[PDF] After Four Years of Ground Displacements Following LUSI Mud Volcano

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After Four Years of Ground Displacements Following LUSI Mud Volcano

Eruption; Sign of its Ending Eruption

Heri ANDREAS, Hasanuddin Zainal ABIDIN, Mipi Ananta KUSUMA and Irwan GUMILAR, Indonesia

http://77.243.131.160/pub/fig2011/papers/ts02e/ts02e_andreas_abidin_et_al_4901.pdf

Key words: Mud Volcano, Ground Displacement, GPS, exponential decay

ORIGINAL ARTICLE:

SUMMARY

On May 29, 2006 a mud volcano started to form at Porong Sidoarjo East of Java Indonesia. It is further termed as LUSI Mud Volcano (LUSI = Lumpur Sidoarjo; Lumpur mean mud in Indonesia language).

Mud, water, and gas extruded massively and flooded the surrounding areas. The mud flow currently covers an area of about 7 square-km, covering several villages. About 40,000 people have been displaced and the mud volcano is still active after more than 4 years.

The mud volcano seems to be unstoppable, and all the attempts to halt the mud eruptions have so far failed and never will be successfully perhaps.

The eruption of the LUSI mud volcano has triggered vertical (subsidence) and horizontal ground displacements. In the early development of mud volcano, GPS surveys results show that subsidence is occurring at rates of 0.1 and 4 cm/day surrounding the eruption area.

In the areas closest to the mud eruption, the results indicated the existence of horizontal concentric vector displacements and circular depressions of vertical vector displacements around the mud volcano which is expressing caldera formation processes.

Today its already four years and even more since the first time of the eruption, and the record of ground displacements inferred from several last GPS surveys showing exponential decay pattern. It is an interesting pattern of displacements we believed.

Since the displacement associated with the eruption, the exponential decay might be indicating or signing the ending of LUSI Mud volcano eruption. This paper will mainly explain these suggested situation in detail.

1. LUSI MUD VOLCANO

On May 29, 2006 a mud volcano started to form at Porong Sidoarjo East of Java Indonesia. It is further termed as LUSI Mud Volcano (LUSI = Lumpur Sidoarjo; Lumpur mean mud in Indonesia language). Mud, Water, and Gas extruded massively and flooding more than a kilometer areas. Since its extrusion day, the mud mixed water and gas has caused significant livelihood, environmental and infrastructure damages (Figure 1).

The volumes of erupted mud increased from the initial 5000 m3/day in the early stage to 120,000 m3/day in August 2006. Peaks of 160,000 and 170,000 m3 /day of erupted material follow earthquakes swarms during September 2006; in December 2006 the flux reached the record-high level of 180,000 m3/day; and in June 2007 the mud volcano was still expelling more than 110,000 m3/day (Manzzini et al., 2007). Latest information (after four years from eruption) showing 10,000 m 3/day erupted materials which is mostly dominated by water.

Figure 1 (a) LUSI mud volcano location, (b,c) LUSI mud volcano eruption, (d,e,f) scene of mud flooded, (g,h,i) map of flooded areas.

1.2 Ground Displacement at LUSI Mud Volcano

Considering the effects of mud loading, collapse of the overburden due to the removal of mud from the subsurface (eruption) and, land settlement caused by surface works (e.g. construction of dykes), etc., around LUSI mud volcano, ground displacements occurred immediately after the eruption.

Later on, the surface representation of displacement was also occurred such as crack on the wall, houses, street, bend on the rail ways, etc. On 24 November a gas pipeline exploded near the mud extrusion centre, killing several people. Part of ground displacement further may explained the caldera formation processes is happening on LUSI Mud Volcano (Andreas et.al, 2009, 2009a, 2010).

Caldera formation Processes is one of main processes of the birth and development of mud volcano. It Perform as a result of adaptation of subsurface extruded material (e.g mud, water, gas) to the surface following by surface collapse which is the next result performed typical morphology of caldera.

