SVC12-01

Room:304

Time:May 26 14:15-14:30

A new method to monitor water vapor cycles in active volcanoes
GIRONA, Tarsilo1 ; COSTA, Fidel1∗ ; TAISNE, Benoit1
1

Earth Observatory of Singapore, Nanyang Technological University

The monitoring of multiple gas species from volcanic plumes in real time is crucial to understand the mechanisms involved inpersistent degassing, and can be used anticipate volcanic unrest and magma ascent towards the surface. Progress in gas remotesensing techniques during the last decades has led to the development of ultraviolet absorption spectrometers and UV cameras,
which enable to monitor SO2 emission cycles in real time, at very high-frequency (about 1Hz), and from several kilometers
away from the volcanic plume. However, monitoring of the more abundant gases, i.e., H2O and CO2, is limited to volcanoes
where infrared spectrometers and infrared lamps can be installed at both sides of the crater rims. In this study, we present a newand simple methodology to register H2O emission cycles from long distances (several kilometers), which is based on the lightscattered by the micrometric water droplets of condensed plumes. The method only requires a commercial digital camera and alaptop for image processing, since, as we demonstrate, there is a linear correlation between the digital brightness of the plumeand its volcanogenic water content. We have validated the method experimentally by generating controlled condensed plumes
with an ultrasonic humidifier, and applied it to the plume of Erebus volcano using a 30 minutes-long movie [1]. The wavelet
transforms of the plume brightness and SO2 time series (measured with DOAS [1]) show two common periodic components inthe bands about 100-250 s and about 500-650 s. However, there is a third periodic component in the band of about 300-450 s in
the SO2 time series that is absent in the brightness time series. We propose that the common periodic components are inducedby magmatic foams collapsing intermittently beneath shallow geometrical barriers composed by bubbles with high content ofboth H2O and SO2, whereas the third periodic component could be induced by foams collapsing beneath a deeper geometricalbarrier composed by bubbles with high content of SO2 but low content of H2O. This is consistent with the fact that most of
the water exsolves at very low pressures. Our new methodology should lead to new insights into magma degassing process andanticipation of volcanic eruptions, in particular when combined with other monitoring methods. [1] Boichu et al. (2010), J.
Volcanol. Geotherm. Res. 195:325.
Keywords: volcano, monitoring, phreatic, camera, Mayon, degassing

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SVC12-02

Room:304

Time:May 26 14:30-14:45

CO2/H2O ratio of volcanic gas: Geochemical index for the evaluation of eruptive potential
OHBA, Takeshi1∗
1

Dep. Chem. School Sci., Tokai Univ.

The dominant volatile species dissolved in magma is H2O and CO2. The degassing of those species generates bubbles inmagma. The bubbles produce the buoyance of magma, driving the magma ascent. Many active volcanoes had been emitting
volcanic gas before the eruptions. The amount of H2O and CO2 in the volcanic gas would be affected by the flux of each species
degassed from magma. Comparing H2O and CO2, the solubility of CO2 in silicate melt is much lower than that of H2O. If weassume an isolated magma with no supply of volatile enriched magma from a deep source, the CO2/H2O ratio of fluid emitted
from the magma will decrease along the progress of degassing. Therefore, the CO2/H2O ratio of volcanic gas could be an index
for the remained amount of volatile in magma. I sampled and analyzed volcanic gases at some active volcanoes in Japan. The
CO2/H2O ratio of magmatic component in volcanic gas was correlated to the eruptive activity of each volcano. As the result,
it is suggested that the volcanoes with the CO2/H2O ratio higher than 0.01 are eruptive. In the following, some examples aredescribed.
Mt Iwate
In 1998, a swarm of volcanic earthquakes happened with the inflation of volcanic body suggesting the intrusion of magma.
However, no eruption occurred finally. The fumaloic gas was sampled during the unrest at the geothermal area near the summit.
The CO2/H2O ratio of magmatic component was 0.008, which was lower than 0.01. The reason why Mt Iwate had not erupted
seems to be the low volatile content by which insufficient of buoyance was generated in magma.
Mt Shinmoe-dake, Kirishima
Before the 2011 eruption, fumaroles with high discharging pressure had been developed within the summit crater. In 1994, thefumarolic gas was sampled and analyzed. The CO2/H2O ratio of magmatic component was 0.03, which was much higher than
0.01. In 1994, a magma enriched in volatile was degassing beneath the volcano, which would be the process of preparation for
the eruption in 2011.
Mt Kusatsu-Shirane
Since the steam explosions in 1982 and 1983, no significant eruptive activity happened at the volcano. In 2000, the fumarolicgas was sampled at the geothermal area north of the summit crater. The CO2/H2O ratio of magmatic component was 0.005,
which was lower than 0.01. On March 2014, a swarm of volcanic earthquake and the inflation of volcanic body took place.
On July 2014, the fumarolic gas was sampled and analyzed again. The CO2/H2O ratio of magmatic component increased to
0.025, which was much higher than 0.01. The low SO2/H2S and H2 concentration were detected, suggesting the temperatureof shallow hydrothermal system beneath the summit crater is normal. The increased CO2/H2O ratio suggests an intrusion ofvolatile enriched magma at the depth.

