Earthquake swarms in circum-Pacific subduction zones

Holtkamp, S. G.; Brudzinski, M. R.

doi:10.1016/j.epsl.2011.03.004

Cited by 72 publications

(66 citation statements)

References 34 publications

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“…Most studies associated with earthquake swarms appear to point to the migration of hydrothermal fluids (Heinike et al, 2009) or magma injection (Špičák, et al, 2000(Špičák, et al, , Kurz et al, 2004 as the cause of tectonically driven swarms; however, the occurrence of swarms has also been attributed to aseismic slip in both subduction zone (Holtkamp and Brudzinski, 2011) with Cenozoic normal faulting. Other areas with intraplate swarms that do not appear to be associated with fluid migration include Arkansas (Špičák, 2000;Rabak et al, 2010) and Canada (Ma and Eaton, 2009).…”

Section: Chapter 4 Summary and Future Directionsmentioning

confidence: 99%

Seismicity within Arizona during the Deployment of the EarthScope USArray Transportable Array

Lockridge¹,

Fouch²,

Arrowsmith³

2012

Bulletin of the Seismological Society of America

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i ABSTRACT The goal of this study is to gain a better understanding of earthquake distribution and regional tectonic structure across Arizona. To achieve this objective, I utilized seismic data from EarthScope's USArray Transportable Array (TA), which was deployed in Arizona from April 2006 to March 2009. With station spacing of approximately 70 km and ~3 years of continuous three-component broadband seismic data, the TA provided an unprecedented opportunity to develop the first seismicity catalog for Arizona without spatial sampling bias. In this study I developed a new data analysis workflow to detect smaller scale seismicity across a regional study area, which serves as a template for future regional analyses of TA data and similar datasets.The final event catalog produced for this study increased the total number of earthquakes documented in Arizona by more than 50% compared to the historical catalog, despite being generated from less than three years of continuous waveform data. I combined this new TA catalog with existing earthquake catalogs to construct a comprehensive historical earthquake catalog for Arizona. These results enabled the identification of several previously unidentified areas of seismic activity within the state, as well as two regions characterized by seismicity in the deeper (>20 km) crust. The catalog also includes 16 event clusters, 10 of which exhibited clear temporal clustering and swarm-like behavior. These swarms were distributed throughout all three physiographic provinces, suggesting that earthquake swarms occur regardless of tectonic or physiographic setting. I also conducted a case study for an earthquake swarm in June of 2007 near Theodore Roosevelt Lake, approximately 80 miles northeast of Phoenix. Families of events showed very ii similar character, suggesting a nearly identical source location and focal mechanism. We obtained focal mechanisms for the largest of these events, and found that they are consistent with normal faulting, expected in this area of the Arizona Transition Zone. Further, I observed no notable correlation between reservoir water level and seismicity. The occurrence of multiple historical earthquakes in the areas surrounding the reservoir indicates that this swarm was likely the result of tectonic strain release, and not reservoir induced seismicity.iii ACKNOWLEDGMENTS

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Section: Chapter 4 Summary and Future Directionsmentioning

confidence: 99%

Seismicity within Arizona during the Deployment of the EarthScope USArray Transportable Array

Lockridge¹,

Fouch²,

Arrowsmith³

2012

Bulletin of the Seismological Society of America

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“…Earthquake swarms along South American and Japanese megathrusts appear to correlate with locations of subducted topography (Holtkamp and Brudzinski, 2011). Tréhu et al (2012) found evidence for small-magnitude earthquake clusters in areas of subducted seamounts along the Cascadia subduction zone.…”

Section: Role Of Rough Downgoing Plate Topographymentioning

confidence: 99%

Subduction zone megathrust earthquakes

2018

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Subduction zone megathrust faults host Earth's largest earthquakes, along with multitudes of smaller events that contribute to plate convergence. An understanding of the faulting behavior of megathrusts is central to seismic and tsunami hazard assessment around subduction zone margins. Cumulative sliding displacement across each megathrust, which extends from the trench to the downdip transition to interplate ductile deformation, is accommodated by a combination of rapid stick-slip earthquakes, episodic slow-slip events, and quasi-static creep. Megathrust faults have heterogeneous frictional properties that contribute to earthquake diversity, which is considered here in terms of regional variations in maximum recorded magnitudes, Gutenberg-Richter b values, earthquake productivity, and cumulative seismic moment depth distributions for the major subduction zones. Great earthquakes on megathrusts occur in irregular cycles of interseismic strain accumulation, foreshock activity, main-shock rupture, postseismic slip, viscoelastic relaxation, and fault healing, with all stages now being captured by geophysical monitoring. Observations of depth-dependent radiation characteristics, large earthquake slip distributions, variations in rupture velocities, radiated energy and stress drop, and relationships to aftershock distributions and afterslip are discussed. Seismic sequences for very large events have some degree of regularity within subduction zone segments, but this can be complicated by supercycles of intermittent huge ruptures that traverse segment boundaries. Factors influencing variability of large megathrust ruptures, such as large-scale plate structure and kinematics, presence of sediments and fluids, lower-plate bathymetric roughness, and upper-plate structure, are discussed. The diversity of megathrust failure processes presents a suite of natural hazards, including earthquake shaking, submarine slumping, and tsunami generation. Improved monitoring of the offshore environment is needed to better quantify and mitigate the threats posed by megathrust earthquakes globally.

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“…in some zones 14 . Furthermore, the characteristics of seismicity differ among tectonic settings 15 .…”

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confidence: 98%

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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Earthquake swarms in circum-Pacific subduction zones

Cited by 72 publications

References 34 publications

Seismicity within Arizona during the Deployment of the EarthScope USArray Transportable Array

Seismicity within Arizona during the Deployment of the EarthScope USArray Transportable Array

Subduction zone megathrust earthquakes

The proportionality between relative plate velocity and seismicity in subduction zones

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