Numerical modeling of strike-slip creeping faults and implications for the Hayward fault, California
38
Citation
32
Reference
10
Related Paper
Citation Trend
Keywords:
Elastic-rebound theory
Elastic-rebound theory
Stress field
Displacement field
Cite
Citations (3)
Some of the fault slip associated with the 1979 Imperial Valley
earthquake occurred along other than the Imperial fault and the
Brawley fault zone. More than 90 km to the north of the seismogenic
fault, a 39-km-long section of the San Andreas fault developed a
discontinuous set of surficial fractures soon after the earthquake. This
set of fractures consisted of small left-stepping echelon cracks displaying
extensional and dextral components of movement. Average dextral
slip was about 4 mm, and slip reached 10 mm at one point along
the fault. In one locality the cracks formed between Va and 4Vfe days
after the main shock, although slippage at depth may have been
nearly simultaneous with the earthquake.
In general, this set of breaks duplicates the location, style, and slip
magnitude of the set that was mapped in 1968 after the Borrego
Mountain, Calif, earthquake. Such near-duplication indicates that
this section of the San Andreas fault, in particular, is susceptible to
small amounts of triggered slip. Although the reasons for such behavior
are far from clear, similar behavior of the Imperial fault before
1979 suggests that this section of the San Andreas fault may generate
a moderate earthquake within the next few decades.
Elastic-rebound theory
Transform fault
Cite
Citations (15)
A vertical strike slip fault, situated in VISCO-elastic layer, representing the lithosphere is considered. The upper part of the fault is assumed to remain locked, except during an earthquake, when it slips. It is assumed that the lower parts of the fault slip past each other. It is also assumed that tectonic forces maintain a shear stress far away from the fault. Exact solutions are obtained for the displacements and stresses in the system and it is shown that gradual accumulation of shear stress would occur in the neighborhood of the fault. There would be considerable amplification of shear stress on the locked part of the fault, leading finally to a sudden slip of the upper part of the fault under suitable circumstances. The mathematical results are compared with some relevant observations on the surface deformations in the neighborhood of strike-slip faults. It is shown that such comparison can be used to obtain estimates of the probable time of sudden fault slip, if sufficient data are available, and would also lead to estimates of the ratio of the effective viscosity of the lithosphere in the neighborhood of the fault and the shear stress maintained by tectonic forces far away from the fault. It is also shown that the results are likely to be useful in obtaining greater insight into the problem of earthquake prediction and in estimating the changes of seismic risk with time near an active fault.
Elastic-rebound theory
Cite
Citations (0)
Earthquake recurrence data from the Pallett Creek and Wrightwood paleoseismic sites on the San Andreas fault appear to show temporal variations in repeat interval. These sites are located near Cajon Pass, southern California, where detailed mapping has revealed geomorphically and structurally expressed domains of alternating extension and contraction respectively associated with releasing and restraining bends of the San Andreas fault. We investigate the interaction between strike‐slip faults and auxiliary reverse and normal faults as a physical mechanism capable of producing such variations. Under the assumption that fault strength is a function of fault‐normal stress (e.g. Byerlee's Law), failure of an auxiliary fault modifies the strength of the strike‐slip fault, thereby modulating the recurrence interval for earthquakes. In our finite element model, auxiliary faults are driven by stress accumulation near restraining and releasing bends of a strike‐slip fault. Earthquakes occur when fault strength is exceeded and are incorporated as a stress drop which is dependent on fault‐normal stress. The model is driven by a velocity boundary condition over many earthquake cycles. Resulting synthetic strike‐slip earthquake recurrence data display temporal variations similar to observed paleoseismic data within time windows surrounding auxiliary fault failures. Although observed recurrence data for the two paleoseismic sites are too short to be definitive about the temporal variations or the physical mechanism responsible for it, our simple model supports the idea that interaction between a strike‐slip fault and auxiliary reverse or normal faults can modulate the recurrence interval of events on the strike‐slip fault, possibly producing short term variations in earthquake recurrence interval.
