Temporal change of characteristics of shallow volcano-tectonic earthquakes associated with increase in volcanic activity at Kuchinoerabujima volcano, Japan

Triastuty, Hetty; Iguchi, Masato; Tameguri, Takeshi

doi:10.1016/j.jvolgeores.2009.05.017

Cited by 16 publications

(17 citation statements)

References 12 publications

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“…Time-relationships between variations in temperature and/or composition of hydrothermal fluids and seismic event occurrences have also been observed in other volcanoes such as Merapi, Indonesia (RICHTER et al, 2004), Kuchinoerabujima, Japan (TRIASTUTY et al, 2009), Mammoth Mountain,…”

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confidence: 69%

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)

Cannata

Diliberto

Alparone

et al. 2011

Pure Appl. Geophys.

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Seismic activity, ground deformation, and soil and fumarole temperatures acquired during 2004-2007 at Vulcano (Aeolian Islands) are analysed and the time relations among the different time series are discussed. Changes in temperature of fumarolic gases took place during four ''anomalous'' periods () at the same time as an increasing number of volcano-seismic events. In particular, the temperatures at high temperature vents and at steam heated soil ranged in time from 180 to 440°C and from 20 to 90°C, respectively. The maximum daily number of volcano-seismic events was 57, reached during the second anomalous period. This seismicity, characterised by focal depth generally lower than 1 km below sea level (b.s.l.) and composed of different kinds of events associated to both resonance and shear failure processes, is related to the shallow dynamics of the hydrothermal system. During the analysed period, very few volcano-tectonic earthquakes took place and tilt recordings showed no sharp or important changes. In light of such observations, the increases in both temperature and volcano-seismic events number were associated to increases in the release of gas from a deep and stable magma body, without magma intrusions within the shallow hydrothermal system. Indeed, a greater release of gas from depth leads to increased fluid circulation, that can promote increases in volcano-seismic events number by both fracturing processes and resonance and vibration in cracks and conduits. The different trends observed in the measured geochemical and geophysical series during the anomalous periods can be due to either time changes in the medium permeability or a changing speed of gas release from a deep magma body. Finally, all the observed variations, together with the changing temporal distribution of the different seismic event kinds, suggest that the hydrothermal system at Vulcano can be considered unsteady and dynamic.

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confidence: 69%

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)

Cannata

Diliberto

Alparone

et al. 2011

Pure Appl. Geophys.

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“…Hypocenters of shallow volcano-tectonic (VT) earthquakes in 2006 estimated by Triastuty et al (2009) are distributed at depths of 200-600 m asl beneath Shindake crater and coincide with the size and location of the obtained deformation source. They suggested that shallow VT earthquakes were caused by the intrusion of hydrothermal fluids into cracks beneath the crater and extensional stress resulted by the shallow ground inflation source.…”

Section: Search Rangementioning

confidence: 82%

“…Yamamoto et al (2005) and Triastuty et al (2009) assumed a one-dimensional P-wave velocity structure as shown in Table 2. Assuming a Poisson's ratio as 0.25 and V P /V S velocity ratio as 1.73, modulus of rigidity μ can be written as where ρ is the density of ground.…”

Section: Finite Element Methodsmentioning

confidence: 99%

“…, and VT earthquakes zone (Triastuty et al 2009) Ethics approval and consent to participate Not applicable.…”

Section: Competing Interestsmentioning

confidence: 99%

“…The volcano consists of three cones: No-ike, Shin-dake and Furu-dake; and the Shindake is presently active. Phreatic or phreato-magmatic eruptions occurred at the crater or a fissure east of it in 1841 (historically the oldest), 1931-1934, 1945, 1966, and 1980(Triastuty et al 2009). After 34 years dormancy, a phreatic eruption occurred at the Shin-dake crater on August 3, 2014.…”

Section: Introductionmentioning

confidence: 99%

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Ground deformation source model at Kuchinoerabu-jima volcano during 2006–2014 as revealed by campaign GPS observation