Keywords: Geochemistry, CO2, H2O, Eruptive potintial, Magma

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SVC12-03

Room:304

Time:May 26 14:45-15:00

Temporal variation of the ash component of the 2014-15 Aso Nakadake eruption
GESHI, Nobuo1∗ ; MIYABUCHI, Yasuo2 ; MIYAGI, Isoji1 ; MIWA, Takahiro3
1

IEVG Geological Survey of Japann, AIST, 2 Kumamoto University, 3 NIEDThe eruption of Aso Nakadake volcano started in the end of November 2014 and keeps continuous emission of volcanic ash.
Most of the volcanic products distributing outside of the crater consist of volcanic ash, though some scoriaceous volcanic bombs
are landed on the crater rim.
We trace the temporal change of the grain components of the volcanic ash. The volcanic ash erupted from the onset of theeruption in November till December 10 contains dark-colored opaque glassy grain and cryptocrystalline black grains. Since
middle of December, pale-brownish glassy grains occupy the major part of the products. These glassy grains are subdivided intoi) blocky grain, with fractured surface, lower vesicle contents, ii) sponge-like grain, with higher vesicle contents surrounded byfractured surface, iii) elongated grain, with smooth surface and elongated bubbles. Some elongated grains show Pele ′ s hairshape. The volcanic ash erupted in December 15-16, 25-27, January 13-16 contains elongated glassy grains.

Keywords: eruption, volcanic ash, magma, Aso

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SVC12-04

Room:304

Time:May 26 15:00-15:15

Radon monitoring at active volcanoes: achievements and perspectives
CORRADO, Cigolini1∗ ; COPPOLA, Diego1 ; LAIOLO, Marco1
1

DST University of Torino, Italy, 2 IGS Kyoto University

Understanding the behavior of fluids in hydrothermal systems is a key factor in volcano monitoring and geothermal exploration.
Moreover, measuring gas emissions in volcanic areas is strategic for detecting and interpreting precursory signals of variations
in volcanic activity, including eruptions and flank instabilities of volcanic edifices.
Among gases, a very peculiar one is radon. Radon is a radioactive gas generated from the decay of uranium bearing rocks,
soils and magmas. The role of radon as a potential precursor of earthquakes has been extensively debated. At this stage ofknowledge, radon anomalies appear to be better suited to forecast eruptive episodes since we know the loci of volcanic eruptions
and we can follow the evolution of volcanic activity. Radon mapping is also an effective tool to assess diffuse and concentrated
degassing at the surface. We hereby present a collection of data on Somma-Vesuvius, Stromboli, Villaricca (Chile) and La
Soufriere (Guadeloupe, Lesser Antilles).
At Somma-Vesuvius, we used a network for radon monitoring to discriminate signals produced by regional earthquakes fromthose derived by the local volcanic seismicity. Moreover, the duration of radon anomalies have been used, together with othergeochemical and geophysical parameters, to infer the permeability of the hydrothermal reservoir and the ascent velocity of fluids.
At Stromboli volcano we were able to detect earthquake-volcano interactions: radon anomalies may be coseismic, precursory,and may also occur with a time-delay in respect to the onset of major regional seismic events. In addition, automatic and real timemeasurements allow us to detect major changes in volcanic activity. The simultaneous collection of environmental parameters
substantially increase the potential role of radon in volcano monitoring since the data are easily collected, transferred, elaborated
and filtered by applying Multiple Linear Regression analysis on the radon signal. We hereby propose a methodological procedurethat can contribute to improve volcano surveillance in the attempt to mitigate volcanic risk.

Keywords: radon, monitoring, diffuse degassing, volcano surveillance, volcanic risk

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SVC12-05

Room:304

Time:May 26 15:15-15:30

Near Field Ionospheric Disturbance by the 2014 Kelud Volcano Observed by GNSS-TEC
NAKASHIMA, Yuki1∗ ; HEKI, Kosuke1 ; TAKEO, Akiko1 ; CAHYADI, Mokhamad nur2 ; ADITIYA, Arif3
1

Department of Earth Sciences, Hokkaido University, 2 Sepuluh Nopember Institute of Technology, 3 Geospatial Information
Agency (BIG)The Kelud volcano, eastern part of the Java Island, Indonesia, erupted on 13 February 2014. This Plinian eruption recorded thestrength 4 in the Volcanic Explosivity Index (VEI). Ionospheric wave from the eruption was detected by the Global Navigation
Satellite Systems - Total Electron Contents (GNSS-TEC) method around the volcano. The ionospheric results were comparedwith seismic records, and the whole excitation scenario has been studied.
The raw GNSS data files in the Receiver Independent Exchange Format (RINEX) were obtained from 37 GNSS stations, andthe TEC information has been extracted from them. These stations were located in the Java, the Sumatra and other small islands
around the volcano, and are operated by Badan Informasi Geospatial (BIG), International GNSS Service (IGS) and Sumatra GPS
Array (SuGAr).
The ionospheric oscillations were detected from slant TEC time series. They continued from 16:25 UT to 19:00 UT, andpropagated as fast as ˜1.0 km/s. The oscillation had frequency peaks at 3.7 mHz, 4.6 mHz, and 6.7 mHz. The former two
components coincide with the two lowest atmospheric eigenfrequencies. The 6.7 mHz may correspond to one of the higher
modes.
GEOFON (15 broadband seismometers; STS-1) also detected seismic waves excited by the eruption. The time series showed
one Rayleigh pulse at 16:15 UT, and following continuous acoustic waves. One of the GEOFON stations, UGM, is locatedabout 200 km away from the volcano. The seismic wave of the eruption was clear and the components with periods 200-300
sec continued from 16:25 to 19:00. It lasted ˜1 hour longer than shorter period components. GSN (78 broadband seismometers;
STS-2) recorded the Rayleigh wave from the erupting volcano. Their spectrogram had several clear peaks at frequencies, 3.7mHz, 4.8 mHz, 6.7 mHz, and so on. Some of the components have been excited by atmospheric free oscillation.
These observations indicate the GNSS-TEC results detected free oscillation of the atmosphere excited by continuous Plinian
eruption. This oscillation continued over an hour.
More realistic eigenfrequencies must be inferred in the future considering the atmospheric structure in the region surrounding
the Kelud volcano. It must be compared with other observations, for example infrasound data or airglow, and be considered themechanism of the excitation in detail.
Keywords: GNSS, GPS, Volcano, Ionosphere, Infrasound, Atmospheric resonance

