Seasonal seismicity at western United States volcanic centers

Christiansen, L. B.; Hurwitz, Shaul; Saar, Martin O.; Ingebritsen, Steven E.; Hsieh, Paul A.

doi:10.1016/j.epsl.2005.09.012

Cited by 78 publications

(77 citation statements)

References 47 publications

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“…Pore-pressure diffusion is one possible causal mechanism that has received considerable recent attention [cf. Saar and Manga, 2003;Christiansen et al, 2005;Hainzl et al, 2006]. Hydrologic recharge increases pore pressure and thereby decreases effective stress at depth.…”

Section: Discussionmentioning

confidence: 99%

“…[4] We analyze a 21-year seismic catalog (January 1984 to January 2005) from the SAF near Parkfield (http:// quake.geo.berkeley.edu/) ( Figure 1a) using a suite of statistical analyses [Christiansen et al, 2005]. During the past 20 years seismicity has generally increased ( Figure 1b).…”

Section: Methodsmentioning

confidence: 99%

“…[7] To determine the statistical significance of the observed earthquake distribution pattern, we apply a series of five statistical tests following the methodology in Christiansen et al [2005], using a combination of ANOVA tests and a Kruskal-Wallis test [Dixon and Massey, 1983] on both unprocessed and normalized data. Often Fourier series and power spectra are used for these types of analyses; however, the time-series is too short to provide a robust result for annual cycles.…”

Section: Methodsmentioning

confidence: 99%

“…[2] Microearthquakes may be triggered or modulated by climatic forces that have an annual period, implying a causal link between the hydrologic cycle and the mechanical behavior of the upper crust [Gao et al, 2000;Saar and Manga, 2003;Christiansen et al, 2005;Kraft et al, 2006]. This relation implies that stresses induced by the annual hydrologic cycle are sufficient to fracture near-critically stressed rock either through pore-pressure diffusion [Talwani and Acree, 1984;Shapiro et al, 2003;Hainzl et al, 2006] or loading/unloading of the elastic crust [Heki, 2003].…”

Section: Introductionmentioning

confidence: 99%

“…This relation implies that stresses induced by the annual hydrologic cycle are sufficient to fracture near-critically stressed rock either through pore-pressure diffusion [Talwani and Acree, 1984;Shapiro et al, 2003;Hainzl et al, 2006] or loading/unloading of the elastic crust [Heki, 2003]. In this study, we use a suite of statistical tests [Christiansen et al, 2005] to explore whether seismicity on the San Andreas Fault (SAF) in the vicinity of Parkfield, California, is annually modulated.…”

Section: Introductionmentioning

confidence: 99%

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Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA

Christiansen

Hurwitz

Ingebritsen

2007

Geophysical Research Letters

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We analyze seismic data from the San Andreas Fault (SAF) near Parkfield, California, to test for annual modulation in seismicity rates. We use statistical analyses to show that seismicity is modulated with an annual period in the creeping section of the fault and a semiannual period in the locked section of the fault. Although the exact mechanism for seasonal triggering is undetermined, it appears that stresses associated with the hydrologic cycle are sufficient to fracture critically stressed rocks either through pore‐pressure diffusion or crustal loading/unloading. These results shed additional light on the state of stress along the SAF, indicating that hydrologically induced stress perturbations of ∼2 kPa may be sufficient to trigger earthquakes.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA

Christiansen

Hurwitz

Ingebritsen

2007

Geophysical Research Letters

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A continuous record of intereruption velocity change at Mount St. Helens from coda wave interferometry

et al. 2014

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However, it is unclear from the limited geophysical observations when or if the magma chamber replenished following the 1980-1986 eruptions in the years before the 2004-2008 extrusive eruption. We use coda wave interferometry with repeating earthquakes to measure small changes in the velocity structure of Mount St. Helens volcano that might indicate magmatic intrusion. By combining observations of relative velocity changes from many closely located earthquake sources, we solve for a continuous function of velocity changes with time. We find that seasonal effects dominate the relative velocity changes. Seismicity rates and repeating earthquake occurrence also vary seasonally; therefore, velocity changes and seismicity are likely modulated by snow loading, fluid saturation, and/or changes in groundwater level. We estimate hydrologic effects impart stress changes on the order of tens of kilopascals within the upper 4 km, resulting in annual velocity variations of 0.5 to 1%. The largest nonseasonal change is a decrease in velocity at the time of the deep M w = 6.8 Nisqually earthquake. We find no systematic velocity changes during the most likely times of intrusions, consistent with a lack of observable surface deformation. We conclude that if replenishing intrusions occurred, they did not alter seismic velocities where this technique is sensitive due to either their small size or the finite compressibility of the magma chamber. We interpret the observed velocity changes and shallow seasonal seismicity as a response to small stress changes in a shallow, pressurized system.

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A comprehensive interpretative model of slow slip events on Mt. Etna's eastern flank

Mattia

Bruno

Caltabiano

et al. 2015

Geochem. Geophys. Geosyst.

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Starting off from a review of previous literature on kinematic models of the unstable eastern flank of Mt. Etna, we propose a new model. The model is based on our analysis of a large quantity of multidisciplinary data deriving from an extensive and diverse network of INGV monitoring devices deployed along the slopes of the volcano. Our analysis had a twofold objective: first, investigating the origin of the recently observed slow-slip events on the eastern flank of Mt. Etna; and second, defining a general kinematic model for the instability of this area of the volcano. To this end, we investigated the 2008-2013 period using data collected from different geochemical, geodetic, and seismic networks, integrated with the tectonic and geologic features of the volcano and including the volcanic activity during the observation period. The complex correlations between the large quantities of multidisciplinary data have given us the opportunity to infer, as outlined in this work, that the fluids of volcanic origin and their interrelationship with aquifers, tectonic and morphological features play a dominant role in the large scale instability of the eastern flank of Mt. Etna. Furthermore, we suggest that changes in the strain distribution due to volcanic inflation/deflation cycles are closely connected to changes in shallow depth fluid circulation. Finally, we propose a general framework for both the short and long term modeling of the large flank displacements observed.

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Seasonal seismicity at western United States volcanic centers

Cited by 78 publications

References 47 publications

Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA

Annual modulation of seismicity along the San Andreas Fault near Parkfield, CA

A continuous record of intereruption velocity change at Mount St. Helens from coda wave interferometry

A comprehensive interpretative model of slow slip events on Mt. Etna's eastern flank

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