Journal of Global Positioning Systems (2004)
Vol. 3, No. 1-2: 16-24
The Deformation of Bromo Volcano (Indonesia) as Detected by GPS
Surveys Me t hod
Hasanuddin Z. Abidin, H. And reas, M. Gamal
Department of Geodetic Engineering, Institute of Technology Bandung (ITB), Jl. Ganesha 10, Bandung 40132, INDONESIA
e-mail: [e-mail] Tel: [phone]; Fax: [phone]
M. Hendrasto , On y K . Suganda, M. A. Purbawina ta
Directorate of Vulcanology and Geological Hazard Mitigation (DVGHM), Jl. Diponegoro 57, Bandung 40132, INDONESIA
Irwan Meilano, F. Kimata
Research Center for Seismology and Volcanology and Disaster Mitigation (RCSVDM), Nagoya University, Nagoya, JAPAN
Received: 15 Nov 2004 / Accepted: 3 Feb 2005
Abstract. Bromo is an active type-A volcano located
inside Tengger caldera in East Java province of
Indonesia. In her history, Bromo has erupted at least
about 50 times since 1775. The last eruption occurred on
June 2004. Monitoring of Bromo activities has been
continuously done since early 1989 by using
seismograph. EDM and GPS surveys have also been
conducted since the last eruption in Dec. 2000. Up to now
there have been four GPS surveys that have been
conducted, namely on Dec. 2000, June 2002, August
2003, and June 2004, respectively. The obtained GPS and
EDM results show that the deformation of Bromo
volcano is typically in order of a few cm, with the
inflation and deflation processes before and after the
eruption. Estimated location of the pressure source is
found to be beneath the active crater with depth of about
1 km below the caldera floor.
Key words: Bromo, volcano, deformation, GPS, EDM
1 Introduction
Indonesia has 129 active volcanoes and 271 eruption
points as a consequence of interactions and collisions
among several continental plates. The most actives
volcanoes are shown in Figure 1, which one of them is
Bromo volcano (Tengger caldera) in East Java. With the
people of around 200 million and the fact that most
populated island in Indonesia (i.e. Java) has the most
number of active volcanoes then it is obvious that the
Indonesian people are always live under threat of
volcanic eruptions. According to (Katili & Siswowidjojo,
1994), around 10% of Indonesia people live in the area
endangered by the volcanic eruptions, and about 3 million
of them live in the danger zones. This fact alone suggests
that in Indonesia the monitoring of volcano activity
should be performed not only routinely but should also be
done as good as possible.
Many methods have been utilized for observing and
monitoring the volcano activity, and the efforts for
establishing a good and reliable system for monitoring
and predicting the volcano eruption is never ended
(McGuire et al., 1995; Scarpa and Tilling, 1996). In
relation with the deformation of volcano, it is already
known that the explosive eruptions are usually preceded
by the relatively large inflation of its body (Scarpa and
Gasparini, 1996). In the case of the volcano, which has
been quiet for sometimes, the deformation of its body is
one of the reliable indicators of its reawakening activity.
According to Van der Laat (1996), this point
displacement could reach several tens of meter for silicic
volcano with dome formation; while for volcano with
magma chamber still very deep below or its magma
movement is relatively slow, the observed deformation is
relatively small, where its strain value sometimes is
smaller than 0.1 ppm/year. Moreover, according to Van
der Laat (1996) and Dvorak and Dzurisin (1997), the
deformation of volcano body represented by the point
displacement vectors and their velocity vectors could
provide information on the characteristics and dynamics
of magma chamber. In other word, the deformation
information could be modelled to derive the location,

Abidin et al: The Deformation of Bromo Volcano as Detected by GPS Surveys Method 17
depth, shape, and size of the pressure source causing the
deformation, which is usually called the magma (and
hydrothermal) chamber; while the information on the
deformation rate could be used to derive the pressure
variations inside the magma chamber, which then can be
used in predicting the magma supply rate to the volcano
and its outgoing volume in case of eruption (Dvorak and
Dzurisin, 1997).
Fig. 1 Location of major active volcanoes of Indonesia.
Volcano deformation monitoring could be performed by
utilizing several methods, such as EDM (Electronic
Distance Measurement), levelling, tiltmeter
measurements, GPS surveys and InSAR (Interferometric
Synthetic Aperture Radar) (Massonnet and Feigl, 1998).