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SVC12-06

Room:304

Time:May 26 15:30-15:45

Combination Mogi and Yokoyama models for ground deformation in 2011-2013 at Merapi volcano
AISYAH, Nurnaning1∗
1

CVGHM

Merapi is a strato volcano located at the border of central Java Provinces and Yogyakarta Special Region, Indonesia. Aftera big eruption in 2010, eruptions with VEI I occurred on 15 July 2012, 22 July 2013 and 18 November 2013. Characteristicof eruption is one of the indicators of volcano hazard mitigation; therefore this research has a purpose to estimate locations ofpressure source and magma supply volume during the period from 2011 to 2013, based on ground deformation obtained by 3
GPS (Global Positioning System) stations installed in December 2010 and 5 additional stations in June 2013. The baselines
beyond the summit crater show extension. This means that Merapi has already entered into inflation process immediately after
the 2010 eruption. The amounts of extension of the baselines from the summit area to the navigation stations range from 5 mm
to 15 mm and the displacements of GPS point varied in 2 mm to 50 mm.
Locations and volume increase of the pressure source were estimated by using Mogi and Yokoyama models. The depth ofpressure source before eruption on 15 July 2012 is 9.8 km and the increase volume is 45 million m3 . Ground deformation related
to the eruptions on 22 July and 18 November in 2013 is modeled by two pressure sources; a deep source of Mogi type and ashallow one of Yokoyama type. The pressure sources are located at depths of 10.9 km and 4.5 km for the eruption in July andare 8.1 km and 2.9 km for November eruption. Increase in volume of the pressure sources for these eruptions is 10 million m3 .

Keywords: Ground deformation, GNSS, Merapi volcano, pressure source

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SVC12-07

Room:304

Time:May 26 15:45-16:00

Monitoring system of Kelud volcano, Java, Indonesia before and after the February 13,
2014 eruption
NANDAKA, I gusti made agung1∗
1Center for Volcanology and Geological Hazards Mitigation Indonesia

Kelud volcano is located on the island of Java, Indonesia is a very active volcano. The last eruption occurred on February 13,
2014. Monitoring network of Kelud before the eruption on Feb 13, 2014, consists of five Seismic stations, two Tiltmeter stations,
one Water Temperature Sensor, and one CCTV. Tiltmeter data show a gradual change since the beginning of 2011. A few days
before the eruption of February 13, 2014 tiltmeter the data showed a sharp rise. Increase in seismic activity observed since theend of November 2013 and then recorded more frequently in mid January up to early February 2014. It made alert level of Kelud
was raised to Level II on 2 February 2014. All monitoring stations recorded intensive increase in volcanic activities after the alertlevel was raised to Level III on 10 February. The appearance of continuous tremors with over scale amplitude on 13 February
2014 at 21:11 WIB (local time) caused alert level was upgraded to Level IV. Eruption started at 22:50 WIB on February 2014,less than 2 hours after upgrading of alert level.
Eruption with VEI of 3-4 destroyed all of instruments, except one seismic station still work which is located 5 kilometers
south of the crater. After the eruption, Center for Volcanology and Geological Hazard Mitigation (CVGHM) has added several
instruments of monitoring. The monitoring network at Kelud is currently equipped with 5 Seismic stations, 2 Tiltmeters, 2 CCTV,
and 3 additional stations which are equipped with seismic and CCTV for monitoring Lahar. In 2015, the network will be addedwith 3 stations of Seismic, Tiltmeter and continuous GPS as part of Project SATREPS. Until February 2015, activity of Keludvolcano is relatively quiet with volcanic earthquakes less than 10 events/month and domination of tectonic earthquakes. Visually,
the actitivty in the crater is weak emission. Alert level of Kelud volcano is Level I.
Keywords: Kelud volcano, Multiparameter monitoring

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SVC12-08

Room:304

Time:May 26 16:15-16:30

Locally-distributed inflational deformation at Midagahara volcano, Japan, detected by
InSAR time series analysis
KOBAYASHI, Tomokazu1∗ ; HANSSEN, Ramon F.2
1

