Statistic analysis of swarm activities around the Boso Peninsula, Japan: Slow slip events beneath Tokyo Bay?

Okutani, Tsubasa; Ide, Satoshi

doi:10.5047/eps.2011.02.010

Cited by 24 publications

(32 citation statements)

References 20 publications

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“…A majority of seismicity accompanying SSEs is observed to have swarm-type behaviour (e.g. Llenos et al 2009;Okutani & Ide 2011;Vallee et al 2013). There is no unique declustered catalogue, because we do not know which events are truly independent.…”

Section: Method: Declustering and Calculations Of Probabilitiesmentioning

confidence: 96%

Quantifying seismicity associated with slow slip events in the Hikurangi margin, New Zealand

Jacobs

Savage

Smith

2016

New Zealand Journal of Geology and Geophysics

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To investigate the relationship between seismicity and slow slip events (SSEs) in the Hikurangi margin we calculate seismicity rates during SSEs using the raw GeoNet earthquake catalogue and a derived sequence catalogue from 2002 through 2011. Most regions have more seismicity during SSEs times; the increase is significant for six out of nine regions. Seismicity regionally accompanying SSEs in the Manawatu and Kapiti regions is part of a cluster of normal faulting earthquakes correlated to a convergence-parallel S Hmax stress direction. Seismicity accompanies the smallest published SSE in 2009, which suggests that the occurrence of seismicity is independent of the total slip. The Manawatu-Kapiti and East Coast regions have, respectively, 1.3 and 1.5 times the average rate of sequences during SSEs. The link between the rate of earthquakes and the timing of SSEs indicates that understanding the connection between the two is important for future hazard analysis and earthquake forecasts. ARTICLE HISTORY

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Section: Method: Declustering and Calculations Of Probabilitiesmentioning

confidence: 96%

Quantifying seismicity associated with slow slip events in the Hikurangi margin, New Zealand

Jacobs

Savage

Smith

2016

New Zealand Journal of Geology and Geophysics

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“…For example, the window from 1 January 1992 to 31 December 2001 includes seismicity from 1 January 1990 to 31 December 1991. For events in a given region and time window, five ETAS parameters were determined (µ,α,c,K and p) using a nonlinear inversion code 9,19 . As the result of nonlinear inversion generally depends on the set of initial values, the initial values were changed at least 100 times to obtain the maximum likelihood solution.…”

Section: Methodsmentioning

confidence: 99%

“…As the result of nonlinear inversion generally depends on the set of initial values, the initial values were changed at least 100 times to obtain the maximum likelihood solution. The error bound for each ETAS parameter was estimated with the two-sigma rule using a Hessian matrix 19 . Although all five parameters were determined, here I focus on µ.…”

Section: Methodsmentioning

confidence: 99%

“…A useful tool that can be applied towards resolving this problem is the epidemic type aftershock sequence (ETAS) model 9,10 , which has been widely used to evaluate the characteristics of seismicity [15][16][17][18][19] . In this model, the earthquake sequence is represented as a point process and probabilities are given for the likelihood of each earthquake being triggered by one of the preceding earthquakes or by a background process other than the observed earthquakes.…”

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confidence: 99%

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The proportionality between relative plate velocity and seismicity in subduction zones

Ide

2013

Nature Geosci

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Maximum earthquake magnitude and the rate of seismic activity apparently differ among subduction zones. This variation is attributed to factors such as subduction zone temperature and stress, and the type of material being subducted 1-5 . The relative velocity between the downgoing and overriding plates controls their tectonic deformation. It is also thought to correlate with seismicity 1,2,6-8 . Here I use the epidemic type aftershock sequence model 9,10 to calculate the background seismicity rate-the frequency of seismic events above magnitude 4.5-for 117 sections of subduction zones worldwide, during the past century. I demonstrate a proportionality relationship whereby relative plate velocity correlates positively with seismicity rate. This relationship is prominent in the southwestern Pacific Ocean. However, although seismically active, this region has not experienced a magnitude 9 earthquake since 1900. In contrast, the Cascadia, Nankai, southern Chilean and Alaskan subduction zones exhibit low background seismicity rates, yet have experienced magnitude 9 earthquakes in the past century. Slow slip occurs in many of these regions, implying that slow deformation may aid nucleation of very large earthquakes. The proportionality relationship could be used to assess the seismic risk between two endmembers: active subduction zones that generate moderate earthquakes and quiet subduction zones that generate extremely large earthquakes.It has long been discussed whether the characteristics of seismicity are spatially variable throughout the world's subduction zones. Pioneering studies 1,2 indicated that the largest earthquake possible for each subduction zone is determined mainly by the subduction velocity and the age of the subducting plate, exemplified by two endmembers: the fast and young Chilean subduction zone, and the old and slow Mariana subduction zone. Thirty years later, this simple concept requires revision 11-13 . For example, an alternative explanation for maximum earthquake size, based on orientation of the stress field and the size of the accretionary prism, has been proposed 4 .Although information on maximum earthquake size is directly useful in seismic risk assessment, it is difficult to estimate because the period over which instrumental observations have been made is shorter than the long recurrence time of very large earthquakes. The length of observation cannot be extended quickly and information on maximum earthquake size has not advanced significantly in the past 30 years, although improvements in seismic observation systems and data processing schemes have enabled detailed discussions on the statistical characteristics of moderate and large earthquakes. For example, the b-value of the Gutenberg-Richter relation shows a statistically significant difference among some subduction zones 13 and swarm-like activity may be spatially limited

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“…Such events occurred in October 2002, August 2007, and October 2011 [e.g., Ozawa et al ., ]. Earlier studies showed that during the swarm periods of 2002 and 2007, the background seismicity rates were elevated by approximately 1 or 2 orders of magnitude [ Llenos et al ., ; Okutani and Ide , ].…”

Section: Applications To Induced Inland Seismicitymentioning

confidence: 99%

Quantitative description of induced seismic activity before and after the 2011 Tohoku‐Oki earthquake by nonstationary ETAS models

Kumazawa

Ogata

2013

JGR Solid Earth

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[1] The epidemic-type aftershock sequence (ETAS) model is extended for application to nonstationary seismic activity, including transient swarm activity or seismicity anomalies, in a seismogenic region. The time-dependent rates of both background seismicity and aftershock productivity in the ETAS model are optimally estimated from hypocenter data. These rates can provide quantitative evidence for abrupt or gradual changes in shear stress and/or fault strength due to aseismic transient causes such as triggering by remote earthquakes, slow slips, or fluid intrusions within the region. This extended model is applied to data sets from several seismic events including swarms that were induced by the M9.0 Tohoku-Oki earthquake of 2011.Citation: Kumazawa, T., and Y. Ogata (2013), Quantitative description of induced seismic activity before and after the 2011 Tohoku-Oki earthquake by nonstationary ETAS models,

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Statistic analysis of swarm activities around the Boso Peninsula, Japan: Slow slip events beneath Tokyo Bay?

Cited by 24 publications

References 20 publications

Quantifying seismicity associated with slow slip events in the Hikurangi margin, New Zealand

Quantifying seismicity associated with slow slip events in the Hikurangi margin, New Zealand

The proportionality between relative plate velocity and seismicity in subduction zones

Quantitative description of induced seismic activity before and after the 2011 Tohoku‐Oki earthquake by nonstationary ETAS models

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