Elastic-rebound theory
Cite
Citations (9)
Earthquake hazard assessments rely on observations from the field and geophysical data that provide fault slip rate estimates at specific sites and inform the geometry of active faults; however, uncertainty remains for both slip rate and geometry. Furthermore, incompatibilities between inferred fault geometry and geologic slip rates arise within crustal deformation models where model and geologic slip rates disagree. The impact of these incompatibilities may be local to sites or have wider effect on the fault system deformation. Here, we investigate the roles of structural position of sites and uncertainty of slip rates using three-dimensional mechanical models that simulate deformation across many earthquake cycles along southern San Andreas fault near the San Gorgonio Pass in California. Within the models, the impact of strike-slip rate sites on the fault system depends on their structural positions. Slip rates at sites along short and segmented faults has lesser impact on the slip along the fault system than either slip rates at sites along longer faults or at sites within fault branches. Consequently, inaccuracies in the slip rate estimates used for seismic hazard assessment may have differing impacts on the fault system depending on location and structural position of the slip rates. Fault branches along strike-slip faults warrant detailed investigation not only because these areas have high spatial variability of slip rate and accrue nearby off-fault deformation but also because changes in slip rates along branches has larger impact on deformation along fault system than other sites. Lack of data or large uncertainty in slip rate data from fault branches can affect our ability to accurately assess seismic hazard of the region.
Elastic-rebound theory
Cite
Citations (2)
Abstract The spacing of parallel continental strike‐slip faults can constrain the mechanical properties of the faults and fault‐bounded crust. In the western US , evenly spaced strike‐slip fault domains are observed in the San Andreas ( SA ) and Walker Lane ( WL ) fault systems. Comparison of fault spacing ( S ) vs. seismogenic zone thickness ( L ) relationships of the SA and WL systems indicates that the SA has a higher S / L ratio (~8 vs. 1, respectively). If a stress‐shadow mechanism guides parallel fault formation, the S / L ratio should be controlled by fault strength, crustal strength, and/or regional stress. This suggests that the SA ‐related strike‐slip faults are relatively weaker, with lower fault friction: 0.13–0.19 for the SA vs. 0.20 for WL . The observed mechanical differences between the San Andreas and Walker Lane fault systems may be attributed to variations in the local geology of the fault‐hosting crust and/or the regional boundary conditions (e.g. geothermal gradient or strain rate).
Elastic-rebound theory
Cite
Citations (12)
article i nfo The ENE striking Altyn-Tagh Fault and the WNW striking Karakax Fault are two major strike-slip fault sys- tems in northern Tibet, and form a prominent ~2000 km long fault system. The 2008 Yutian normal faulting earthquake (Mw 7.1) struck near the southern edge of the Tarim Basin, where the two fault systems con- verge. While there are numerous NS-trending normal faults particularly in southern Tibet, their tectonic or- igins have remained contentious. Based on crustal deformation data sets obtained from synthetic aperture radar (SAR) as well as aftershock distribution, we developed a non-planar fault source model for the 2008 Yutian earthquake that exhibits a large normal-fault slip on a west-dipping surface with a nearly NS strike, thus suggesting a localized EW trending extensional stress field. The extensional stress was presumably gen- erated at a step-over region of two NE-trending left-lateral strike-slip faults, which would probably belong to the Altyn-Tagh and Longmu-Gozha Co Fault Systems. In the epicentral area, there exists a fault scarp that co- incides with the top edge of our fault model, and thus similar earthquakes must have occurred over geolog- ical time. Such normal faulting earthquakes must have been repeatedly suppressed the left-lateral slip behavior of the Karakax Fault. In addition, if the slip along the Altyn-Tagh Fault is transferred to the Longmu-Gozha Co Fault, which is SE across the normal fault system, the slip rate of the Karakax Fault would be less than that of the adjoining Altyn-Tagh Fault.
Elastic-rebound theory
Stress field
Cite
Citations (0)
Thrust fault
Elastic-rebound theory
Transform fault
Echelon formation
Cite
Citations (93)