GSI of Japan, 2 Delft University of Technology

Preface: Midagahara volcano is an active volcano located in the Toyama Prefecture. Jigoku-dani area is known as an active
geothermal area with fumarole and boiling water activity. In these past few years, activity on the ground has become more visibewith burning and flow out of sulfur in 2010 and increased temperatures of fumarole. It is known that phreatic eruptions haveoccurred historically, and therefor there is a current concern about phreatic eruptions in the near future. Generally, a phreatic
eruption is thought to occur by a heat supply to a geothermal system under the ground, probably leading to an inflational crustal
deformation due to pressure increase in the crust. Crustal deformation is valuable information to know what proceeds under the
ground, and can be an important indicator to assess the degree of activity. However, no significant deformation has been observedin recently-conducted GPS observations which were done in and around the Murododaira area which is about 500 m away fromthe geothermal area. It suggests that the crustal deformation, if there would be any, occurs in a small area with small magnitude.
Thus, InSAR time series analysis may contribute to grasp the whole picture of the crustal deformation with its high measurement
accuracy and high spatial resolution.
Data analysis: We used ALOS/PALSAR data observing Midagahara volcano. Only 12 SAR images are available due to thelong-term snow cover, acquired from Jul. 2007 to Oct. 2010. We applied a PSI analysis for the observation but made somechanges in the processing methodology. The land of the analyzed area is covered by tree/grass, thus it is thought that PS points
cannot be extracted well enough to obtain the deformation in detail. Thus we applied the phase linking method in which phasesof distributed scatters (DSs) are optimized so that we can handle as a point equivalent to PS point in PSI analysis. To pick up
PS candidates, we use the signal-to?clutter ratio (SCR) method in addition to amplitude dispersion (AD), because the AD does
not have a good performance for small data set, while SCR can pick up PSCs from a single SLC image. For DSs analysis, wefirst picked up statistically homogeneous pixels for multilooking by applying the 2-sample KS-test (Ferretti et al., 2011), andthen conducted the phase linking. We used the spatio-temporal consistency as a quality indicator (Hanssen et al., 2008) to selectfinal measurement points. Resultantly, the PS of 7094 pixels was obtained in full pixel size of 720000, while we could get the
optimized DSs of 82138, leading that the observation density significantly improves.
Results: We detected locally-distributed ground surface displacement in the Jigoku-dani geothermal area, which is close to
the satellite, namely, inflational deformation. The deformation speed is estimated to be at about 4cm/yr at maximum. The
deformation area is spatially consistent with the area that active fumarole and boiling water are seen on the ground. The timeseries data of displacement is almost linear, suggesting that there is no significant non-linear deformation. The deformation is
locally distributed with the extent of only a few hundreds of meters, strongly suggesting that the deformation source is located atrather shallow. Assuming a sill-shaped source, we constructed the opening crack source model by a simulated annealing method.
The estimated optimal depth is 100 m, which supports the above-mentioned idea. To know the more detailed spatial extent, weconstructed a distributed opening model that consists of 100 by 100 m rectangular sill-patches. The result shows that the major
crack opening concentrates on a local area with the extent of about a hundred meter just below the area centered at Kajiya-jigoku
fumarole vent, and the amount of opening is estimated to be about 10 cm/yr at maximum.
Acknowledgment: This study was supported by JSPS KAKENHI Grant Number 25350494.
Keywords: Midagahara volcano, InSAR time series analysis, Crustal deformation

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SVC12-09

Room:304

Time:May 26 16:30-16:45

Short-term gravity signal during major eruptions at the Sakurajima volcano since 2012
OKUBO, Shuhei1∗ ; YAMAMOTO, Keigo2 ; IGUCHI, Masato2 ; TAKETA, Akimichi1 ; TANAKA, Yoshiyuki1 ;IMANISHI, Yuichi1
1

Earthquake Research Institute, The University of Tokyo, 2 Disaster Prevention Research Institute, Kyoto University

We have discussed long-term (timescale >several months) gravity change at Sakurajima volcano, which has been repeating
frequent Vulcanian eruptions (500˜1,000/year) since 2009 (Okubo et al., IAVCEI 2013). In fact, excellent correlations were
found among the records of absolute gravity, ejected weight of volcanic ash, ground tilt, and infrasound air shock amplitude. The
long-term gravity data were interpreted in terms of magma head height to explain the close correlation among the variables.
In this paper, we deal with rather short-term gravity signals based on continuous absolute gravity measurements since April
2012. After eliminating hydrological disturbances to the gravity field, we find several major eruptive events were associated withprecursory short-term gravity decreases occurring over ˜3 hours followed by quick recoveries lasting ˜3 hours. The gravity signals
occur in synchronization with the volcano’s inflation/deflation as revealed by strain and tilt records, which strongly suggests thatthe gravity signals are due to either building-up of pressure within the volcano or mass transport in the conduit. Since similar
precursory gravity changes were reported during the Vulcanian phase of the 2011 eruption of Shinmoe-dake volcano, Kirishima,
Japan (Okubo et al., 2013), short-term precursory gravity changes might be universal to major Vulcanian eruptions.
Keywords: absolute gravity, crustal strain, vulcanian eruption, Sakurajima

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SVC12-10

Room:304

Time:May 26 16:45-17:00

Source process of small volcanic explosions as inferred from tilt records: Shinmoe-dake,
Kuchierabu-jima, and Ontake-san
NISHIMURA, Takeshi1∗
1

Geophysics, Science, Tohoku Univ.

Small phreatic explosions occurred at Shinmoe-dake in May 2011 and Ontake-san in September 2014 and phreatomagmatic
explosion at Kuchierabu-jima in August 2014 were observed by tilt meters installed at a few kilometers from the active crater ofthe volcanoes. Temporal characteristics of the tilt motions during these small explosions are characterized by initial uplifts toward
the active craters followed by exponential decays indicating deflations of the volcano. The temporal changes of the exponential
decays are compared with predictions from an eruption model assuming pseudo ideal gas flow through a narrow conduit froma chamber (Nishimura, 1998). The comparisons indicates that the observed characteristic are well explained by the prediction.
This strongly suggests that the processes of these small explosions process is simply expressed by a pressure relaxation due tothe withdrawal of ideal gas stored beneath a volcano. The relaxation times, which are related to the cross sectional area of the
conduit, chamber volume, initial velocity of the ejecta and specific heat of the ideal gas, are estimated to be about 3 min. for
Shinmoe-dake and Ontake-san and 20 s for Kuchierabu-jima, respectively.
Keywords: phreatic explosion, tilt, volcano deformation, small explosion, phreatomagmatic explosion