Some research clearly show the relationship between loss of volume in the shallow subsurface and caldera collapse (e.g. Acocella 2006; Aizawa et al. 2006; Geyer et al. 2006).

2. GPS OBSERVATION AND PROCESSING

GPS observations, both in campaign and continuous mode were conducted to study ground displacement phenomenon following the birth and development of LUSI mud volcano; among cooperation of some institutions.

Fifteen GPS campaigns have been conducted between June 2006 and December 2010. On figure 2 we can see some documentations of GPS surveys in the field.

GPS surveys were performed on up to about 50 stations with set area over 10 kilometers rounding the center of eruption, using dual-frequency geodetic-type receivers, with observation session lengths of about 5-10 hours.

GPS continuous subsidence monitoring was also conducted on some stations, started on 22 September 2006 to early 2007. Due to the change in mud coverage area, the numbers of observed GPS stations were different from survey to survey, and the observed stations could not always be the same.

Figure 2 Some documentation of GPS survey in the field using dual-frequency geodetic-type receivers, with observation session lengths of about 5-10 hours.

The locations of GPS stations were also restricted by the mud coverage and its progression.

Data processing of the GPS survey was conducted using the scientific GPS processing software Bernese 4.2 (Beutler et al., 2001). In general, standard deviations of the estimated coordinates are in the order of several mm in both horizontal and vertical components.

To derive the ground displacement information is simply by differencing the coordinates that has processed in each period of GPS surveys.

3. RESULT OF GROUND DISPLACEMENTS

3.1 First year result

The GPS derived displacements from the GPS campaigns showed that the surface displacements in the mud volcano area of Sidoarjo have both horizontal and vertical components.

In the first 4 months of mud extrusion it can be seen that the rates of displacements from data compilation and interpolation are in the order of 0,4 to 2,5 cm/day and increasing on the next 8 to 12 month later into 0,6 to 3,8 cm/day for vertical component surrounding the eruption site (see table 1).

According to other result (Abidin, 2008) in several month after LUSI eruption, the rates of horizontal and vertical displacements were up to 2 cm/day and 4 cm/day, respectively; and vertical displacements are dominated by subsidence.

Based on GPS results, the affected area of displacements up to end of August 2006 is contained to about 1 km around the extrusion centre. Starting from the third campaign, more GPS stations were observed.

Within this centimeter per day of displacement, will lead us to meters level of displacement in year time period (see table 1). Generally linier trend can be seen after several month from eruption up to a year time on the series of vertical displacement component on several GPS points investigation (figure 3).

GPS continuous that was set up in RW02 and RW01 between September 2006 and early 2007 give daily rate of vertical displacement or subsidence reached about 3.8 cm/day and 1.8 cm/day.

The results also show that about 7-8 months after the first mud extrusion, the subsidence around the main vent area exhibits a linear trend. The horizontal displacements of those two continuous stations are about 1.0 cm/day and 0.6 cm/day (Abidin, 2008). (see table1).

The reason that we found generally different characteristic of displacement among those spatial constrain. We conclude that displacement around inner caldera is associate with caldera formation processes and expressed by rapid subsidence characteristic (Andreas et.al, 2009, 2009a, 2010).

Figure 3 Graphic trend after several month from eruption up to a year time, on the series of vertical displacement component (in meter) on several GPS points investigation in LUSI area.

Meanwhile the rim and outer caldera has normal characteristic of subsidence which are most probably associate with the effects of mud loading, ground relaxation due to mud outflow, etc.

Figure. 4 (a) GPS model derived horizontal displacements (b) the vertical displacement given the model of cone subsidence, (c) Illustration of caldera formation processes on recently birth LUSI Mud Volcano.

A very much interesting to see from the first year ground displacement observation result, the pattern of horizontal displacement showed concentrate outlook toward the center of subsidence, meanwhile the vertical displacement given the model of cone subsidence (figure 4a, 4b).