In this paper, the deformation characteristics of Bromo
volcano as observed by GPS and EDM surveys will be
presented and discussed. The explanation is mainly based
on the results and experiences obtained from four GPS
surveys that have been conducted, namely on December
2000, June 2002, August 2003, and June 2004,
respectively; and four EDM surveys performed on
December 2000, June 2002, August 2003 and June 2004.
2 Bromo Volcano
Bromo is an active type-A volcano located inside
Tengger caldera in East Java province of Indonesian. It is
the youngest of several other volcanic cones located
inside a caldera, e.g. Widodaren, Kursi, Segorowedi, and
Batok as shown in Figure 2. The towering conical peak of
Semeru, Java's highest volcano, appears in the
background. The caldera is 9 km x 10 km in size,
surrounded by vertical cliffs of about 50 to 500 m in high,
composed by volcanic rock layers of ancient Tengger
Volcano (DVGHM, 2004). The caldera floor consists of
widely distributed sand deposit in the northern part,
known as A Sand Sea Caldera. In the eastern and
southern part, the caldera floor covered by grass. Bromo
crater has a size of 600m by 800m, with several explosion
holes inside. Its summit has an altitude of about 2329 m
above sea level and about 133 m above the caldera floor.
BATOK
BROMO
SEMERU
WIDODAREN
KURSI
BATOK
BROMO
SEMERU
WIDODAREN
KURSI
Fig. 2 Bromo and her surrounding,
adapted from (Decade Volcano, 2004).
In her history, Bromo has erupted at least about 50 times
since 1775, as shown in Table 1. The eruptions were
mostly Strombolian in type. On the basis of geologic
data, historic activity of Bromo and morphology of
Tengger Caldera, the potential hazards of Bromo eruption
are ejected (glowing) rock fragments, heavy ashfalls and
toxic gases. So far, lahar hazards have never occurred
during Bromo eruptions.

18 Journal of Global Positioning Systems
Tab. 1 Eruption Years of Bromo Volcano.
1775(?), 1767(?), 1804, 1815, 1820, 1822-23, 1825,
1829, 1830, 1835, 1842, 1843, 1844, 1856, 1857,
1858, 1859, 1860, 1865, 1866, 1867, 1868, 1877,
1885, 1886, 1887, 1888, 1890, 1893, 1896, 1906,
1907, 1908, 1909, 1910, 1915, 1916, 1921, 1922,
1928, 1929, 1930, 1935, 1940, 1948, 1949, 1950,
1956, 1972, 1980, 1983, 1984, 1995, 2000, 2004
The two last eruptions occurred on December 2000 and
June 2004, respectively. In the last eruption, Bromo was
abrubtly erupted on 8 June 2004 at 15.26 local time for
about 20 minutes. According to DVGHM (2004) the
explosion was a phreatic type eruption revealed the ash
column rose to 3000 m above the crater rim. Ash
material and stones spread around the crater away in
radius of about 300 m. On 9 June 2004 the volcanic
activities were decreased and no more explosion was
occurred. However there was still the white grey ash
plume rose to about 10-25 m from the crater rim. On 10
and 11 June 2004 the volcanic activity of Bromo is still
relatively low. On 13 and 14 June 2004 there are small
explosions happened causing ash material to rise up to
about 100 m. On 15 June 2004, volcanic activity of
Bromo generally decreased, and its status hazard is
reduced to lower level.
3 GPS and EDM Surveys in Bromo Volcano
Monitoring of Bromo activities has been continuously
done since early 1989 by using seismograph. The GPS
and EDM surveys have also been conducted since the last
eruption in Dec. 2000. Up to now there have been four
surveys conducted for GPS as shown in Table 2. GPS and
EDM surveys were conducted in the same periods, except
for the first survey and September 2002. The first EDM
survey was conducted during the 2000 eruption period,
i.e. December 2000.
Tab. 2 Timing of GPS and EDM Surveys.
GPS Survey Survey Period Observed
Survey - 1 11 Feb. 2001 POS, BTOK,
BRMO, KRSI
Survey - 2 21-22 June
2002
POS, BTOK,
BRMO, KRSI,
BANT, WDDRN
Survey - 3 21-22 Agustus
2003
POS, BTOK,
BRMO, KRSI,
BANT, WDRN,
KWAH
Configuration of GPS deformation monitoring network
for Bromo volcano is shown in Figure 3. POS is the
reference GPS point located around Bromo observatory at
the rim of caldera. WDRN and BANT points are newly
included in the second GPS survey. KWAH is the point
on the crater’s rim and established in the third GPS
survey. The distances between POS and other GPS points
are less than 10 km.
