Earthquake supercycles and Long-Term Fault Memory

Salditch, Leah; Stein, Seth; Neely, James S.; Spencer, Bruce D.; Brooks, Edward Μ.; Agnon, Amotz; Liu, Mian

doi:10.1016/j.tecto.2019.228289

Cited by 69 publications

(54 citation statements)

References 72 publications

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“…For example, a logical combination of a southern and northern partial rupture occurred in AD ~15 and ~100, while the AD ~1,465 northern partial rupture was followed by a full‐segment rupture. This shows that long‐term fault memory can be an important factor influencing the occurrence probability and rupture mode of the next earthquake (Salditch et al, 2020) and underscores the need for long paleoseismic records that reconstruct rupture variability in space and time.…”

Section: Discussionmentioning

confidence: 99%

Seismo‐Turbidites in Aysén Fjord (Southern Chile) Reveal a Complex Pattern of Rupture Modes Along the 1960 Megathrust Earthquake Segment

et al. 2020

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Grainsize analysis and end-member modeling of a long sediment core from Aysén Fjord (southern Chile) allows to identify over 25 seismo-turbidites in the last 9,000 years. Considering the shaking intensities required to trigger these turbidites (V½-VI½), the majority can be related to megathrust earthquakes. Multiple studies in south-central Chile have aimed at finding traces of giant, tsunamigenic megathrust earthquakes leading to the current 5,500-year-long paleoseismological record of the Valdivia segment. However, none of these cover the southern third of the segment. Aysén Fjord allows to fill this data gap and presents the first, crucial paleoseismic data to demonstrate that the 1960 event was not unique for the Valdivia segment, yielding a recurrence rate of 321 ± 116 years in the last two millennia. Moreover, the oldest identified events in Aysén Fjord date back to 9,000 cal years BP and, thus, also extend the regional paleoseismological record in time. We infer a large temporal variability in rupture modes, with successions of full-segment ruptures alternating with partial and cascading ruptures. The latter seems to significantly postpone the occurrence of another full rupture when consecutively occurring in different parts of the segment. Additionally, one outstanding period of seismic quiescence-during which no megathrust earthquake evidence has been found at any paleoseismic site-occurred after a full rupture in AD~745 that presents an unusual uplift/subsidence pattern. Such variability makes it highly speculative to anticipate the rupture mode of the next megathrust earthquake along the Valdivia segment.

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Section: Discussionmentioning

confidence: 99%

Seismo‐Turbidites in Aysén Fjord (Southern Chile) Reveal a Complex Pattern of Rupture Modes Along the 1960 Megathrust Earthquake Segment

et al. 2020

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“…Despite these limitations in our SSE catalogue, available data strongly suggest that moment release via SSEs on the shallow portion of the seismogenic plate interface is consistently lower than deep portions (Figures 9, 10, 12, and 13, with depth contours of plate interface shown in gray). Since both the shallow and deep portions of the seismogenic plate interface have locked patches (i.e., areas with high locking rate; Figure 12) that are accumulating elastic strain at high rates during inter‐SSE periods, and the shallow patches release much lower amounts of strain during earthquakes and SSEs, unreleased strain on these shallow portions of the megathrust must accumulate strain in the long‐term (i.e., across multiple seismic cycles) (Salditch et al, 2020). Longer data span and better offshore coverage will help to improve such strain budget estimates and better constrain forecasts of future earthquake magnitude and tsunami potential.…”

Section: Discussionmentioning

confidence: 99%

Slow Slip and Inter‐transient Locking on the Nicoya Megathrust in the Late and Early Stages of an Earthquake Cycle

et al. 2020

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We analyzed continuous GPS data collected from 2002-2020 to characterize slow slip events (SSEs) in and near the Nicoya Peninsula, Costa Rica. These data are bisected by the 5 September 2012 M w 7.6 earthquake. The displacement time series contain multiple signals, including plate convergence, plate interface locking, coseismic and postseismic deformation, seasonal oscillations, SSEs, and noise. GPS-measured coseismic and postseismic displacements associated with the M w 7.6 earthquake are modeled and removed by a step function plus multiple timescale relaxation processes with four characteristic times: 11, 94, 470, and 1,865 days. Seasonal oscillations are eliminated using a multichannel singular spectrum analysis (M-SSA). Ten major SSEs (M w > 6.6) are observed in the remaining time series, with a constant recurrence interval of 21.7 ± 2.6 months. SSEs occur in both shallow (~10 km) and deep (~35 km) portions of the plate interface, but the latter last longer and have larger magnitudes. There is minimum to no slow slip in the M w 7.6 seismic rupture area and a persistent slow slip patch beneath the Nicoya Gulf entrance. Despite strong earthquake-related stress perturbations, the inter-SSE locking status on the megathrust is very similar between the late and early stages of the earthquake cycle and includes locked patches that ruptured in the 2012 earthquake or continue to rupture via SSEs. Some locked patches offshore south of the Nicoya Peninsula did not rupture in 2012, do not participate in SSEs, and may be indicative of supercycle behavior, that is, strain accumulation over several seismic cycles. These areas warrant heightened monitoring. Plain Language Summary Slow slip events (SSEs) release strain energy in Earth's crust that accumulates due to plate motion and frictional locking on the boundaries between plates. SSEs are similar to earthquakes but are less damaging, since strain is released slowly, over weeks or months. We used GPS measurements with millimeter precision to study SSEs in Northwestern Costa Rica between 2002 and 2020 and compared them to the pattern of strain accumulation over the same period. We find that these events happened about every 22 months, and the repeat time is unchanged by the 5 September 2012 M w 7.6 Costa Rica earthquake. Locking patterns also remain similar before and after this earthquake. However, some locked zones did not rupture in the 2012 earthquake or earthquakes in the last few decades and do not participate in SSEs. These areas may represent zones of higher seismic risk in the future.

