2004/12/01 by James N. Brune · 12 citations
Earth and Planetary Sciences · Engineering · Environmental Science · #earthquake and tectonic studies #Seismic Performance and Analysis #Landslides and related hazards #Geology #Seismology #Thrust fault #Structural basin #Thrust #Fault (geology) #Geomorphology #Engineering
paper · doi:10.1785/0120030252
published in Bulletin of the Seismological Society of America 94(6), 1993-2003 (Seismological Society of America)
openalex publication_date 2004/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/04/04
Abstract Precariously balanced rocks and overturned transformers in the vicinity of the White Wolf fault provide constraints on ground motion during the 1952 Ms 7.7 Kern County earthquake, a possible analog for an anticipated large earthquake in the Los Angeles basin (Shaw et al., 2002; Dolan et al., 2003). On the northeast part of the fault preliminary estimates of ground motion on the footwall give peak accelerations considerably lower than predicted by standard regression curves. On the other hand, on the hanging-wall, there is evidence of intense ground shattering and lack of precarious rocks, consistent with the intense hanging-wall accelerations suggested by foam-rubber modeling, numerical modeling, and observations from previous thrust fault earthquakes. There is clear evidence of the effects of rupture directivity in ground motions on the hanging-wall side of the fault (from both pre-carious rocks and numerical simulations). On the southwest part of the fault, which is covered by sediments, the thrust fault did not reach the surface (“blind ” thrust). Overturned and damaged transformers indicate significant transfer of energy from the hanging wall to the footwall, an effect that may not be as effective when the rupture reaches the surface (is not “blind”). Transformers near the up-dip projection of the fault tip have been damaged or over-turned on both the hanging-wall and footwall sides of the fault. The transfer of energy is confirmed in a numerical lattice model and could play an important role in a similar situation in Los Angeles. We suggest that the results of this study can provide im-portant information for estimating the effects of a large thrust fault rupture in the Los Angeles basin, specially given the fact that there is so little instrumental data from large thrust fault earthquakes.