This two information will shown good fact on explaining caldera formation processes that happening in LUSI mud volcano. Together with other information such as field surface representation of displacement, occurred buble plotting, micro seismic, etc. we can be sure that no doubt caldera formation is being develop in LUSI mud volcano (figure 4a).

3.2 After four years result

Table 2 Subsidence result after 4 year from eruption, and rates in 1,2,3,4 year from eruption TS02E - Land Deformation, 4901.

From the complete result of the whole GPS surveys (more than four years), unfortunately we were not getting the complete time series of ground displacement in every points of observations for the whole those time span of observation because of the change in mud coverage area that given the consequences to the number of observed GPS stations.

In this case the places and the numbers of observation were becoming different from survey to survey (the observed stations could not always be the same).

But, fortunately we still can made a model of the ground displacement based on interpolation and extrapolation.

So what happen after four years of the erruption turn out that the ground displacement has slowering at rates.

Its not 2-4 cm/day anymore but only several centimeter up to desimeter in a years time (table 2). A linier trend were replaced by exponential decay instead (figure 4).

Note that ground displacements (e.g. subsidence) around inner Caldera were un-identify after a year of eruption due to more likely chaotic grabben processes as part of caldera formation processes, plus mud coverage along with its loading effect has made observing or even after four years of Ground Displacements following LUSI Mud Volcano Eruption; Sign of its ending eruption extrapolating of ground displacements were nearly impossible.

In this case, we left blank information on such ground displacement processes around inner caldera after first year of eruption (table 2, figure 4). This first year assumption based on fact we fortunately still can observed displacement in some GPS points at inner caldera in this period (tabel1).

3.3 Sign of LUSI ending eruption?

Figure 5 Graphic trend after around four year time from eruption, on the series of vertical displacement component on several GPS points investigation in LUSI Mud Volcano area.

As mentioned previously, that the effects of mud loading, collapse of the overburden due to the removal of mud from the subsurface (eruption) and, settlement caused by surface works (e.g. construction of dykes), etc., leading to ground displacements around LUSI Mud volcano.

If the ground displacement decreasing in rates, it can be mean that factors derived them might timely disappear (e.g. ending of eruption).

If somehow that the ground displacement stopped, that mean that factors derived them might no longer exist (e.g. the mud eruption ended).

Fact has shown that after four years of the LUSI eruption turn out that the ground displacement has slowering at rates.

Its not 2-4 cm/day anymore but only several centimeter up to decimeter in a years time. A linier trend were replaced by exponential decay instead.

In this cased, this exponential decay might be indicating or signing the ending of LUSI Mud volcano eruption.

From the displacement projection result, after ten year period we will see rate generally 1-2 cm/years surrounding the eruption area which we can simply conclude that eruption may be ignored, and within twenty years we will see the rates generally less then cm/year which can be state that the eruption generally ended.

Seeing other research (Davies et.al, 2010) which made prediction of 26 years probabilistic longevity estimate for the LUSI mud volcano eruption, a very much similarity in the eruption time prediction found with our result (~20 years).

3 SUMMARY

GPS observations, both in campaign and continuous mode were conducted to study ground displacement phenomenon that following the birth and development of LUSI mud volcano.

The GPS derived displacements from the GPS campaigns showed that the surface displacements in the mud volcano area of Sidoarjo have both horizontal and vertical components.

The first 4 months of mud extrusion showed the rates of displacements (from data compilation and interpolation) are in the order of 0,4 to 2,5 cm/day and increasing on the next 8 to 12 month later into 0,6 to 3,8 cm/day for vertical component surrounding the eruption site.

After four years of the eruption turn out that the ground displacement has slowering at rates. Its not 2-4 cm/day anymore but only several centimeter up to decimeter in a year time.

A linier trend was replaced by exponential decay. Since the displacement associate with the eruption, the exponential decay might be indicating or signing the ending of LUSI Mud volcano eruption.