GPS point
POS
GPS reference point
North
BTOK
BRMO
KRSI
BANT
WDRN
Tengger
caldera
GPS point
2 km
GPS reference point
KWAH
Active
Crater
GPS point
POS
GPS reference point
North
BTOK
BRMO
KRSI
BANT
WDRN
Tengger
caldera
GPS point
2 km
GPS reference point
KWAH
Active
Crater
Fig. 3 GPS monitoring network in Bromo.
GPS surveys were conducted jointly by the Dept. of
Geodetic Engineering ITB, DVGHM and RCSVDM
Nagoya University. GPS surveys were conducted using
GPS dual-frequency geodetic type receivers, with
observation session ranging from 6 to 12 hours. GPS
surveys a few days after the 2004 eruption, e.g. on 11, 12,
15 and 16 June 2004, were conducted only using two
GPS receivers.
POS
POS
BATOK
BATOK
BROMO
BROMO
KURSI
KURSI
POS
POS
BTOK
BRMO
KRSI
POS
POS
BATOK
BATOK
BROMO
BROMO
KURSI
KURSI
POS
POS
BATOK
BATOK
BROMO
BROMO
KURSI
KURSI
POS
POS
BATOK
BATOK
BROMO
BROMO
KURSI
KURSI
POS
POS
BTOK
BRMO
KRSI
Fig. 4 EDM monitoring network in Bromo.
The EDM measurements were made between POS station
and BATOK, BROMO, and KURSI stations, as shown in
Figure 4. The EDM surveys were conducted using Leica
DI 20 for the first survey and Leica DI 3000 for the
second.

Abidin et al: The Deformation of Bromo Volcano as Detected by GPS Surveys Method 19
4 Data Processing and Results
GPS data processing were done using BERNESSE 4.2
scientific software (Beutler et al., 2001). Processing is
radially performed from POS. The coordinate of POS
itself is determined from BAKOSURTANAL, the IGS
point located near Jakarta, capital of Indonesia. Precise
ephemeris was used for the processing. The final results
shows that several mm precision level were achieved for
all components of coordinates, as shown in Figure 5.
These results also indicate that GPS data processing has
properly done. Based on GPS coordinates estimated from
four GPS surveys that have been conducted, several
deformation characteristics of Bromo volcano can be
inferred, as discussed in the following sub-chapters. The
related results obtained from EDM surveys will also be
given along the discussion.
4.1 Horizontal and Vertical Displacements
The displacement vectors (dE,dN,dh) are obtained by
differencing the estimated coordinates of GPS stations
obtained from two consecutive surveys. The displacement
vectors obtained from four GPS surveys and their
displacement magnitudes (δd) are shown in Table 3.
0
1
2
3
4
5
1 2 34 56 7 891011121314151617181920212223242526
Latitude
Longitude
Ellipsoidal height
Standard Deviation (mm)
GPS points (from 4 GPS surveys)
0
1
2
3
4
5
1 2 34 56 7 891011121314151617181920212223242526
Latitude
Longitude
Ellipsoidal height
Standard Deviation (mm)
GPS points (from 4 GPS surveys)
Fig. 5 Standard deviations of the estimated coordinates of GPS stations from 4 surveys.
Tab. 3 Coordinate differences and displacement of GPS stations and their standard deviations.
