Triggering Effect of M 4–5 Earthquakes on the Earthquake Cycle of Repeating Events at Parkfield, California (original) (raw)
Related papers
Spatial-temporal variation of low-frequency earthquake bursts near Parkfield, California
Geophysical Journal International, 2015
Tectonic tremor (TT) and low-frequency earthquakes (LFEs) have been found in the deeper crust of various tectonic environments globally in the last decade. The spatial-temporal behaviour of LFEs provides insight into deep fault zone processes. In this study, we examine recurrence times from a 12-yr catalogue of 88 LFE families with ∼730 000 LFEs in the vicinity of the Parkfield section of the San Andreas Fault (SAF) in central California. We apply an automatic burst detection algorithm to the LFE recurrence times to identify the clustering behaviour of LFEs (LFE bursts) in each family. We find that the burst behaviours in the northern and southern LFE groups differ. Generally, the northern group has longer burst duration but fewer LFEs per burst, while the southern group has shorter burst duration but more LFEs per burst. The southern group LFE bursts are generally more correlated than the northern group, suggesting more coherent deep fault slip and relatively simpler deep fault structure beneath the locked section of SAF. We also found that the 2004 Parkfield earthquake clearly increased the number of LFEs per burst and average burst duration for both the northern and the southern groups, with a relatively larger effect on the northern group. This could be due to the weakness of northern part of the fault, or the northwesterly rupture direction of the Parkfield earthquake.
Bulletin of The Seismological Society of America, 2008
Repeating earthquakes (REs) are sequences of events that have nearly identical waveforms and are interpreted to represent fault asperities driven to failure by loading from aseismic creep on the surrounding fault surface at depth. We investigate the occurrence of these REs along faults in central California to determine which faults exhibit creep and the spatiotemporal distribution of this creep. At the juncture of the San Andreas and southern Calaveras-Paicines faults, both faults as well as a smaller secondary fault, the Quien Sabe fault, are observed to produce REs over the observation period of March 1984 through May 2005. REs in this area reflect a heterogeneous creep distribution along the fault plane with significant variations in time. Cumulative slip over the observation period at individual sequence locations is determined to range from 5.5-58.2 cm on the San Andreas fault, from 4.8-14.1 cm on the southern Calaveras-Paicines fault, and from 4.9-24.8 cm on the Quien Sabe fault. Creep at depth appears to mimic the behaviors seen for creep on the surface in that evidence of steady slip, triggered slip, and episodic slip phenomena are also observed in the RE sequences. For comparison, we investigate the occurrence of REs west of the San Andreas fault within the southern Coast Range. Events within these RE sequences occurred only minutes to weeks apart from each other and then did not repeat again over the observation period, suggesting that REs in this area are not produced by steady aseismic creep of the surrounding fault surface.
Do earthquakes talk to each other? Triggering and interaction of repeating sequences at Parkfield
J. Geophys. Res., 2013
1] Knowledge of what governs the timing of earthquakes is essential to understanding the nature of the earthquake cycle and to determining earthquake hazard, yet the variability and controls of earthquake recurrences are not well established. The large population of small, characteristically repeating earthquakes at Parkfield provides a unique opportunity to study how the interaction of earthquakes affects their recurrence properties. We analyze 112 M À0.4~3.0 repeating earthquake sequences (RESs) to examine the triggering effect from nearby microseismicity. We find that the repeating events with a smaller number of neighboring earthquakes in their immediate vicinity tend to recur in a more periodic manner (i.e., the coefficient of variation in recurrence intervals is less than 0.3). The total static stress perturbation from close-by earthquakes, however, does not seem to strongly influence RES regularity. The uneven distribution of stress changes in time has a modest but significant impact on recurrence intervals. A significant reduction of recurrence intervals occurs in the case of very high-stress changes from neighboring events. Close-by events influence RES timing in a matter of several days or less by short-term triggering. Events that occurred within less than 1 day of an RES often imposed or experienced high-stress changes. A static stress increment of~30 kPa can be enough to produce such short-term triggering. We find that the triggered repeating events are often near the end of their average earthquake cycle, but some events occur following a substantially shortened interval. When comparing the accelerated occurrence at the time of RES events following neighboring events with varying magnitudes, we find that the distance of short-term triggering increases from <1 km to 4 km for M1 to M4 events.
Earthquake recurrence on the southern San Andreas modulated by fault-normal stress
Geophysical Research Letters, 1995
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. Byedee'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.
Tectonophysics, 2006
In this work, we apply the Pattern Informatics technique for evaluating one surface expression of the underlying stress field, the seismicity, in order to study the Parkfield-Coalinga interaction over the years preceding the 1983 Coalinga earthquake. We find that significant anomalous seismicity changes occur during the mid-1970s in this region prior to the Coalinga earthquake that illustrate a reduction in the probability of an event at Parkfield, while the probability of an event at Coalinga is seen to increase. This suggests that the one event did not trigger or hinder the other, rather that the dynamics of the earthquake system are a function of stress field changes on a larger spatial and temporal scale.
