Tracking volcanic and geothermal activity in the Tongariro Volcanic Centre, New Zealand, with shear wave splitting tomography

Johnson, J. H.; Savage, Martha K.

doi:10.1016/j.jvolgeores.2012.01.017

Cited by 32 publications

(29 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure (top left) contains an inset with the location of the box on a map of New Zealand, the names of all stations and regions, and regions defined in other studies. The boxes with red dashed lines are the Erua and Waiouru regions considered by Godfrey et al [], and the black dashed lines are those considered by Keats et al [] and Johnson and Savage [].…”

Section: Introductionmentioning

confidence: 99%

“…Precursors to eruptions in the region are rare [ Sherburn et al , ], so different approaches have been examined. Seismic velocity changes measured from ambient noise cross correlation [ Mordret et al , ], temporal variation of far‐field seismicity [ Hurst and McGinty , ], temporal variation in seismic attenuation [ Titzschkau et al , ], changes in anisotropy, and b values of nearby swarm areas [ Keats et al , ; Miller and Savage , ; Gerst and Savage , ; Johnson and Savage , ] have all been suggested as being related to changes in stress or fluid content and have all been correlated with activity retrospectively. However, none of those techniques are implemented for standard monitoring yet in New Zealand.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Shear wave automatic picking and splitting measurements at Ruapehu volcano, New Zealand

et al. 2015

Self Cite

View full text Add to dashboard Cite

Automatic shear wave picking and shear wave splitting measurement tools (Multiple Filter Automatic Splitting Technique (MFAST)) are combined to build a near-real time application for monitoring local stress around volcanoes. We use an adapted version of Diehl et al. (2009) on seismograms provided by the New Zealand GeoNet network and having an origin time and location based only on P picks. The best automatic picks are processed by MFAST, which computes the corresponding shear wave fast direction ϕ, and splitting delay time δt, interpreted, respectively, as the principal direction of stress underneath the station and the amount of anisotropy integrated along the wave raypath. We applied our system to 9 years of local earthquakes recorded at seven stations around Ruapehu volcano, New Zealand. Results are compared against MFAST measurements from manual S picks when available and show less than 10°difference for 90% of ϕ measurements and less than 0.05 s difference for 95% of δt measurements. Shear wave splitting from automatic S arrival times are slightly more consistent than those from manual arrival times. At some stations, two populations of delay times occur, which depend upon computed initial polarization. This may be caused in part by cycle skipping, an artifact usually associated with monochromatic signals. However, spatial consistency in the behavior suggests a physical cause as well, such as focal mechanisms varying with earthquake source location or a spatially varying near-source anisotropic region. The numbers of events in each population group vary over time, possibly related to activity at Ruapehu volcano.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shear wave automatic picking and splitting measurements at Ruapehu volcano, New Zealand

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…The mechanism of aligned microcracks is thought to be the only one that allows seismic anisotropy to vary on observable time scales 7 , and temporal changes are traditionally interpreted as stemming from variations in the stress field due to large earthquakes 7 or magmatic intrusions 8 . There is mounting evidence, however, that the dominant mechanism for SWS can switch between a static condition, such as aligned fractures in fault zones, and a dynamic process, such as maximum horizontal compressive stress causing aligned microcracks to dilate 9,10 . In areas where there are strong changes in maximum compressive stress direction and magnitude on observable timescales, such as at active volcanoes, SWS analysis has proven a valuable tool when combined with ground deformation or other seismological observations for interpretation of volcanic processes such as magma migration [8][9][10][11][12][13] .…”

mentioning

confidence: 99%

“…There is mounting evidence, however, that the dominant mechanism for SWS can switch between a static condition, such as aligned fractures in fault zones, and a dynamic process, such as maximum horizontal compressive stress causing aligned microcracks to dilate 9,10 . In areas where there are strong changes in maximum compressive stress direction and magnitude on observable timescales, such as at active volcanoes, SWS analysis has proven a valuable tool when combined with ground deformation or other seismological observations for interpretation of volcanic processes such as magma migration [8][9][10][11][12][13] . Such changes are always detected in hindsight, however, and seismologists struggle to employ monitoring of seismic anisotropy in real-or near-real-time to assist in eruption forecasting.…”

mentioning

confidence: 99%

Seismic detection of increased degassing before Kīlauea's 2008 summit explosion

Johnson

Poland

2013

Nat Commun

Self Cite

View full text Add to dashboard Cite

The 2008 explosion that started a new eruption at the summit of Kı %lauea Volcano, Hawaìi, was not preceded by a dramatic increase in earthquakes nor inflation, but was associated with increases in SO 2 emissions and seismic tremor. Here we perform shear wave splitting analysis on local earthquakes spanning the onset of the eruption. Shear wave splitting measures seismic anisotropy and is traditionally used to infer changes in crustal stress over time. We show that shear wave splitting may also vary due to changes in volcanic degassing. The orientation of fast shear waves at Kı %lauea is usually controlled by structure, but in 2008 showed changes with increased SO 2 emissions preceding the start of the summit eruption. This interpretation for changing anisotropy is supported by corresponding decreases in V p /V s ratio. Our result demonstrates a novel method for detecting changes in gas flux using seismic observations and provides a new tool for monitoring under-instrumented volcanoes.

show abstract

“…In this case, the areas of intense crustal damage are well individuated by large (>0.1s) delay times, and polarisations of the fast S-wave which depart significantly from the NW-SE trend which is expected once accounting for the regional stress field alone. Within this framework, next steps will aim at refining location and depth of the most significant anisotropic rock volumes, by attempting a 3D inversion of the SWS measurements [19].…”

Section: Discussionmentioning

confidence: 99%

The Deep Structure of the Larderello-travale Geothermal Field (Italy) from Integrated, Passive Seismic Investigations

et al. 2014

View full text Add to dashboard Cite

We report the preliminary results from a project (GAPSS-Geothermal Area Passive Seismic Sources), aimed at testing the resolving capabilities of passive exploration methods on a well-known geothermal area, namely the Larderello-Travale Geothermal Field (LTGF). Located in the western part of Tuscany (Italy), LTGF is the most ancient geothermal power field of the world. GAPSS consisted of up to 20 seismic stations deployed over an area of about 50 x 50 Km. During the first 12 months of measurements, we located more than 2000 earthquakes, with a peak rate of up to 40 shocks/day. Preliminary results from analysis of these signals include: (i) analysis of Shear-Wave-Splitting from local earthquake data, from which we determined the areal distribution of the most anisotropic regions; (ii) local-earthquake travel-time tomography for both P-and S-wave velocities; (iii) telesismic receiver function aimed at determining the high-resolution (<0.5km) S-velocity structure over the 0-20km depth range, and seismic anisotropy using the decomposition of the angular harmonics of the RF data-set; (iv) S-wave velocity profiling through inversion of the dispersive characteristics of Rayleigh waves from earthquakes recorded at regional distances. After presenting results from these different analyses, we eventually discuss their potential application to the characterisation and exploration of the investigated area.

show abstract

Tracking volcanic and geothermal activity in the Tongariro Volcanic Centre, New Zealand, with shear wave splitting tomography

Cited by 32 publications

References 33 publications

Shear wave automatic picking and splitting measurements at Ruapehu volcano, New Zealand

Shear wave automatic picking and splitting measurements at Ruapehu volcano, New Zealand

Seismic detection of increased degassing before Kīlauea's 2008 summit explosion

The Deep Structure of the Larderello-travale Geothermal Field (Italy) from Integrated, Passive Seismic Investigations

Contact Info

Product

Resources

About