4.5 mm/yr of contraction across the Coast Ranges. Dislocation modeling of the data gives a deep, long-term slip rate of 31 - 35 mm/yr and a shallow (0 - 12 km) creep rate of 28 mm/yr along the central portion of the CSAF, consistent with surface creep measurements. The lower shallow slip rate may be due to the effect of partial locking along the CSAF or reflect reduced creep rates late in the earthquake cycle of the adjoining SAF rupture zones.