From the displacement projection result, after ten years period we can simply conclude that eruption may be ignored, and within twenty years from the first eruption we may state that the eruption is generally ended.

REFERENCES

Abidin, H.Z. , R.J Davies, M.A Kusuma, H. Andreas (2008), Subsidence and Uplift of Sidoarjo (East Java) due to the Eruption of the LUSI Mud Volcano (2006-Present) Environ Geol DOI 10.1007/s00254-008-1363-4

Acocella, V. 2006. Caldera types: how end-members relate to evolutionary stages of collapse. Geophysical Research Letters, 33, paper number L18314.

Aizawa, K., Acocella, V. & Yoshida, T. 2006. How the development of magma chambers affects collapse calderas: insights from an overview. In: Trosie, C., de Natale, G. & Kilburn, C.R.J. (eds) Mechanisms of Activity and Unrest at Large Calderas. Geological Society, London, Special Publications, 269, 65–81

Andreas H., H.Z.Abidin, M.A Kusuma, P. Sumintadireja, I. Gumilar. (2010), Ground Displacement around LUSI Mud Volcano Indonesia as Inffered from GPS Surveys; FIG Congress 2010 (Facing the Challenge-Building Capacity), , Sydney Australia, 11-16 April 2010.

Andreas H., H.Z.Abidin, M.A Kusuma, Irwan G.,T.Purnama Sidiq, M.Gamal (2009a), Caldera Formation Processes On LUSI Mud Volcano and Its Impact to People and Their Environment; The first International Conference on Sustainable Infrastructure and Built Environment in Developing Countries, Sabuga Institute of Technology Bandung, Bandung Indonesia, November 2-3, 2009

Andreas H., H.Z.Abidin, M.A Kusuma, Irwan G.,T.Purnama Sidiq, D.A Sarsito, M.Gamal (2009), Caldera Formation Processes On LUSI Mud Volcano; Procceding yearly seminar of HAGI (2009); (hard and digital copy), Jogjakarta, November 2009

Beutler, G., H. Bock, E. Brockmann, R. Dach, P. Fridez, W. Gurtner, U. Hugentobler, D.Ineichen, J. Johnson, M. Meindl, L. Mervant, M. Rothacher, S. Schaer, T. Springer, R.Weber (2001). Bernese GPS software version 4.2. , University of Berne, 515 pp

Davies, R.J, S.A Mathias, R. E. Swarbrick (2010). Probabilistic longevity estimate for the LUSI mud volcano, East Java, Journal of the Geological Society 2011; v. 168; p. 517-523

Geyer, A., Folch, A. & Marti, J. 2006. Relationship between caldera collapse and magma chamber withdrawal: an experimental approach. Journal of Volcanology and Geothermal Research, 157, 375–386

Mazzini,A., H. Svensen, G.G. Akhmanov, B. Istadi, S. Planke (2006) Pulsating and quasihydrothermal mud volcanism at LUSI, Indonesia; Geophysical Research Abstracts, Vol. 9, 09677, 2007 SRef-ID: 1607-7962/gra/EGU2007-A-09677 © European Geosciences Union 2007

BIOGRAPHICAL NOTES

Heri Andreas

Academic experience: Undergraduate. (Geodesy) Institute of Technology Bandung, Graduate.

(Geophysic) Institute of Technology Bandung, PhD. Student (Geodesy) Institute of Technology Bandung

Current position: Lecturer, Geodesy and Geomatic, Faculty of Earth Science and Technology, Institute of Technology Bandung Practical experience: GPS surveying and mapping, geodynamic-deformation and control surveys, boarder demarcation, Oil support engineering, site engineering

CONTACTS

Heri Andreas

Geodesy Research Division, Institute of Technology Bandung

LABTEX IXC Jl. Ganesha 10 Bandung 40132 – Indonesia

Telp /FAX : +62 22 253 4286 / +62 22 253 4286

Email: heri@gd.itb.ac.id