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SVC12-11

Room:304

Time:May 26 17:00-17:15

A fullwaveform seismic event location method for volcano monitoring operations
GRIGOLI, Francesco1∗ ; CESCA, Simone2 ; KRIEGER, Lars3 ; RIVALTA, Eleonora2 ; AOKI, Yosuke4
1

Institute of Earth and Environmental Sciences, University of Potsdam, Germany, 2 GFZ German Research Centre for Geoscience, Section 2.1 Earthquake and Volcano physics, Germany, 3 School of Earth and Environmental Sciences, University of
Adelaide, Australia, 4 ERI, Earthquake Research Institute, University of Tokyo, Japan
Automated seismic event location procedures are very important tasks in almost all seismological applications, including
seismic monitoring of volcano activity. The large datasets produced during these operations pushed the development of new automated location methods. Seismic waveforms recorded in volcanic environments are often characterized by low signal-to-noise
ratio, thus a successful data analysis requires noise robust automated location procedures. Standard automated location methods
based on automated picking of the main seismic phases (generally only P and S first onsets) are prone to fail with noisy data,
limiting the location performance. In this work we apply the waveform stacking location method developed by Grigoli et al.
(2013, 2014) to volcanic environments. This is a noise robust and picking free location method that exploits the full waveform
information content of seismic recordings. Starting from raw seismograms, the first step of the location process consists in thecomputation of a P-phase and a S-phase stacking functions. For the P phase we use the STA/LTA of the vertical energy trace,
whereas for the S we use the STA/LTA of a trace obtained using the principal eigenvalue of the instantaneous covariance matrix(Vidale 1991). For a given source location, we sum both P and S stacking functions along the theoretical travel times corresponding to the selected hypocenter. To locate a seismic event we iterate this procedure for all samples of the recorded traces
and for all possible source locations within a predetermined seismogenic volume. In this way we retrieve a multidimensional
coherence matrix whose absolute maximum corresponds to the spatio-temporal coordinates of the seismic event. Here we present
an application to a sample dataset for the 2011 unrest at Kirishima volcano, Japan. We show that this automated location method
is particularly suitable for volcano monitoring applications, where large datasets are produced and need to be processed fastly.
Keywords: Seismic event location, Volcano seismology, Microseismic monitoring

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SVC12-12

Room:304

Time:May 26 17:15-17:30

2D AND 3D SEISMIC ATTENUATION TOMOGRAPHIES IN ACTIVE VOLCANOESPRUDENCIO, Janire1∗ ; TAKEO, Minoru1 ; AOKI, Yosuke1 ; IBANEZ, Jesus2
1

Earthquake Research Institute, University of Tokyo, 2 Andalusian Institute of Geophysics, University of Granada

One of the last major challenges in volcano-seismology has been to obtain the internal structure of volcanoes by using seismic
tomographic inversions and discern the role played by the fluids involved in volcanic eruptions. Despite this progress, a few
indeterminations are present in the geological interpretation based on the tomography images, due to the resolutions limits ofthe tomography techniques and the difficulty in associating the physical parameters deduced by the tomography with the rockproperties. The most common way to solve this lack of coverage is to perform active seismic experiments. However, working
with active data, P-wave tomography images are straightforward, while S-wave images, on the contrary, are almost impossible
due to the lack of direct S-wave generation by shots. Moreover, the unclear association of the tomography-deduced parameterswith the rock properties is a well know uncertainty of the current seismological research, which despite from lab work carriedout till now, needs more advances.
A way to partly overcome these difficulties is to jointly interpret tomography images based on the measurement of different
physical quantities. Thus, there are a few (but increasing) cases in which velocity tomography is associated with seismic wave
attenuation imaging. This association is essential in volcanoes, where a correct interpretation of the spatial distribution of thephysical properties in terms of partial melt materials is necessary.
The Coda-Normalization (CN) method is the more novel method for estimating seismic attenuation, which measures the decrease of the seismic energy. The attenuation parameter can be obtained by measuring the direct P- or S-wave energy and thecoda-wave energy, calculating their ratio and inverting the given equation. On the other hand, the presence of magma in volcanic
regions leads to the hypothesis that the predominant cause of seismic energy attenuation is the heat dissipation mechanism (intrinsic attenuation), but observations show that in volcanoes the heterogeneities (scattering attenuation) are the widely predominantcause of energy dissipation. Using the Transport equation in the asymptotic diffusion approximation, we are able to obtain whichis the contribution of each phenomena to seismic energy attenuation and to separately obtain intrinsic and scattering seismic
attenuation 2D images.
Results of the present work will help to better constrain the P-wave velocity images obtained in Deception, Teide, Asama
and Stromboli volcanoes (among others) and will give soon other useful quantitative constraints for a complete geological andvolcanological interpretation which will help to prepare a more accurate volcano-dynamic models.
Keywords: Seismic attenuation, Scattering, Tomography, Volcano-Seismology

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SVC12-13

Room:304

Time:May 26 17:30-17:45

Preliminary ambient seismic noise study in the Tatun Volcano Group of Taiwan
HUANG, Yu-chih1∗ ; LIN, Cheng-horng2 ; KAGIYAMA, Tsuneomi1
1