M≥7.0 earthquake recurrence on the San Andreas fault from a stress renewal model
[1] Forecasting M ! 7.0 San Andreas fault earthquakes requires an assessment of their expected frequency. I used a three-dimensional finite element model of California to calculate volumetric static stress drops from scenario M ! 7.0 earthquakes on three San Andreas fault sections. The ratio of stress drop to tectonic stressing rate derived from geodetic displacements yielded recovery times at points throughout the model volume. Under a renewal model, stress recovery times on ruptured fault planes can be a proxy for earthquake recurrence. I show curves of magnitude versus stress recovery time for three San Andreas fault sections. When stress recovery times were converted to expected M ! 7.0 earthquake frequencies, they fit Gutenberg-Richter relationships well matched to observed regional rates of M 6.0 earthquakes. Thus a stress-balanced model permits large earthquake Gutenberg-Richter behavior on an individual fault segment, though it does not require it. Modeled slip magnitudes and their expected frequencies were consistent with those observed at the Wrightwood paleoseismic site if strict time predictability does not apply to the San Andreas fault.
2016
We used a comparison of source time function pulse widths to show that a group of earthquakes on the San Andreas fault near Parkfield have a constant duration over a magnitude range of 1.4–3.7. Earthquakes on secondary faults have an increase in duration with magnitude, which is the expected relationship for the usual observation of constant stress drop. The constant duration suggests that fault area is the same regardless of magnitude and that variations in stress drop are due entirely to variations in slip. Calculated stress-drop values on secondary faults range from 0.31 to 14 MPa, and stress-drop values on the San Andreas fault range from 0.18 to 63 MPa. The observation of constant duration on the San Andreas fault is consistent with a model of a locked asperity in a creeping fault. The differences in durations between the events on the San Andreas fault and on secondary faults suggest that earthquakes on the San Andreas fault are inherently different. We speculate that faults w...
Journal of Geophysical Research, 1993
Three-dimensional finite element calculations are employed to study interactions in space and time between the creeping segment of the San Andreas fault in central California and the adjacent currently locked zones of the 1857 and 1906 great earthquakes. Vertically, the model consists of an elastic upper crust over a Maxwell viscoelastic region, representing the entire lower crust or a narrower horizontal detachment layer, and a stiffer and more viscous upper mantle. The crust has a single vertical fault extending to the top of the mantle at 25 km depth. In zones along strike corresponding to the 1857 and 1906 events, the top 12.5 km of the fault is locked against slip, except in great earthquakes. Below the locked zones and everywhere along the creeping region between them, the fault is freely slipping. The model parameters are compatible with seismological and geological observations, and with a ratio of Maxwell relaxation time to the relaxing layer thickness in the range 1 to 2 yr/km, as established by Li and Rice (1987) and Fares and Rice (1988) based on fits to geodetic data along the San Andreas fault. An imposed constant far field shear motion and periodic 1857-and 1906 -type earthquakes generate slip rates along the creeping fault segment that evolve in time throughout the entire earthquake cycle. Shortly after an adjacent great earthquake, slip rates in the creeping zone are higher than the far field velocity, while later in the cycle they are lower. Hence, time dependency should be accounted for when measurements of fault slip are used to estimate the plate motion. If Parkfield earthquakes are a response to a time dependent loading of the type simulated here, their recurrence interval would tend to lengthen with time since the 1857 event. Thus, the hypothesis of characteristic periodic earthquakes at Parkfield may not provide the best estimate of the occurrence time of the next event. Using, for example, the statistics of past events and assuming that Parkfield earthquakes are a response to a slip deficit near Middle Mountain, and that the elastic crustal layer is 17.5 km thick, we find that the next event is predicted for about 1992 __ 9 years if the lower crust is a 7.5 km thick layer having a material relaxation time of 15 years, and 1995 ñ 11 years if the 7.5 km thick lower crust is characterized by a relaxation time of 7.5 years. These values may be compared to the 1988 ñ 7 years estimate based on periodicity in time. The modeling results also indicate that the interaction between the 1857 and 1906 rupture zones is small. 1906 ;URFACE EAK BQutl•tg Hollister K• Kine oClty 50 J Porkfield GH
Stress Triggering of the 1994 M = 6.7 Northridge, California, Earthquake by Its Predecessors
Science, 1994
A model of stress transfer implies that earthquakes in 1933 and 1952 increased the Coulomb stress toward failure at the site of the 1971 San Fernando earthquake. The 1971 earthquake in turn raised stress and produced aftershocks at the site of the 1987 Whittier Narrows and 1994 Northridge ruptures. The Northridge main shock raised stress in areas where its aftershocks and surface faulting occurred. Together, the earthquakes with moment magnitude M >/= 6 near Los Angeles since 1933 have stressed parts of the Oak Ridge, Sierra Madre, Santa Monica Mountains, Elysian Park, and Newport-lnglewood faults by more than 1 bar. Although too small to cause earthquakes, these stress changes can trigger events if the crust is already near failure or advance future earthquake occurrence if it is not.