Statistical Analyses of Great Earthquake Recurrence along the Cascadia Subduction Zone

Abstract

Goldfinger et al. (2012) interpreted a 10,000 year old sequence of deep sea turbidites at the Cascadia subduction zone (CSZ) as a record of clusters of plate-boundary great earthquakes separated by gaps of many hundreds of years. We performed statistical analyses on this inferred earthquake record to test the temporal clustering model and to calculate time-dependent recurrence intervals and probabilities. We used a Monte Carlo simulation to determine if the turbidite recurrence intervals follow an exponential distribution consistent with a Poisson (memoryless) process. The latter was rejected at a statistical significance level of 0.05. We performed a cluster analysis on 20 randomly simulated catalogs of 18 events (event T2 excluded), using ages with uncertainties from the turbidite dataset. Results indicate that 13 catalogs exhibit statistically significant clustering behavior, yielding a probability of clustering of 13=20 or 0.65. Most (70%) of the 20 catalogs contain two or three closed clusters (a sequence that contains the same or nearly the same number of events) and the current cluster T1-T5 appears consistently in all catalogs. Analysis of the 13 catalogs that manifest clustering indicates that the probability that at least one more event will occur in the current cluster is 0.82. Given that the current cluster may not be closed yet, the probabilities of an M 9 earthquake during the next 50 and 100 years were estimated to be 0.17 and 0.25, respectively. We also analyzed the sensitivity of results to including event T2, whose status as a full-length rupture event is in doubt. The inclusion of T2 did not change the probability of clustering behavior in the CSZ turbidite data, but did significantly reduce the probability that the current cluster would extend to one more event. Based on the statistical analysis, time-independent and time-dependent recurrence intervals were calculated. BSSA Early Edition / 1

Randomness of megathrust earthquakes implied by rapid stress recovery after the Japan earthquake

“…A longer palaeoseismic record along the Cascadia subduction zone showed no evidence for characteristic recurrence either, but suggested a clustered recurrence model 41 . Such behaviour would be equally consistent with the results of our analysis, and could explain how the long-term slip budget is balanced, as the high convergence rate (∼8 cm yr −1 , >1,100 yr interval) suggests a still significant slip deficit along most of the ruptured plate even post-Tohoku-oki.…”

Lake Tutira paleoseismic record confirms random, moderate to major and/or great Hawke’s Bay (New Zealand) earthquakes

“…In the marine realm, which has yielded some of the longest and most complete Holocene paleoseismic records (Kulkarni et al, 2013), major earthquakes are thought to trigger large-volume turbidites in low-gradient, deep-sea basins, because their recurrence intervals also approximate a Poisson distribution (Clare et al, 2014). However, the ubiquitous occurrence of lakes in all active tectonic settings, and the sensitivity and fidelity of lake sediment records over millennial time scales, point to the potential lacustrine earthquake chronologies have for directly validating terrestrial seismic hazard analysis results.…”

“…However, the high-frequency hazard in active tectonic settings originates from a large variety of different seismic sources that generate smaller-magnitude, moderate (M w ≥ 5) earthquakes, which are beyond the resolution afforded by most paleoseismic archives. Thus, there is debate about how best to validate seismic hazard analysis results over millennial time scales (Kulkarni et al, 2013;Baker et al, 2013).…”

“…However, the high-frequency hazard in active tectonic settings originates from a large variety of different seismic sources that generate smaller-magnitude, moderate (M w ≥ 5) earthquakes, which are beyond the resolution afforded by most paleoseismic archives. Thus, there is debate about how best to validate seismic hazard analysis results over millennial time scales (Kulkarni et al, 2013;Baker et al, 2013).Lake sediments can function as natural seismographs and are a receptive but largely unexplored repository of regional-scale information about earthquake ground motions (Strasser et al, 2013, and references therein;Moernaut et al, 2014). We use a new high-resolution paleoseismic archive from Lake Tutira to constrain the recurrence distribution of earthquakes in North Island, New Zealand's Hawke's Bay region with a ground-shaking intensity of Modified Mercalli Intensity (MMI) ≥ 7.…”

Normalized rupture potential for small and large earthquakes along the Pacific Plate off Japan

“…However, this concept and the implied quasiperiodic earthquake recurrence model could not be validated yet [e.g., Kagan et al ., ; Matthews et al ., ]. Moreover, an increasing number of indications from laboratory experiments to natural observations contradict these models and suggest that major earthquakes might not follow a characteristic recurrence in space or time [e.g., Kagan and Jackson , ; Rosenau and Oncken , ; Kulkarni et al ., ; Tormann et al ., ].…”