Hotta

Iguchi

2017

Earth Planets Space

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We analyzed campaign Global Positioning System observation data in Kuchinoerabu-jima during 2006Kuchinoerabu-jima during -2014. Most benchmarks located around Shin-dake crater showed crater-centered radial horizontal displacements. Horizontal displacements at western rim of the Shin-dake crater were tended to be larger compared to those at eastern rim. In addition, benchmark KUC14 which locates near the cliff at Furu-dake showed westward horizontal displacement rather than crater-centered radial (southward) one. Meanwhile, small displacements were detected at the benchmarks located at the foot of Kuchinoerabu-jima. We modeled the observed displacements applying a finite element method. We set entire FE domain as 100 × 100 × 50 km 3 . We set top of the domain as a free surface, and sides and bottom to be fixed boundaries. Topography was introduced in the area within Kuchinoerabu-jima using digital elevation model data provided by Kagoshima prefecture and elevation information from Google earth, and elevation of the outside area was assumed to be sea level. We assumed a stratified structure based on a one-dimensional P-wave velocity structure. We applied a vertical spheroid source model and searched optimal values of horizontal location, depth, equatorial and polar radiuses, and internal pressure change of the source using the forward modeling method. A spherical source with a radius of 50 m was obtained beneath the Shin-dake crater at a depth of 400 m above sea level. The internal pressure increase of 361 MPa yields its volume increase of 31,700 m 3 . Taking effects of topography and heterogeneity of ground into account allowed reproduction of overall deformation in Kuchinoerabujima. The location of deformation source coincides with hypocenters of shallow volcano-tectonic (VT) earthquakes and the aquifer estimated from a two-dimensional resistivity model by audio-frequency magnetotellurics method. The obtained deformation source may be corresponding to the pressurized aquifer, and shallow VT earthquakes and demagnetization may be caused by pressure and strain accumulation in the rocks around the aquifer. Applying the obtained spherical source to the tilt change before August 3, 2014 eruption, we found that 520 m 3 of volcanic materials were supplied toward shallower in 1.5 h before the eruption. The depth and volume change of deformation source before May 2015 eruption detected by precise leveling surveys is deeper and two orders of magnitude greater compared to that before August 2014 eruption.

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A heating process of Kuchi-erabu-jima volcano, Japan, as inferred from geomagnetic field variations and electrical structure

Kanda

Utsugi

Tanaka

et al. 2010

Journal of Volcanology and Geothermal Research

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Since August 2000, we have recorded the total intensity of the geomagnetic field at the summit area of Kuchi-erabu-jima volcano, where phreatic eruptions have repeatedly occurred. A time series analysis has shown that the variations in the geomagnetic field since 2001 have a strong relationship to an increase in volcanic activity. These variations indicate thermal demagnetization of the subsurface around the presently active crater. The demagnetization source for the early variations, until summer 2002, was estimated at about 200 m below sea level. For the variations since 2003, the source was modeled on the basis of the expansion of a uniformly magnetized ellipsoid. The modeling result showed that the source is located at 300 m above sea level beneath the crater. We carried out an audio-frequency magnetotelluric survey with the aim of obtaining a relation between the demagnetization source and the shallow structure of the volcano. A two-dimensional inversion applied to the data detected two good conductors, a shallow thin one which is restricted to a region around the summit area, while the other extends over the edifice at depths between 200 and 800 m. These conductors are regarded as clay-rich layers with low permeability, which were assumed to be generated through hydrothermal alteration. The demagnetization source for the early variations was possibly located at the lower part of the deep conductor and the source after 2003 lies between the two conductors, where groundwater is considered to be abundant. Based on these results, as well as on seismological, geodetic, and geochemical information, we propose a heating process of the Kuchierabu-jima volcano. In the initial stage, high-temperature volcanic gases supplied from the deep-seated magma remained temporarily at the level around the lower part of the less permeable deep conductor since the ascent path had not yet been established. Then, when the pathway developed as a result of repeated earthquakes, it became possible for a massive flux of volcanic gases to ascend through the conductor. The high-temperature gases reached the aquifer located above the conductor and the heat was efficiently transported to the surrounding rocks through the groundwater. As a consequence, an abrupt increase of the gas flux and diffusion of the heat through the aquifer occurred and the high-temperature zone expanded. Since the high-temperature zone is located beneath another conductor, which acts as caprock, we assume that the energy of the phreatic explosion is accumulated there.The proper evaluation of volcanic activity is an essential problem related to the forecasting of eruptions 2 and the mitigation of volcanic hazards. It can be relatively simple for volcanoes where magmatic eruptions 3 are expected based on historical experience since anomalous phenomena such as swarms of volcano-tectonic 4 earthquakes or notable inflation of the ground are observed in the process of ascent of magma and are iden-5 tified as precursors of eruptions (e.g. Ishihara, 1990; Voight et al., 19...

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Temporal change of characteristics of shallow volcano-tectonic earthquakes associated with increase in volcanic activity at Kuchinoerabujima volcano, Japan

Cited by 16 publications

References 12 publications

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)

Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy)

Ground deformation source model at Kuchinoerabu-jima volcano during 2006–2014 as revealed by campaign GPS observation

A heating process of Kuchi-erabu-jima volcano, Japan, as inferred from geomagnetic field variations and electrical structure

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