The following list of recently published papers are based on research sponsored by SCEC. These papers are NOT available from SCEC. Most of the journals containing these papers are available at university libraries, and authors may also have reprints of their papers available by request.

If you are looking for technical publications available for puchase, visit our products and publications page.

Other SCEC research papers are listed in an online database.

Recent Research as of 3/22/2002:

(SCEC Contribution numbers are in bold)

507. Li, Y.G., Chester, F.M., and Vidale, J.E., Shallow Seismic Profiling at the Punchbowl Fault Zone, Southern California, Bulletin of the Seismological Society of America, 91, pp. 1820-1830, 2001.

The relationship between seismic velocity and internal fault structure was investigated through a shallow seismic refraction experiment across the exhumed Punchbowl fault, Devil's Punchbowl Los Angeles County Park, California. The Punchbowl fault is a northwest striking, large displacement fault of the San Andreas system that places crystalline basement against arkosic sandstone of the Punchbowl Formation. Seismic refraction profiles using hammer and impulsive shear-wave source along a 300-m-long line reveal the compressional and shear wave structure of the fault zone at shallow depth. Ray tracing with damped least-squaresinversion of travel-times of P and S waves delineate a low-velocity zone centered about the Punchbowl fault. The zone is several tens meters wide with velocities reduced by 10-20 percent relative to the host-rock velocities (Vp = 3.2 km/s for basement and Vp = 2.9 km/s for Punchbowl Formation), with the greatest reduction in the central core of the fault. Thickness of the low velocity zone and the variation in seismic velocity across the zone are qualitatively consistent with expectations based on theobserved distribution of fault-related fracturing and alteration. Apparent crack densities calculated from measured seismic velocities using O'Connell and Budiansky (1974) formulation for a cracked medium range from ~0.4 in the core to a background crack density of 0.1 in the host rock. The variation in calculated crack density across the fault is very similar to observed variations in microfracture density in the Punchbowl Formation sandstone along traverses across the fault. The Poisson's ratio for fault-rock and wall-rock is ~0.25, suggesting that open cracks in the shallow part of the Punchbowl fault zone are dry, consistent with the geologically inferred location of the ground water table. Results of this experiment support the use of seismic methods to image the extent of fault-related fracturing and the geometric complexity of seismic fault zones at depth.

540. Rundle, P.B., J.B. Rundle, K.F. Tiampo, J. Martins, S. McGinnis and W. Klein, Nonlinear Network Dynamics on Earthquake Fault Systems, Physical Review Letters, 87, 14, pp. 148501-1-148501-4, 2001.

Earthquake faults occur in networks that have dynamical modes not displayed by single isolated faults. Using simulations of the network of strike-slip faults in southern California, we find that the physics depends critically on both the interactions among the faults, which are determined by the geometry of the fault network, as well as on the stress dissipation properties of the nonlinear frictional physics, similar to the dynamics of integrate-and-fire neural networks.

550. McClusky, S. C. , S. C. Bjornstad, B. H. Hager, R. W. King, B. J. Meade, M. M. Miller, F. C. Monastero, and B. J. Souter, Present Day Kinematics of the Eastern California Shear Zone from a Geodetically Constrained Block Model, Geophysical Research Letters, 28, pp. 3369-3372, 2001.

We use Global Positioning System (GPS) data from 1993-2000 to determine horizontal velocities of 65 stations in eastern California between 35 ° and 37 \u00b0 N. We relate the geodetic and geologic velocity fields using a block model that enforces path integral constraints and includes the effects of elastic strain accumulation. The velocity of the Sierra Nevada block with respect to Nevada is 11 ± 1 mm/yr, with slip partitioned rather evenly across the Death Valley, (3.5 ± 0.7 mm/yr), Panamint Valley (2.4 ± 1.3 mm/yr), and Airport Lake/Owens Valley (5.3 ± 1.1 mm/yr) faults. The western Mojave block rotates ~2.5¡/Myr clockwise, with 4 ± 2 mm/yr of left lateral motion across the western Garlock Fault. We infer 1 ±2 mm/yr of left lateral motion across the Garlock fault east of the southeast terminus of the Sierra Nevada block, much less than the geologic estimate, consistent with viscoelastic relaxation of a low viscosity lower crust.

557. Kagan, Y. Y., and F. Schoenberg, Estimation of the Upper Cutoff Parameter for the Tapered Pareto Distribution, Journal Appl. Prob., 38A, pp. 158-175, 2001.

The tapered (or generalized) Pareto distribution, also called the modified Gutenberg--Richter law, has been used to model the sizes of earthquakes. Unfortunately, maximum likelihood estimates of the cutoff parameter are substantially biased. Alternative estimates for the cutoff parameter are presented, and their properties discussed.

598. Li, Y.-G. and F. L. Vernon, Characterization of the San Jacinto Fault Zone near Anza, California, from Fault-Zone Trapped Waves, Journal of Geophysical Research, 106, pp. 30676-30688, 2001.

We installed three 350-m-long seismic arrays, each array consisting of 12 three-component stations, across the Coyote Creek fault (CCF), Clark Valley fault (CVF), and Buck Ridge fault (BRF) of the San Jacinto fault zone (SJFZ) in Santa Rosa Mountains southeast of Anza, California. We recorded 4-7 Hz fault-zone trapped waves at stations close to fault traces for microearthquakes occurring within the fault zone. Observations and finite-difference simulations of trapped waves revealed low-velocity and low-Q waveguides on these active faults, in which the shear velocity is reduced by 20- 30% from wall-rock velocities and Q has values of 40-90 in the depth range from the surface to ~18 km. The low-velocity waveguides on these faults are 75 to 100 m wide. Locations of microearthquakes for which we observed trapped waves show that the waveguide on the BRF dips southwestward while the waveguide on the northern CVF dips northeastward. They merge at depth below 12 km and extend northwestward through Anza slip gap connecting to another low-velocity waveguide on the Casa Loma fault (CLF) which has been delineated in our previous study using trapped waves [Li et al., 1997]. However, the waveguide on the CCF along Coyote Creek is nearly vertical and disconnected from the CLF at the south edge of the Anza seismicity gap. We interpret that the low-velocity waveguides inferred from trapped waves on active SJF strands near Anza were the result of recent prehistoric significant earthquakes on them.

643. Yeats, Robert S., Geology of Earthquakes, Encyclopedia of Physical Science and Technology, Third Edition, 6, pp. 649-661, 2002.

List of publications announced 12/18/2001

List of publications announced 9/20/2001

List of publications announced 8/3/2001