Earthquake swarms to the west of Mt Ruapehu preceding its 1995 eruption

Hurst, Arthur F.; McGinty, Peter

doi:10.1016/s0377-0273(99)00019-0

Cited by 63 publications

(80 citation statements)

References 15 publications

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“…The northeast-southwest compression (σ1) in eastern Taranaki, and the corresponding northwest-southeast extension (σ 3 ), are similar to that observed at Waiouru (Hayes et al 2004) and at National Park (Hurst & McGinty 1999;M. Reyners pers.…”

Section: Eastern Taranakisupporting

confidence: 69%

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Tectonics of the Taranaki region, New Zealand: Earthquake focal mechanisms and stress axes

Sherburn

White

2006

New Zealand Journal of Geology and Geophysics

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We present 39 well-determined focal mechanisms for crustal earthquakes from the Taranaki region in western North Island, New Zealand. Earthquake locations, azimuths, and take-off angles were calculated using a 3D velocity model and only those mechanisms with at least 15 clear first motions were considered. Principal stress axes were determined by inverting focal mechanisms and independently by inverting earthquake first motions. Based on misfit values and differences in seismicity and geology we interpret data east and west of Mt Taranaki separately.

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Section: Eastern Taranakisupporting

confidence: 69%

“…Martin Reyners and John Townend made many very helpful comments on an earlier version of this work. Martin Reyners is thanked for supplying a list of permanent seismographs with polarity reversals and stress axes for the National Park earthquakes of Hurst & McGinty (1999). Diagrams were drawn using GMT (Wessel & Smith 1998 …”

Section: Acknowledgmentsmentioning

confidence: 99%

Tectonics of the Taranaki region, New Zealand: Earthquake focal mechanisms and stress axes

Sherburn

White

2006

New Zealand Journal of Geology and Geophysics

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“…Examination of the earthquakes with time showed that locations within the cluster were sufficiently random with no migration occurring (Figure 1). Small seismogenic zones within the Erua cluster also returned changing over time, confirming that the observed changes at FWVZ were not due to changes in the source location ( Figure S2 [21] Variations in the seismicity rate and b-values of nearby earthquake swarms were observed at Mount Ruapehu accompanying the 1995-1996 eruptions [Hurst and McGinty, 1999;Hayes et al, 2004]. Changes in seismicity at proximal swarms have also been observed at other volcanoes around the world such as Augustine Volcano in Alaska [Jacobs and McNutt, 2010], and Unzen and Kuju volcanoes in Japan [Shimizu et al, 1992;Sudo et al, 1998].…”

Section: Discussionmentioning

confidence: 66%

The Erua earthquake cluster and seismic anisotropy in the Ruapehu region, New Zealand

Keats¹,

Johnson

Savage

2011

Geophys. Res. Lett.

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[1] We use seismicity generated from the Erua earthquake cluster (a consistently active area of seismicity about 20 km to the west of Mount Ruapehu) over the last 12 years to study seismic anisotropy in the Ruapehu region. In particular, we search for changes associated with two minor phreatic eruptions on the 4th of October 2006 and the 25th of September 2007. The seismicity rate, magnitude of completeness, focal mechanisms and b-value of the cluster are also examined to investigate whether the characteristics of the seismicity changed over the duration of the study. The hypocenters were relocated, which revealed a westward dip in the shallow seismicity. Shear wave splitting results revealed a decrease in delay time in the 2006-2007 period and a significant variation in the fast shear wave polarization in the same time period. The b-value also increased significantly from 1.0 ± 0.2 in 2004 to a peak of 1.8 ± 0.2 in 2007, but no other parameters were found to vary significantly over this time period. We attribute these changes to an increase in pore-fluid pressure in the Erua region due to fluid movement and suggest that this fluid movement may be associated with the eruptions in 2006 and 2007.

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“…It cycles between 10 and 60 • C over periods of 4-16 months since 1945 (Hurst et al, 1991;Christenson and Wood, 1993;Hurst and McGinty, 1999;Christenson et al, 2010). Eruptions occurred near the peak of heating with seismicity, or, as described above with a cool lake without seismicity.…”

Section: Crater Lakes As Sensitive Indicators Of S Viscositymentioning

confidence: 91%

Idiosyncrasies of Volcanic Sulfur Viscosity and the Triggering of Unheralded Volcanic Eruptions

Scolamacchia¹,

Cronin

2016

Front. Earth Sci.

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Unheralded "blue-sky" eruptions from dormant volcanoes cause serious fatalities, such as at Mt. Ontake (Japan) on 27 September 2014. Could these events result from magmatic gas being trapped within hydrothermal system aquifers by elemental sulfur (S e ) clogging pores, due to sharp increases in its viscosity when heated above 159 • C? This mechanism was thought to prime unheralded eruptions at Mt. Ruapehu in New Zealand. Impurities in sulfur (As, Te, Se) are known to modify S-viscosity and industry experiments showed that organic compounds, H 2 S, and halogens dramatically influence S e viscosity under typical hydrothermal heating/cooling rates and temperature thresholds. However, the effects of complex sulfur compositions are currently ignored at volcanoes, despite its near ubiquity in long-lived volcano-hydrothermal systems. Changes in S-viscosity, leading to system sealing and sudden failure, can potentially occur at other volcanoes worldwide, including calderas, not only during phreatic eruptions. Models of impure S behavior must be urgently formulated to detect pre-eruptive warning signs before the next "blue-sky" eruption.

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Earthquake swarms to the west of Mt Ruapehu preceding its 1995 eruption

Cited by 63 publications

References 15 publications

Tectonics of the Taranaki region, New Zealand: Earthquake focal mechanisms and stress axes

Tectonics of the Taranaki region, New Zealand: Earthquake focal mechanisms and stress axes

The Erua earthquake cluster and seismic anisotropy in the Ruapehu region, New Zealand

Idiosyncrasies of Volcanic Sulfur Viscosity and the Triggering of Unheralded Volcanic Eruptions

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