Coordinate differences (mm) Displacements (mm) GPS
Surveys :
1 to 2 dE σ(dE) dN σ(dN) dh σ(dh) δd σ(δd)
BTOK -0.3 2.8 17.8 1.7 -0.4 4.0 17.8 1.7
BRMO 17.0 2.5 8.6 1.0 47.6 3.7 51.3 3.6
KRSI 4.0 3.4 3.5 2.2 29.5 5.2 30.0 5.2
Coordinate differences (mm) Displacements (mm) GPS
Surveys :
2 to 3 dE σ(dE) dN σ(dN) dh σ(dh) δd σ(δd)
BTOK 20.7 2.6 -8.0 1.6 16.8 3.7 27.8 3.4
BRMO 18.3 2.5 -14.0 1.2 23.1 3.5 32.6 3.1
KRSI -7.3 3.0 -7.8 1.8 -152.6 4.6 153.0 4.6
BANT 6.8 2.9 -2.6 2.0 2.3 4.5 7.6 4.5
WDRN -4.9 1.9 -19.9 1.3 23.8 2.9 31.4 2.4
Coordinate differences (mm) Displacements (mm) GPS
Surveys :
3 to 4 dE σ(dE) dN σ(dN) dh σ(dh) δd σ(δd)
BTOK 12.0 1.9 5.4 1.3 8.1 2.8 15.5 2.1
BRMO -25.0 1.6 8.5 1.1 -2.3 2.3 26.5 1.4
KRSI -2.8 1.9 35.4 1.2 12.9 3.0 37.8 1.5
BANT -8.8 2.3 -15.7 1.7 63.4 3.6 65.9 3.5
WDRN -15.0 1.4 -15.3 1.1 1.0 2.2 21.4 1.2

20 Journal of Global Positioning Systems
In order to statistically check the significance of the
displacements derived by GPS surveys, the congruency
test [Caspary, 1987] was performed on the following
variable
δdij = (dEij
2 + dNij 2 + dhij 2)1/2 . (1)
where δdij is the displacement of a station from epoch i
to j. The null hypothesis of the test is that there is no
displacement between the epochs. Therefore:
null hypothesis Ho : δdij = 0 , (2)
alternative hypothesis Ha : δdij ≠ 0 . (3)
The test statistics for this test is:
T = δdij / σ(δdij) , (4)
which has a Student's t-distribution if Ho is true. The
region where the null hypothesis is rejected is [Wolf and
Gilani, 1997] :
⎢T ⎢ > t df,α/2 , (5)
where df is the degrees of freedom and α is the
significance level used for the test. In our case, for GPS
baselines derived using 6 to 12 hours of GPS data with 30
seconds data interval, then df → ∞. Please note that a t-
distribution with infinite degree of freedom is identical to
a normal distribution. If a confidence level of 99% (i.e.
α=1%) is used, then the critical value t ∞,0.005 ∞ is
equal to 2.576 [Wolf and Gilani, 1997]. The
displacements of GPS points and their standard
deviations, i.e. δd and σ(δd), are shown in Table 3 above.
If the values are adopted for the congruency test, then the
testing results show that significant displacement is found
in all the stations in all three observed periods, except for
station BANT in the second observed period (e.g. June
2002 – August 2003). Based on the testing results, it
could be statistically concluded that with 99% confidence
level there were deformation phenomena of Bromo
volcano as observed by four GPS surveys that have been
conducted. The magnitude of deformation is in general in
the level of a few cm.
The example is shown in Figure 6, which is derived from
the first and second GPS surveys conducted in February
2001 and June 2002. These displacements indicate the
inflation of Bromo volcano during that observed period,
after the eruption of December 2000.
-2000 -10000
-300 0
-2000
-1000
0
-3000
POS
BATOK
BROMO
KURSI
Horiz o ntal di sp l acements from G P S su rveys,
from Feb. 2001 to June 2002
Easting ( m )
Northing(m)
5 mm
19 mm
18 mm
Bromo
crater
-2000 -10000
-300 0
-2000
-1000
0
-2000 -10000
-300 0
-2000
-1000
0
-3000
POS
BATOK
BROMO
KURSI
Horiz o ntal di sp l acements from G P S su rveys,
from Feb. 2001 to June 2002
Easting ( m )
Northing(m)
5 mm
19 mm
18 mm
Bromo
crater
-2000 -10000
-300 0
-2000
-1000
0
-1
0
1
2
3
4
5
BATOKBROMO KURSI
Vertical
Displacements
(in cm)
-1
0
1
2
3
4
5
BATOKBROMO KURSI
-1
0
1
2
3
4
5
BATOKBROMO KURSI
Vertical
Displacements
(in cm)
-1
0
1
2
3
4
5
BATOKBROMO KURSI
GPS Stations
Fig. 6 Displacement vectors of from GPS surveys.
4.2 Horizontal Distance Changes
The horizontal distances changes computed based on the
estimated GPS coordinates of the observed stations are
also useful for studying the volcano deformation. Figure
7 gives an example of horizontal distance changes of
(BRMO-BTOK) baseline from the first to the last GPS
surveys. The baseline is closed to the active crater of
Broom, and therefore should be more sensitive to
deformation process of volcano.