Aso Volcanological Laboratory, Kyoto University, Kumamoto, Japan, 2 Institute of Earth Sciences, Academia Sinica, Taipei,
TaiwanThe Tatun Volcano Group (TVG) is located in the northern tip of Taiwan and also beside Taipei metropolis. TVG is one of thepotentially active volcano regions on the Taiwan Island and was predominantly active in the Quaternary. Besides, an active fault(named Shanchiao Fault) transits the center of the TVG along the northeastern orientation. Since the major geothermal activities
expose on the surfaces along the hanging wall of the Shanchiao Fault, it is thought to be a passage for gas, fluid, and magma. But
the magma chamber and detailed velocity structures below the TVG are not well resolved.
Studying continuously ambient seismic noise to obtain S-wave velocity structure beneath a densely seismic array is well
performed around the world in the past decade. Seismic activity at TVG has been monitored by a dense seismic array witharound 20 permanent broadband stations operated by Taiwan Volcano Observatory at Tatun (TVO). Since 2014, there are 20 more
temporal broadband stations widely and evenly installed at TVG, supported by Central Geological Survey (CGS) of Taiwan. It
is a good opportunity to study ambient seismic noise to investigate more detailed S-wave velocity structure in the shallow crustand searching for possible candidates of magma chamber beneath TGV. In the meanwhile, we can also relocate seismic eventsand compare seismicity with the newly velocity structure derived from ambient seismic noise. Furthermore, it is a possibility tosearch any velocity variances relate to large seismic events like Shilin earthquake happened on February 12, 2014.
Keywords: ambient seismic noise, Tatun Volcano Group, Taiwan

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SVC12-P01

Room:Convention Hall

Time:May 26 18:15-19:30

Atmospheric effect on infrasound detectablity at Chichi-jima from Nishino-shima assessed by a Monte Carlo phonon method
ICHIHARA, Mie1 ; KIKUCHI, Junji2∗ ; LACANNA, Giorgio3 ; KANNO, Yo1 ; NISHIDA, Kiwamu1
1

ERI, University of Tokyo, 2 Dept. Earth and Planetary Science, University of Tokyo, 3 University of Florence

Nishino-shima volcano in some 1000 km south of Tokyo is active since November, 2013. The new island keeps growing andis almost swallowing the original Nishino-shima island. We installed infrasonic stations to Chichi-jima, which is the closest
inhabited island in 130 km to the east of Nishino-shima, and have been detecting clear infrasonic signals from Nishino-shima
since May 2014. The detection of infrasound at such a distance obviously depends on the atmospheric structure. Here we present
a simple method to evaluate the atmospheric effect, which is crucial for interpreting the infrasonic observation to the change ofvolcanic activity. The method is similar to the Monte Carlo phonon method proposed by Shearer and Earle (2004) to investigate
seismic scattering wave fields.
A million phonon particles were transmitted from the ground to the atmosphere in random directions between zero and 90
degrees in the vertical plane cutting from Nishino-shima to Chichi-jima. Ray-tracing calculation (Tahira, 1982) was performed
for each particles assuming one dimensional atmospheric structure with the effect of wind advection in the plane. We counted
the number of the particles that reached Chichi-jima in the area of the infrasound stations spanning about 1 km, and regarded thatthe number represented the infrasound energy that reached the stations. Perfect reflection was assumed on the sea surface, but
the particles that were trapped in the bottom layer thinner than the scale of the infrasonic wave length were eliminated. The calculation was performed for atmospheric structures from May to December 2014, using the data from radiosonde measurements
twice a day by the Japan Meteorology Agency.
The calculated infrasonic energy arrivals were compared with the power of the signal from Nishino-shima detected by the
infrasonic array at Chichi-jima. The calculation and the observation showed similar tendencies in general confirming that
detection/non-detection of infrasound at Chichi-jima was controlled by atmospheric conditions. However, discrepancies were
found in the beginning of May and in the end of June. The calculation shows infrasound was detectable, but it was not detected by
the observation. These were the periods with low growth rates of the new island according to the satellite image analysis (Maeno
et al., 2014). We conclude that in these periods the non-detection was due to the lack of the infrasonic source at Nishino-shima
and not due to the propagation effect.
Although information for the atmospheric structure is limited, this simple method provides a first-order evaluation for theatmospheric effects and improves the interpretation of the infrasonic data at Chichi-jima for Nishino-shima activity.

Keywords: Volcano, Infrasound, Monitoring, Eruption, Wave propagation

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SVC12-P02

Room:Convention Hall

Time:May 26 18:15-19:30

Characteristics of Eruptions Accompanied with Pyroclastic Flow at Sakurajima Volcano’s
Showa crater
TAMEGURI, Takeshi1∗ ; IGUCHI, Masato1
1

Disaster Prevention Research Institute, Kyoto University

Sakurajima is a post-caldera cone situated on the southern rim of Aira caldera, south Kyushu, Japan. Vulcanian eruptions
have occurred at the Minamidake crater at the summit since 1955. However, principal eruptive activity shifted to the Showa
crater at the eastern flank of the summit in 2006. The eruptions at the Showa crater were phreatic in 2006-2007 and vulcanianeruptions started from 2008. Minor vulcanian eruptions occurred about 1,000 times per year in 2010-2013. Ash plume height ofthe eruptions sometimes reached to 3000-5000m from the crater after 2013. The eruptive activities at the Showa crater become
active and are sometimes accompanied with small pyroclastic flows after 2008. The pyroclastic flow is dangerous volcanic
phenomenon, it is important to understand the mechanism of generation of the pyroclastic flow for disaster prevention. In thisstudy, we research ground deformation and precursory earthquakes patterns before eruptions accompanied with the pyroclastic
flow.
Inflationary strain changes are observed by extensometers a few tens of minutes to several hours prior to the eruptions and arecaused by pressure sources located at depths of 0-1.5 km. The inflation rates decrease or sometimes suspend about 30 minutes
before the eruptions. Small earthquakes dominated by high frequency components (5-6 Hz) swarm when duration of inflation
is longer than 1 hour. The hypocenters of the small earthquakes are located at a depth of 0.5 km beneath the crater and areclose to depth of the pressure source. The earthquakes begin to occur a half hour to 1 hour after the start of the inflation. The
amplitudes and number of the earthquakes further increase when the inflation rates decrease or suspend. Then, the occurrencesof the earthquakes suddenly stop at the start of the eruptions. Inflation duration of the eruptions accompanied with pyroclastic
flow is longer (more than 1.5 hours).
Seismic energy releases of the precursory earthquakes accelerate before the eruptions, although there are all kinds of large
and small seismic energy releases. The precursory earthquake may be generated by release of excess pressure accumulated byinflation of the pressure source. The accelerations of the seismic energy releases before eruptions with the pyroclastic flow tend
to be larger than those with normal events. We could be possible to predict generation of the pyroclastic flow from monitoring of
the inflation duration and the seismic energy release of precursory earthquakes.

