In order to determine where best to deploy limited resources for mitigating earthquake loss in the US, we need to understand when and where earthquakes may occur and how intense their accelerations can be. Every time an earthquake occurs, we gain more understanding of the earthquake problem through measurements of ground motion and modeling of seismic sources. In addition to information derived from earthquakes, we can also benefit from improved understanding of the seismic source through laboratory measurements and modeling, to anticipate what may occur in future earthquakes. One of the great gaps in our understanding of source processes is how shear resistance varies on a fault during rapid co-seismic slip and what this implies about the magnitudes of stress drops and near-fault accelerations.
In our proposed work plan we will continue our studies on dynamic friction in rocks and analog materials to better understanding thermally-induced slip weakening processes and their consequences for earthquakes, focusing on studies of flash heating/melting at asperity junctions, and fault zone rheological response when there is rapid change in normal stress. We will employ the plate-impact pressure-shear and the modified torsion Kolsky bar experimental configurations. These experimental techniques, developed in our laboratory at CWRU, have been shown by us in pilot experimental studies funded by SCEC, to provide friction data in the slip-speed and normal stress range of relevance to earthquake physics. Besides being useful in the study of dynamic friction at coseismic slip rates, these experimental configurations allow transients, including sudden alterations in both normal stress and shear loading, to be produced to investigate their effects on the fault strength. These studies will be carried out at both room and higher than room test temperatures. The intellectual merit of this proposal is strengthened by the fact that it addresses some of the outstanding problems in earthquake-physics, including the influence of slip, slip velocity, and alterations in normal stress on fault strength during a typical fault rupture process.
The broader aspects of our proposal are strengthened by noting that our proposed research will contribute directly towards reducing losses due to earthquakes in the US in a variety of ways. We will acquire data that are essential for creating realistic models of the earthquake process. Moreover, the proposed program provides exciting opportunities for interdisciplinary research and educational interactions. It involves faculty from two universities?Vikas Prakash from Case School of Engineering, CWRU, and David Goldsby from the Department of Geological Sciences at Brown University. The proposed research program will involve one post-doctoral student and undergraduate students at CWRU. These students will receive valuable and unique interdisciplinary exposure to various aspects of earthquake physics, and will benefit from training in diverse areas such as fault mechanics, fracture mechanics, stress wave propagation, experimental diagnostic techniques, and analytical modeling. The available facilities at CWRU represent the state-of-the-art in high-speed friction testing thereby offering the students involved a unique experimental environment. The University is strongly encouraging the involvement of undergraduate students in cutting edge faculty research, and this would occur for the proposed work as well. Special attention will also be given to recruitment of underrepresented minority students for the project. Dissemination of research results is planned by conference presentations and publications in relevant peer-reviewed journals. Topics in the area of earthquake physics and fault mechanics will undoubtedly enter the departmental seminar series. The PIs will also employ internet and mass-media-based information dissemination to increase awareness of the potential impact of the proposed research in earthquake hazard mitigation. This resource will be available to university level and K-12 students as well as the general public.