Figure 7 shows that since February 2001, the inflation
process of Bromo was occurring for about a few cm in
three years before erupting again in June 8th, 2004. A
few days after the eruption, a deflation process was
occurring for about a few cm in just a week. The
deflation process after the June 2004 eruption of Bromo
is also indicated by the results of EDM measurement as
shown in Figure 8.
The horizontal distance changes of all GPS baselines
related to the June 8th, 2004 eruption are shown Table 4.
The results indicate that the ground deformation related
to June 8 eruption were relatively small, just in the order

Abidin et al: The Deformation of Bromo Volcano as Detected by GPS Surveys Method 21
of a few cm. It also shows that in the period between
August 2003 and 24 June 2004 there was a sign of
deflation of the active crater as also shown in Figure 7.
The horizontal shortening of BTOK-BRMO and BTOK-
KRSI baselines as much as 3.5 cm and 3.2 cm indicates
it. More data however is required to reveal the more
detail ground deformation pattern of Bromo volcano
before and after June 8 eruption.
907.37
907.38
907.39
907.4
907.41
907.42
Feb.2001June 2002Agt.200311 June 200424 June 2004
8 June 2004
eruption
Inflation
Deflation
Baseline : BRMO -BTOK
Horizontal distance (m)
Dec. 2000
eruption
Inflation
907.37
907.38
907.39
907.4
907.41
907.42
Feb.2001June 2002Agt.200311 June 200424 June 2004
8 June 2004
eruption
Inflation
Deflation
Baseline : BRMO -BTOK
Horizontal distance (m)
Dec. 2000
eruption
Inflation
Fig. 7 Horizontal distance changes of (BRMO-BTOK) baseline.
11 June12 June13 June14 Ju ne15 June16 June
14 mm
EDM Slope Dista nce Change
Baseline : POS -BRMO
Deflation
11 June12 June13 June14 Ju ne15 June16 June
14 mm
EDM Slope Dista nce Change
Baseline : POS -BRMO
Deflation
Fig. 8 Slope distance changes of (POS-BRMO) baseline as measured by EDM after the June 8th 2004 eruption.
Tab. 4 GPS derived horizontal distance changes (the eruption occurred on June 8th at 15:26 pm for about 20 minutes).
Distance changes in cm w.r.t . August 2003
Baseline 11 June 12 June 15 June 16 June 24 June
POS-BTOK 1.8 no data no data no data -1.3
POS-BRMO 0.9 no data 0.0 no data 0.8
POS-KRSI no data -1.6 no data -1.5 -3.2
POS-BANT no data no data no data no data 1.8
POS-WDRN no data 0.1 no data 0.9 2.0
BTOK-BRMO 0.1 no data no data no data -3.5
BTOK-KRSI no data no data no data no data -3.2
KRSI-WDRN no data -1.2 no data -0.3 0.6
4.3 Kinematic Positioning Results
In order to see the temporal variation of coordinate
components two eeks after the eruption period, e.g. on
June 23rd, GPS data were processed in differential
kinematic mode using Bernesse 4.2 [Beutler et al., 2001].
The positioning results in North-South (NS), East-West
(EW), and Up-Down (UD) components are given in
Figures 9, 10 and 11, respectively.
The results given in these Figures show that two weeks
after the eruption, i.e. on June 23rd, no deformation
signals appear in the horizontal components of
coordinates (NS and SW components). In the vertical
component, however, there are variations shown with a
few cm variations. These variations, however, may not be
directly associated with the real vertical deformation of
volcano, since no strong explosions were occurring
during that day. More investigation is needed to

22 Journal of Global Positioning Systems
understand the temporal variations of UD components
shown in Figure 11.
23 June 200423 June 200423 June 2004
Fig. 9 Temporal NS Variation of GPS Stations (23 June 2004).
23 June 200423 June 200423 June 2004
Fig. 10 Temporal EW Variation of GPS Stations (23 June 2004).
23 June 200423 June 200423 June 2004
Fig. 11 Temporal UD Variation of GPS Stations (23 June 2004).
4.4 Pressure Source Characteristics
The other problem which is interesting to be investigated
is related to the determination of pressure source
characteristics, i.e. its depth, size, shape, and supply rate,
from the GPS derived ground displacement vectors of the
points located on the body of volcano and its surrounding
area. Pressure source modelling of volcano deformation
actually can be based on several models [Mogi, 1958;
Okada, 1985; Trasatti, 2003].