Keywords: Sakurajima volcano, pyroclastic flow, explosive eruption

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SVC12-P03

Room:Convention Hall

Time:May 26 18:15-19:30

Recent seismic volcanic activity at Deception Island volcano (Shetland Islands, Antarctica).
SERRANO, Inmaculada1∗ ; CARMONA, Enrique1 ; TORCAL, Federico2 ; DIAZ, Alejandro1 ; JIMENEZ, Vanessa1 ;LORENZO, Francisco1 ; ALMENDROS, Francisco javier1
1

Andalusian Institute of Geophysics, Granada University, Spain, 2 Pablo Olavide University, Seville, Spain

Deception Island is the most active volcano in the South Shetland Islands region, having erupted at least 6 times since it was
first visited 160 years ago. The 15-km-diameter island is horseshoe-shaped and has a flooded caldera (Port Foster) measuring
about 6 x 10 km and a maximum depth of 190 m. All historical eruptions have been relatively small in volume. Evidence forpresent-day volcanic activity at Deception Island includes fumaroles and hydrothermal activity, resurgence of the floor of Port
Foster, and seismicity. Seismic monitoring has been going on since 1986 during austral summer surveys, in which volcanotectonic earthquakes (VT), long-period events (LP) and volcanic tremors, among others, have been recorded with a local networkand seismic arrays.
In this work we analyze the results of the last two Antarctic campaigns conducted by the Spanish research team (2013-2014
and 2014-2015). Although seismic volcanic activity remained at relatively low levels in the 2013-2014 campaign, a notable
increase has been observed in the current campaign (the highest number of LP/VT events in one day is 1500/100). In this paper
we will be discussing the initial results obtained from our analysis of the data, focusing our attention on particular periods ofintense LP and VT activity.
These variations may be related to alterations in the shallow hydrothermal system of Deception Island. In some periods VT
distributions are temporally and spatially homogeneous, with a generally low level of seismicity in certain specific particularareas. These patterns may be caused by different processes, involving regional stresses and local tectonic destabilization inducedby volcanic activity. We investigated how these events may have influenced volcano dynamics. Overall, this study suggests that
there has been a significant reactivation of the volcano since the 2013-2014 Antarctic campaign.

Keywords: seismic array, seismic network, volcano seismology, Shetland Islands, Antarctica

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SVC12-P04

Room:Convention Hall

Time:May 26 18:15-19:30

The sixth round of the repetitive seismic experiment in Sakurajima Volcano, Japan. The
experiment 2014.
TSUTSUI, Tomoki1∗ ; IGUCHI, Masato2 ; NAKAMICHI, Haruhisa2 ; TAMEGURI, Takeshi2 ; IKEDA, Keiji3 ;OSHIMA, Hiromitsu4 ; YAMAMOTO, Mare5 ; NOGAMI, Kenji6 ; OHMINATO, Takao7 ; KOYAMA, Takao7 ;MAEDA, Yuta8 ; OHKURA, Takahiro2 ; SHIMIZU, Hiroshi9 ; YAKIWARA, Hiroshi10 ; KOBAYASHI, Reiji10 ;MAEKAWA, Tokumitsu4 ; HIRAHARA, Satoshi5 ; WATANABE, Atsushi7 ; HORIKAWA, Shinichiro8 ;MATSUHIRO, Kenjiro8 ; YOSHIKAWA, Shin2 ; SONODA, Tadaomi2 ; SEKI, Kenjiro2 ; HIRANO, Shuichiro10 ;HIRAMATSU, Hideyuki3 ; TORIYAMA, Naofumi3 ; KONO, Taisuke3
1

Akita University, 2 Kyoto University, 3 Japan Meteorological Agency, 4 Hokkaido University, 5 Tohoku University, 6 Tokyo Institute of Technology, 7 University of Tokyo, 8 Nagoya University, 9 Kyushu University, 10 Kagoshima University

