[Group A | Group B | Group C | Group E | Group F]

Research topics of interest to Group D for 2000 are:

Task D1: LARSE. The main part of the LARSE II experiment was done in October, 1999. The data from this portion of the experiment is being downloaded from the instruments and will be put into a common format. We expect the data to be ready for scientific users by February 1, 2000, and will be distributed by the data center. Data from the passive experiment is currently being submitted to the IRIS-DMC. We hope to have a few preview plots of the data available on the Data Center in December (check the home page of the Data Center). Access to the data from the LARSE II experiments will be restricted for two years to scientists who actively participated in the LARSE survey (as per NSF guidelines). The high resolution part of the survey has been delayed until 2000. Proposed research on LARSE should focus on basin, crustal and mantle structure derived from the new data.

Task D2: SCEC 3D Seismic Velocity Model. The outline of the Version 2 of the SCEC 3D Seismic Velocity Model was presented at the Palm Springs meeting and will be released in January, 2000. This version will have a tomographically derived background velocity, a top geotechnical layer, and laterally varying Moho depth, and an Imperial Valley structure. Proposals should address improvements and testing of the model. TriNet Data from the Hector Mines earthquake should allow for a better determination of the low-frequency response of the basins. Proposals to re-locate the entire seismicity catalog, compute travel time tables, compare waveform modeling to observed seismograms, and check the model against station terms are encouraged. In the coming year, we plan to develop Version 3 of the velocity model that will incorporate more lateral variations in the crust and upper mantle as well as better calibration of the basin structure to borehole and gravity data.

Task D3: Fault Zone Trapped Wave Studies. Research in this area has the goal of determining physical properties, spatial continuity and temporal healing of the fault zone from waves trapped in the zone itself. Important problems to pursue include deciphering depth- dependence and segmentation of the fault zone waveguide, and its rate of healing following large earthquakes. Priority will be given to studies with resolution of these properties at seismogenic depths. The Hector Mines earthquake provided a new opportunity to observe the trapped waves. These data will be available in early 2000.

Task D4: Stress Measurements. We are interested in research related to the determination of in situ stress. Two methods have be proposed to do this -- stress measured from earthquakes and stress inferred from bore-hole breakouts.

Task D5: Seismicity. We desire a catalog of all events relocated with the Version 2 of the standard velocity model. This catalog would be made available through the Data Center. We also seek a standard catalog of focal-mechanism and/or moment tensor source characterizations. Also, the regionalized maximum depth of earthquakes and the reasons for this, is another topic of interest.

Task D6: Lower-Crust and Upper Mantle Properties. To help provide a tectonic framework for earthquake processes, we are interested in the properties in the upper mantle and lower-crust beneath S. California. In particular, mantle tomographic studies, studies of shear- wave splitting (indicating subducted slab orientation), receiver functions, and surface wavedispersion are of interest.

Task D7: Tectonic Modeling. We seek proposals to study the physical forces driving fault slip and geodetic displacements. Group D will focus on studies that primarily employ measurements of physical properties, such as those employing seismic and gravity data. Those based primarily on geodetic data should be addressed to Group E, while integrative studies or those employing numerous data types should be addressed to Group A.

Task D8: Three-dimensional structural model of southern California. As part of its legacy document, SCEC wishes to develop the best up-to-date 3-D fault and geology model of the crust in southern California. Surface topography (DEM) should be included. Ideally the model should be web-based and use visualization software to view the model from different directions. The model may be broken down by seismotectonic province in order to improve the on-screen resolution. See also Task C5.