Thesis (doctoral)--Universität Potsdam, 2004. / "September 2004"--P. [2] of cover. Vita. Includes bibliographical references (p. [115]-132). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Four folded plates in pocket. Includes bibliographical references (leaves 285-303). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph.D.)--Memorial University of Newfoundland, 1996. / Restricted until November 1997. Bibliography: leaves 228-255. Also available online.

The spatial patterns of bimaterial interfaces along the Parkfield section of the San Andreas Fault (SAF) and central section of the Calaveras Fault are systematically investigated with large data sets of near-fault waveforms. Different from the usage of direct P and S waves in traditional tomographic studies, a particular seismic phase named fault zone head wave (FZHW) is used to image the bimaterial fault interfaces. The results show clear variations of seismic velocities contrast both along-strike and along-depth directions in both regions, which is in general consistent with local geological setting at surface and existing 3D tomography results. In the Parkfield section of SAF, the result of velocity contrast is used to test the relationship between preferred rupture directions of M6 Parkfield earthquakes and bimaterial interface. Strong velocity contrast (~5-10%) near Middle Mountain (MM) could control the rupture directions of nearby earthquakes to SE, such as the case for 1966 M6 Parkfield earthquake. In comparison, weak velocity contrast (~0-2%) near the epicenter of the 2004 Parkfield M6 earthquake (i.e., Gold Hill) probably has no influence on controlling its rupture direction, which is consistent with the bilateral rupture of the 2004 Parkfield earthquake. In the central Calaveras Fault, a detailed analysis of the moveout between FZHWs and direct P waves revealed the existence of a complicated fault structure with velocity contrast increasing from NW to SE of station CCO. The high velocity contrast SE of station CCO could be caused by a low-velocity zone SE of station CCO. The spatio-temporal variations of seismic velocity around the central Calaveras Fault and its nearby region are investigated based on the waveform analysis of 333 repeating clusters following the 1984 ML6.2 Morgan Hill earthquake. Clear reduction of seismic velocity is shown for all repeating clusters immediately after the mainshock, followed by a logarithmic recovery. The coseismic change mostly occurs at shallow layers (top few hundred meters) for the region away from the rupture area of the mainshock, but extends much deeper around the rupture zone of the Morgan Hill earthquake. The estimated depth of the damage zone is up to 6 km in the fault based on the repeating clusters directly beneath station CCO. Finally, temporal changes around the Parkfield section of SAF are studied using recently developed ambient noise cross-correlation technique. The extracted daily empirical Green functions (EGFs) from 0.4-1.3 Hz noise records are used to estimate subtle temporal changes associated with large earthquakes from local to teleseismic distances. The results show clear coseismic reduction of seismic velocities after the 2004 M6 Parkfield earthquake, similar to the previous observation based on repeating earthquakes. However, no systematic changes have been detected for other four regional/teleseismic events that have triggered clear tremor activity in the same region. These results suggest that temporal changes associated with distance sources are very subtle or localized so that they could not be detected within the resolution of the current technique (~0.2%).

The Valle de Catacamas forms a major basin along the central portion of the Guayape fault, the most prominent tectonic element of the Chortís block. The Guayape fault extends 290 km southwest from the Caribbean coast to the region of El Paraíso, Honduras, and may continue to the Pacific coast along a related prominent topographic feature, the Choluteca linear. Basins presently forming along the Guayape fault indicate that the fault is currently experiencing right-slip. The active features of the Valle de Catacamas displace older folds and reverse faults which apparently formed during an earlier period of sinistral shear. Thus, the Guayape fault has undergone at least two phases of movement, post-Cenomanian left-slip followed by the present right-slip. The geology of the valley suggests multiple stages of evolution. These include at least one period of thrust and reverse faulting, possibly associated with sinistral shear along the Guayape fault, and a recent episode of normal faulting associated with dextral shear on the Guayape fault. Thrusting of basement rocks over Jurassic strata on the south side of the valley was the earliest deformation to affect Mesozoic or Cenozoic rocks. The event can only be dated as post-Jurassic in age. The Cretaceous rocks of the Sierra de Agalta on the north side of the Valle de Catacamas are much more strongly deformed than similar rocks in central Honduras. In this range, the Aptian-Albian Atima Limestone commonly has a pervasive pressure solution cleavage which has not been reported from other locations on the Chortís block. The cleavage is apparently axial planar to the folds. The age of this deformation is constrained only as post-Cenomanian. SIR data indicate that these folds are deflected in sinistral shear near the Guayape fault. In addition, a major structural contact has a large left-lateral separation. The folds in the Sierra de Agalta are cut by the range-bounding normal fault of the Sierra de Agalta. Younger rocks are placed on older rocks by this normal fault, and fault slip data from small fault planes in the footwall block indicate normal faulting. The N 65° E strike of this normal fault, the N 35° E strike of the Guayape fault, and stress orientations inferred from fault slip data indicate that the present movement on the Guayape fault is right-slip. Fault slip data from the Guayape fault zone is heterogeneous as would be expected if two stage slip has occurred. / text