Uniform California earthquake rupture forecast, version 3 (UCERF3): the time-independent model

Field, Edward H.; Biasi, Glenn P.; Bird, Peter; Dawson, Timothy E.; Felzer, Karen R.; Jackson, David D.; Johnson, K. M.; Jordan, Thomas H.; Madden, Christopher; Michael, Andrew J.; Milner, K. R.; Page, Morgan T.; Parsons, T.; Powers, Peter M.; Shaw, Bruce E.; Thatcher, Wayne; Weldon, Ray J.; Zeng, Yuehua

doi:10.3133/ofr20131165

Cited by 224 publications

(256 citation statements)

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“…This figure is also in broad agreement with numerical earthquake simulations 45 . The notion that segment boundaries larger than 5 km will always arrest slip has since been incorporated into the state-of-the-art UCERF3 rupture forecast models for California 3,4 . Yet a few earthquakes are known to have bridged larger segment boundary distances.…”

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confidence: 99%

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Limitations of rupture forecasting exposed by instantaneously triggered earthquake doublet

et al. 2016

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Earthquake hazard assessments and rupture forecasts are based on the potential length of seismic rupture and whether or not slip is arrested at fault segment boundaries. Such forecasts do not generally consider that one earthquake can trigger a second large event, near-instantaneously, at distances greater than a few kilometers. Here we present a geodetic and seismological analysis of a magnitude 7.1 intra-continental earthquake that occurred in Pakistan in 1997. We find that the earthquake, rather than a single event as hitherto assumed, was in fact an earthquake doublet: initial rupture on a shallow, blind 2 reverse fault was followed just 19 seconds later by a second rupture on a separate reverse fault 50 km away. Slip on the second fault increased the total seismic moment by half, and doubled both the combined event duration and the area of maximum ground shaking. We infer that static Coulomb stresses at the initiation location of the second earthquake were probably reduced as a result of the first. Instead, we suggest that a dynamic triggering mechanism is likely, although the responsible seismic wave phase is unclear. Our results expose a flaw in earthquake rupture forecasts that disregard cascading, multiple-fault ruptures of this type.Continental earthquakes typically rupture diffuse systems of shallow fault segments, delineated by bends, step-overs, gaps, and terminations. The largest events generally involve slip on multiple segments, and whether or not rupture is arrested by these boundaries can determine the difference between a moderate earthquake and a potentially devastating one.Compilations of historical surface ruptures suggest that boundary offsets of ~5 km are sufficient to halt earthquakes, regardless of the total rupture length 1,2 . This value is incorporated into modern, fault-based earthquake rupture forecasts such as the UCERF3 model for California 3,4 , whose goals include anticipating the maximum possible rupture length and magnitude of future earthquakes within known fault systems.However, if earthquakes could rapidly trigger failure of neighbouring faults or fault segments, at distances larger than ~5 km, then such scenario planning could be missing an important class of cascading, multiple-fault rupture. Here we exploit the combination of spatial 3 information captured by satellite deformation measurements and timing information of successive fault ruptures from seismology, to reveal how near-instantaneous, probably dynamic triggering may lead to sequential rupture of multiple large earthquakes separated by distances of 10s of kilometers.The destructive Harnai earthquake occurred on 27 February 1997 at 21:08 UTC (02:08 on 28February, local time) in the western Sulaiman mountains of Pakistan 5 (Figure 1a). Published source catalogues ascribe it a single, largely (85% 99%) double-couple focal mechanism with gentle ~N-dipping and steep ~S-dipping nodal planes and a moment magnitude M w of 7.0 7.1 (Supplementary Table 1 The south-eastern fringe ellipse is caused by slip on another NE-di...