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“…Values less than zero imply quasiperiodic behavior, B ~ 0 implies a random Poisson process, and values greater than zero imply “bursty” or clustered behavior. Salditch et al (2020) used the nomenclature “strongly periodic” or “weakly aperiodic” for −1 < B < −0.33 (0 < COV < 0.5), “weakly periodic” or “strongly aperiodic” for −0.33 < B < 0 (0.5 < COV < 1), and “bursty” for B > 0 ( COV > 1). We use the terms “strongly periodic” and “weakly periodic” to be clear we are referring to processes more regular than random when B < 0.…”

Section: Methodsmentioning

confidence: 99%

“…Both COV and B ignore the order in which events occur; for example, these measures do not indicate whether shorter interevent times tend to occur consecutively in clusters or separated by longer interevent times (Figures 1a–1c; Chen et al, 2020). For determination of clustering, correlation between consecutive interevent times is important, whereby the conditional probability of a short interevent time following a preceding short interevent time should be greater than the unconditional probability of observing a short interevent time (Livina et al, 2005; Salditch et al, 2020). Goh and Barabási (2008) introduced the term memory coefficient to describe the case of the Pearson sample correlation coefficient calculated between consecutive interevent times:

M = \frac{1}{N - 1} \sum_{i = 1}^{N - 1} \frac{((), τ_{i} - μ_{1}) ((), τ_{i + 1} - μ_{2})}{σ_{1} σ_{2}},

where τ i is the i th interevent time, μ 1 and σ 1 are the mean and standard deviation of the sequence of interevent times τ i ( i = 1, 2, …, N − 1), and μ 2 and σ 2 are the mean and standard deviation of the sequence of interevent times τ i + 1 ( i = 1, 2, …, N − 1).…”

Section: Methodsmentioning

confidence: 99%

“…The term supercycle (Grant & Sieh, 1994;Sieh et al, 2008) has been applied to several types of earthquake behavior but, in general, refers to release of accumulated strain in multiple earthquakes relatively closely spaced in time, followed by long periods of quiescence (Philibosian & Meltzner, 2020). Salditch et al (2020) suggest that supercycles demonstrate long-term memory in the faulting process and that successive large earthquakes are not independent of each other. Clustering has been observed in slowly deforming regions, where periods of quiescence may be orders of magnitude longer than within-cluster interevent times (e.g., Clark et al, 2015;Crone et al, 1997Crone et al, , 2003Taylor-Silva et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

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Periodicity and Clustering in the Long‐Term Earthquake Record

Griffin

Stirling

Wang

2020

Geophysical Research Letters

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Elastic rebound theory forms the basis of the standard earthquake cycle model and predicts large earthquakes to recur regularly through cycles of strain accumulation and release. Yet few individual earthquake records are sufficiently long to test the theory. Here we characterize the distribution of earthquake interevent times from a global compilation of 80 long-term records. We find that large earthquakes recur more regularly than a random Poisson process on individual fault segments. The majority of Earth's well-studied faults shows weakly periodic and uncorrelated large earthquake recurrence, consistent with the expectations of elastic rebound theory. However, many low activity-rate (annual occurrence rates < 2 × 10 −4) faults show random or clustered earthquake recurrence, which cannot be explained by elastic rebound theory. Plain Language Summary To help society prepare for earthquakes, we use the record of previous earthquakes to forecast the chance of future large earthquakes. A key question is whether large earthquakes on a particular fault recur regularly, randomly, or cluster together in time. Here we compile records from 80 different studies of prehistoric earthquakes. We show that large earthquakes on a particular fault recur more regularly than random, except in regions that experience few earthquakes. This means that for regions that experience many earthquakes, we can forecast future large earthquake occurrence with some degree of skill. In contrast, forecasting large earthquake occurrence in places that experience few earthquakes, and where we expect them least, remains exceptionally difficult.

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Earthquake supercycles and Long-Term Fault Memory

Cited by 69 publications

References 72 publications

Seismo‐Turbidites in Aysén Fjord (Southern Chile) Reveal a Complex Pattern of Rupture Modes Along the 1960 Megathrust Earthquake Segment

Seismo‐Turbidites in Aysén Fjord (Southern Chile) Reveal a Complex Pattern of Rupture Modes Along the 1960 Megathrust Earthquake Segment

Slow Slip and Inter‐transient Locking on the Nicoya Megathrust in the Late and Early Stages of an Earthquake Cycle

Periodicity and Clustering in the Long‐Term Earthquake Record

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