Background seismicity in Boso Peninsula, Japan: Long‐term acceleration, and relationship with slow slip events

Reverso, T.; Marsan, David; Helmstetter, Agnès; Enescu, Bogdan

doi:10.1002/2016gl068524

Cited by 22 publications

(45 citation statements)

References 42 publications

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“…Similarly, the foreshock sequence in 2008 showed the largest fault slip of repeating earthquakes (1.75 cm; 1.2 times that of the swarm sequence in 2006). Given that background seismicity rates during the time periods of SSEs are known to be broadly proportional to the moment rates of the SSEs (Reverso et al, ), these results imply that the SSEs that triggered the foreshock sequences in 1982 and 2008 had larger seismic moments than the SSEs that produced the swarm sequences. In addition, the large increases in the number of excess events and the amount of fault slip 12 hr before the 2008 Ibaraki‐Oki earthquake imply a large moment rate of the SSE preceding the mainshock.…”

Section: Discussionmentioning

confidence: 84%

Recurring Slow Slip Events and Earthquake Nucleation in the Source Region of the M 7 Ibaraki‐Oki Earthquakes Revealed by Earthquake Swarm and Foreshock Activity

Nishikawa

Ide

2018

JGR Solid Earth

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Slow slip events (SSEs) on the plate interface are closely related to the occurrence of earthquakes and often trigger earthquake swarms in subduction zones. Moreover, some SSEs, accompanied by intensive foreshocks, precede large interplate earthquakes. Therefore, detecting and monitoring SSEs is important for assessing the potential of future large earthquakes. However, there are many SSEs not followed by large earthquakes, and it is unclear whether these can be distinguished from SSEs preceding large earthquakes. Here we use the epidemic‐type aftershock sequence (ETAS) model and matched‐filter technique to examine the spatial‐temporal distribution of earthquake swarms and foreshocks at Ibaraki‐Oki in the Japan Trench. We found that 19 swarm sequences repeatedly occurred during the period 1982–2008 at the same location as the foreshock sequences of the 1982 and 2008 M 7 Ibaraki‐Oki earthquakes. Both the foreshock and swarm sequences contain repeating earthquakes and have anomalously high seismicity rates inexplicable by the ETAS model, suggesting the recurrence of SSEs. The foreshock sequences in 1982 and 2008 contain more events inexplicable by the ETAS model than the swarm sequences. The fault slip of repeating earthquakes in the 2008 foreshock sequence was also larger than those of the swarm sequences, and the slip rate showed an abrupt increase 12 hr before the 2008 M 7 event. Our results imply that the SSEs that preceded the M 7 events had larger seismic moments than the other SSEs. These large SSEs might be related to the nucleation phase of the M 7 earthquakes.

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Section: Discussionmentioning

confidence: 84%

Recurring Slow Slip Events and Earthquake Nucleation in the Source Region of the M 7 Ibaraki‐Oki Earthquakes Revealed by Earthquake Swarm and Foreshock Activity

Nishikawa

Ide

2018

JGR Solid Earth

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“…In both cases, the declustered time series is well modeled by a quadratic fit, i.e., a constant acceleration over 21 or 25 years. Zone G shows extremely marginal overlap with the area (denoted R from there on) analyzed by Reverso et al [], cf. Figure , so this observation is new.…”

Section: Discussionmentioning

confidence: 99%

Change in seismicity along the Japan trench, 1990–2011, and its relationship with seismic coupling

et al. 2017

Self Cite

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We investigate the temporal evolution of the background seismicity rate related to the subduction of the Pacific plate in northeast Japan, at latitudes 34° to 42°, for the 1 January 1990 to 9 March 2011 period. Two declustering methods are used to identify robust features. We find that the dominant behavior is a lowering down of activity, especially in the northern half of our studied area, where changes appear related to the cycle of M7.5+ earthquakes, in particular the 1968 Tokachi and the 1994 Sanriku earthquakes. Acceleration of background seismicity is observed offshore the Kanto region and could mark a long‐term decoupling of the Pacific and the Philippine Sea plates over a 100 km long segment along the Sagimi Trough, which cannot be simply explained by the earthquake cycle model. Our analysis further suggests that changes in background seismicity are plausibly related to changes in seismic coupling and thus further strengthens the recent observation that seismic coupling does vary at the timescales of tens of years, for the Japanese subduction zone.

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“…Another interesting feature revealed by Figures a and b is the fact that the background seismic activity is not continuous in time, but rather occurs by bursts, both for shallow and deep events. These swarms are usually associated with aseismic episodes (Reverso et al, , ). The shallow bursts are associated with swarms detected in 2006, 2008, and 2013 (see supporting information S1 for details), which may indicate the occurrences of SSEs, plus a few isolated background earthquakes between 2005 and 2014 that occur as a response to tectonic loading (Figure ).…”

Section: Discussionmentioning

confidence: 99%

Long‐Term Interactions Between Intermediate Depth and Shallow Seismicity in North Chile Subduction Zone

Jara

Socquet

Marsan

et al. 2017

Geophysical Research Letters

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We document interactions between intermediate depth and interplate seismicity in the North Chile subduction zone, over a 25 year period (1990–2015). We show that the 2005 Mw 7.8 Tarapaca slab‐pull earthquake was followed by 9 years of enhanced deep and shallow seismicity, together with the decrease of eastward average GPS velocities and associated interplate coupling, eventually leading to the 2014 Mw 8.1 Iquique megathrust earthquake. In contrast, megathrust ruptures (e.g., Mw 8.0 Antofagasta in 1995, or Mw 8.1 Iquique in 2014) initiate several years of silent background seismicity in the studied area, both at shallow and intermediate depths. The plunge of a rigid slab into a viscous asthenospheric mantle could explain the observed synchronization between deep and shallow seismicity and their long‐term interactions.

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Background seismicity in Boso Peninsula, Japan: Long‐term acceleration, and relationship with slow slip events

Cited by 22 publications

References 42 publications

Recurring Slow Slip Events and Earthquake Nucleation in the Source Region of the M 7 Ibaraki‐Oki Earthquakes Revealed by Earthquake Swarm and Foreshock Activity

Recurring Slow Slip Events and Earthquake Nucleation in the Source Region of the M 7 Ibaraki‐Oki Earthquakes Revealed by Earthquake Swarm and Foreshock Activity

Change in seismicity along the Japan trench, 1990–2011, and its relationship with seismic coupling

Long‐Term Interactions Between Intermediate Depth and Shallow Seismicity in North Chile Subduction Zone

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