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mentioning

confidence: 99%

“…This value is incorporated into modern, fault-based earthquake rupture forecasts such as the UCERF3 model for California 3,4 , whose goals include anticipating the maximum possible rupture length and magnitude of future earthquakes within known fault systems.…”

mentioning

confidence: 99%

Limitations of rupture forecasting exposed by instantaneously triggered earthquake doublet

et al. 2016

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“…In addition, earthquakes can rupture separate segments; for example, both the 1992 Landers (Sieh et al, 1993) and the 2011 Tohoku-Oki earthquakes (Fry and Ma, 2016) exceeded the maximum magnitude that would have been expected from this approach. The possibility that earthquakes can link different fault segments thus needs to be taken into account (Field et al, 2014).…”

Section: Usual Methodsmentioning

confidence: 99%

“…For example, different studies of the seismicity of California report values of 0.9 (Bakun, 1999), 0.95 (Tormann et al, 2010), 1:02 0:11 (Felzer, 2008), 1:03 0:12 (Page and Felzer, 2015), and 1.05 (Marsan and Lengliné, 2008). A value of about 1 was also determined from both historical and instrumental catalogs (Felzer et al, 2004;Wang et al, 2009;Hutton et al, 2010;Field et al, 2014). These regional b-values are close to the b-values obtained from individual earthquake sequences; for example, the value was 1:09 0:9 for the Landers aftershocks (Felzer et al, 2002).…”

Section: B-valuementioning

confidence: 99%

“…Field et al (1999) predict that an earthquake of magnitude M w > 7:8 will occur every 334 years on average in southern California. According to the Uniform California Earthquake Rupture Forecast, v. 3 (Field et al, 2014), an earthquake of M w 8.25 is feasible every 1000 years. For comparison with these estimates, our model would predict an earthquake above 6.5 roughly once every 10-20 years and an earthquake above 7.8 roughly once every 190-220 years for the entire length of the SAFS.…”

Section: San Andreas Fault Systemmentioning

confidence: 99%

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Determination of Mmax from Background Seismicity and Moment Conservation

Stevens

Avouac

2017

Bulletin of the Seismological Society of America

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We describe a simple method to determine the probability distribution function of the magnitude M max and return period T R of the maximum plausible earthquake on crustal faults. The method requires the background seismicity rate (estimated from instrumental data) and the rate of interseismic moment buildup. The method assumes that the moment released by the seismic slip is in balance with the moment deficit accumulated in between earthquakes. It also assumes that the seismicity obeys the Gutenberg-Richter (GR) law up to M max . We took into account the aftershocks of large infrequent events that were not represented in the instrumental record, so that we could estimate the average seismicity rate over the entire fault history. We extrapolated the instrumental record, using the GR law to model the frequency of larger events and their aftershocks. This increased the frequencies of smaller events on average; when these smaller events were newly extrapolated, they predicted a higher frequency of larger events. We iterated this process until stability was reached, and then we assumed moment balance when we found the maximum magnitude; we have found this method to be appropriate in applications involving examples of fault with good historical catalogs. We then showed examples of applications to faults with no historical catalogs. We present results from nine cases. For the San Andreas fault system, we find

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Fault coupling and potential for earthquakes on the creeping section of the central San Andreas Fault

Maurer

Johnson

2014

JGR Solid Earth

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The 150 km long central section of the San Andreas Fault (CSAF) in central California creeps at the surface and has not produced a large earthquake historically. However, sections of the San Andreas Fault to the north and south are known to have ruptured repeatedly in M~7-8 earthquakes. It is currently unclear whether the creeping CSAF could rupture in large earthquakes, either individually or along with earthquakes on the locked sections to the north and south. We invert Global Positioning System and interferometric synthetic aperture radar data with elastic block models to estimate the degree of locking on the CSAF and place bounds on the moment accumulation rate on the fault. We find that the inferred moment accumulation rate is highly dependent on the long-term fault slip rate, which is poorly constrained along the CSAF. The inferred moment accumulation rate, normalized by shear modulus, ranges from 3.28 × 10 4 to 5.85 × 10 7 m 3 /yr, which is equivalent to a M w = 5.5-7.2 earthquake every 150 years for a long-term slip rate of 26 mm/yr and M w = 7.3-7.65 for a long-term slip rate of 34 mm/yr. The comparisons of slip distributions with microseismicity and repeating earthquakes indicate a possible locked patch between 10 and 20 km depth on the CSAF that could potentially rupture with M w = 6.5.

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Uniform California earthquake rupture forecast, version 3 (UCERF3): the time-independent model

Cited by 224 publications

References 1 publication

Limitations of rupture forecasting exposed by instantaneously triggered earthquake doublet

Limitations of rupture forecasting exposed by instantaneously triggered earthquake doublet

Determination of Mmax from Background Seismicity and Moment Conservation

Fault coupling and potential for earthquakes on the creeping section of the central San Andreas Fault

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