The sixth round of the repetitive seismic reflection experiment is presented, whose purpose is detection of structurel evolution
associated with underground magma movement in Sakurajima Volcano.
Seismic experiments have been performed every December since 2009 with same field design in the same geometry in thenorthern part of Sakurajima. Two major lines are routinely included in these experiments and comprised with 14 shot points and225 stations every year. Total stations vary depends on state of the year. Uniform instruments, LS-8200SD by Hakusan Industory
and Vertical motion 4.5Hz sensor, and 20kg size chemical explosions are used. 263 stations were deployed in this round, 2014.
In addition to the routine style observation, another type charge, slurry explosive, was tested and accelerations were measured
for all shots. These experiment and observations were performed at the shot point KOME, S07. Four accelerationmeter were deployed ranging 10 to 70m. The nearest station was the force-balancing type triaxial accelerometer, model TSA-100 by Metrozet,
which installed at c.a. 10m from the shot holes. Other three station were the verdumping type triaxial accelerometer, model
JEP-6A3 by Akashi Mitsutoyo, which wereinstalled at 30m and at adjacent of routine stations. Accelerogram were recorded by
the recorders, SC-ADL1000 or SC-ADH10KP, at each station. In order to compare seismograms along the lines, 20kg of slurry
explosives were detoneted at 15m from the dymanaite shot.
The detonation for the sixth round experiment was done on the night 4th December 2014, and that for an additional line wasthe afternoon of 3rd December. 98.5% of all stations were completed schedule and seimograms upto 17Gbytes were obtained
through the experiment. Data suggest that reflectivity under northeast part of Sakurajima have recovered as the same level as anaverage during 2009 to 2011.
On the slurry shot, 80% of peak acceleration was obserbed in near field and its waveform differs less significantly than that bydynamite. Because RMS amplitudes were the same in the routine stations with those from dynamite, it is possible to use slurry
explosives sustainably as alternative of dynamite in our experiment.
This study was supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan, under
its Earthquake and Volcano Hazards Observation and Research Program, also supported by Japan meteorological Agency and
DPRI, Kyoto University. The instruments for routine experiment are provided by Earthquale Research Institute, University ofTokyo. The sensors and recorders were provided by Prof. Tomotaka Iwata, Kyoto University and SCIMOLEX co. The field
operation was supported by Kagoshima Meteorological office, JMA.

Keywords: Sakurajima Volcano, Repetitive seismic experiment, Reflection seismology, Structure evolution, Volcanic structure,
Magma

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SVC12-P05

Room:Convention Hall

Time:May 26 18:15-19:30

Spatial and temporal analysis of stress fields inferred from crack distributions in the Mt.
Fuji volcanic area
ARARAGI, Kohtaro1∗ ; SAVAGE, Martha2 ; BRENGUIER, Florent3 ; OHMINATO, Takao1 ; AOKI, Yosuke1
1

Earthquake Research Institute, University of Tokyo, 2 Victoria University of Wellington, Institute of Geophysics, 3 Institut desSciences de la Terre, University Joseph Fourier
Understanding stress fields is an important topic to interpret geologic processes in volcanoes. After 2011 Tohoku-Oki earthquake, a Mw5.9 event occurred in the area on 15th March 2011. Therefore, this area is assumed to be affected by static anddynamic stress changes recently. We attempted to interpret those stresses from viewpoints of microcrack distribution by measurement of shear wave splitting and seismic interferometry by using seismic data from 24 seismic stations maintained by ERI,JMA and NIED in the Mt. Fuji volcanic region.
We measure shear wave splitting by upper crustal seismic event data from 2009 to 2012. In our measurement, fast polarization
directions near the summit show radial pattern from the summit while those at stations far from the summit direct to the NW-SE.
The pattern of fast polarization directions far from the summit is consistent with the direction of regional stresses.
From previous studies(e.g. Nakamura, 1977; Acocella and Neri, 2009) about dike, fissure eruption patterns and stresses involcanic regions, we assumed that interaction of gravitational effect of the volcanic edifice and the regional stress can results inthe crack distribution near Mt. Fuji. We conducted forward modeling of stress fields around Mt. Fuji to test the hypothesis of theinfluence of stresses on the contrast of the two patterns of splitting. We could reproduce the pattern of fast polarization directions
as directions of maximum horizontal compressions.
Owing to the limitation of the time resolution of shear wave splitting measurement, we could not obtain significant temporalchanges before and after the 2011 Tohoku-Oki earthquake and the Mw5.9 event. In order to interpret possible subtle changesof microcracks during the period, we attempted seismic interferometry in our data. Our preliminary results by vertical channels
show consistent velocity drop with the results of Brenguier et al. (2014). In Brenguier et al. (2014), they used stations 15 km
away from the summit of Mt. Fuji. In this research, we will increase the temporal and spatial resolution of change of seismic
velocity by using 3 components of seismic data within the 15km of the volcanic edifice in addition to Hi-net stations.

Keywords: Mt. Fuji, Shear wave splitting, Seismic interferometry, microcrack, Tohoku-Oki Earthquake, seismic anisotropy

1/1SVC12-P06

Room:Convention Hall

Time:May 26 18:15-19:30

Ground deformation associated with the eruption of Lumpur Sidoarjo mud volcano, east
Java, Indonesia
AOKI, Yosuke1∗ ; SIDIQ, Teguh purmana2
1

Earthquake Research Institute, University of Tokyo, 2 Institute of Technology Bandung

Ground deformation associated with the eruption of Lumpur Sidoarjo mud volcano between 2006 and 2011 has been investigated from Synthetic Aperture Radar images. Marked subsidence has been observed to the west of, as well as around, the vent.
Line-of-sight changes in the both areas decayed since the middle of 2008 with a time constant of 1.5?2.5 years, implying thatthe ongoing eruption won’t last long. This uniform decay time indicates that the western part is connected to the eruption center
since the middle of 2008 to form a system with station- ary geometry. Our observation that the decay started later to the west thanaround the vent suggests that the sub- sidence to the west has been triggered by the mud eruption. A simple modeling suggeststhat 1) the conduit needs to be narrower at depth than at the surface, 2) the effective rigidity of the mud needs to be lower thanthat estimated from the drilled sample, or both to explain the observed decay constant of the deformation.
Keywords: Mud volcano, Ground deformation, Synthetic Aperture Radar, Time-series analysis

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