It should be noted in this case that Mogi model [Mogi,
1958], as shown in Figure 12, is by far the most used and
the simplest model to fit ground deformations in volcanic
area. The model assumes that the Earth’s crust consists of
elastic half-space, the source of deformation is small and
spherical as a point like-source with radial expansion, and
it exerts hydrostatic pressure on the surrounding rocks.
Whilst none of those assumptions strictly apply, many
volcanoes show deformation patterns close to Mogi
theoretical model [McGuire et al., 1995].
∆d = 3a3Pd
4µ(f2 + d2)3/2
∆h = 3a3Pf
4µ(f2 + d2)3/2
∆h
∆d
surface
Pressure
Source
d
f
a
a = the radius of the source sphere
f = the depth to the centre of sphere
d = the radial distance at the surface
P = the change in hydrostatic pressure
in the spherical pressure source
µ = Lame’s constant.
Horizontal and vertical displacements :
Ref. : Mogi (1958)
Fig. 12 Mogi Model.

Abidin et al: The Deformation of Bromo Volcano as Detected by GPS Surveys Method 23
Based on the results of first and second GPS surveys,
Mogi model was then applied to estimate location of the
pressure source. Only GPS horizontal displacement
vectors were used in this estimation process and
algorithm proposed by Nishi et al. (1999) was applieed.
Estimated location of the pressure source is found to be
beneath the active crater with depth of about 1 km below
the caldera floor. Figure 13 shows estimated location of
the pressure source. Its local coordinates (Easting,
Northing) with POS as the initial point is about (-2 km, -2
km).
Fig. 13 Location of the pressure source of Bromo volcano
(indicated by the star sign).
5 Closing Remarks
Based on the results of GPS surveys that have been
conducted since February 2001 up to June 2004, it can be
inferred that the deformation of Bromo volcano before
and after eruption is relatively small, i.e. typically in
order of a few cm; with the inflation and deflation
processes before and after the eruption. By using Mogi
model the estimated location of the pressure source is
found to be beneath the active crater with depth of about
1 km below the caldera floor.
Based on the results obtained from deformation
monitoring in Bromo and several other volcanoes in
Indonesia, it can be concluded that GPS survey method is
a reliable method for studying and monitoring volcano
deformation. The method is capable of detecting the
deformation signal that has a relatively small magnitude
in the order of a few cm, or even several mm; although
achieving this level of accuracy is not an easy task to do.
In this case the use of dual frequency geodetic type
receivers is compulsory along with good survey planning,
stringent observation strategy, and stringent data
processing strategy using the scientific software.
Considering its relatively high accuracy, all-times
weather-independent operational capability, wide spatial
coverage, and its user friendliness, the use of repeated
GPS surveys for volcano deformation monitoring is
highly recommended.
Besides those technical aspects, in monitoring the
volcano deformation using repeated GPS surveys there
are some non-technical aspects that have to be considered
and treated properly in order to achieve a relatively good
monitoring performance. Based on our experiences
gained from doing the surveys in Bromo and some other
volcanoes, the operational issues such as team movement
strategy, availability of sufficient power supply and local
labours, preparation of logistic and accommodation for
survey personnel, and communication mechanism among
survey teams, are the issues which took the most efforts
and times to handle and accomplish. The unfriendly and
harsh environment of volcano also should be taken into
consideration in selecting the survey team member.
Although GPS surveys could provide accurate and
precise ground displacement vectors, however in order to
have a better and more detail information on volcano
deformation characteristics, GPS survey method should
be integrated with other monitoring techniques such as
EDM, levelling, tiltmeter measurements and InSAR
(Interferometric Synthetic Aperture Radar) (Massonnet
and Feigl, 1998). With many available data and
information, a more reliable deformation and pressure
source modelling can be better performed.
Acknowledgements
This research project is possible through the cooperation
between the Department of Geodetic Engineering ITB,
Directorate of Volcanology and Geological Hazard
Mitigation (DVGHM), and Research Center for
Seismology and Volcanology and Disaster Mitigation
(RCSVDM), Nagoya University Japan. The
administrative, transportation, accommodation and
financials support given by these three institutions are
highly appreciated. We also thank the ITB and RCSVDM
students and the staffs of DVGHM and RCSVDM for
participating in the GPS surveys operation in Bromo
volcano.
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