Solo, 13 - 16 October 2014

“Micro Earthquake Survey Design, Optimization with modeling”

“PIT2014-1022”

Name : Firman Syaifuddin

Date/Place of Birth : 11-09-1984/ Jakarta

Institution / Afiliation : Institut Teknologi Sepuluh Nopember (ITS)

Educations Background : - Master Degree at Teknik Geofisika

Institut Teknologi Bandung (ITB)

- Undergraduate Degree at Geofisika Meteorologi

Institut Teknologi Bandung (ITB)

PIT HAGI Solo 2014

PIT HAGI Solo 2014

PIT HAGI Solo 2014

Exploration geothermal is one important things in

geothermal industry.

Geophysical prospect generation commonly use potential

and electrical method as preliminary survey.

MicroEarthquake survey used as tools for monitoring effect

of injection well in development stage

MEQ survey can be uses as validation and verification of

our geothermal reservoir geometry or body in the

exploration stages.

Possible to optimizing MEQ survey to get better data with

survey design and modeling the best location of our tools

to record the MEQ event related to the hydrothermal

system in geothermal plays.

PIT HAGI Solo 2014

PIT HAGI Solo 2014

PIT HAGI Solo 2014

PIT HAGI Solo 2014

What kind information given by microearthquakes records in the

geothermal/ hydrothermal system :

• Fracture structure map by seismicity

• Hydrologic structure details defined

• Induced seismicity affected by man made activities (i.e injection.)

PIT HAGI Solo 2014

The identification of micro

earthquakes (MEQ) with Richter

magnitude range: 1 to 3 in a

prospective geothermal area is a

means to investigate and characterize

modern tectonic activity and volcanic

areas.

Such activity is frequently related to

major hydrothermal convection

systems including active faulting and

fracturing in the subsurface, and also

the base of the brittle/ductile transition

above a heat source (Ward, 1972;

Wright et al., 1985; Manzella, 2000;

Chan, 2013).

PIT HAGI Solo 2014

• Station Distribution

For an effective microearthquake network (permanent or temporary), which can

provide reliable data for earthquake location, the station sites should be evenly

distributed by azimuth and distance. The maximum azimuthal gap between the

stations should be less than 180°, and the distance between the stations should not

be more than twice the average focal depth of the earthquakes. Optimal distribution of

stations has been studied by Sato and Skoko (1965) and Uhrhammer (1980),

• Site Selection

There are various constraints in site selection, which affect station distribution If

seismic noise is high, benefit of modern instrument is lost and poor detection will

result. If stations are situated on soft ground, even Broad Band or very broadband

records will be useless and Short Period responses will not be interpretable due to

local noises.

PIT HAGI Solo 2014

PIT HAGI Solo 2014

Hydrothermal convection systems creates seismic source.

Seismic velocity and Resistivity has good correlation (faust 1951).

Our resistivity data extracted from MT survey have good quality.

Seismic wave modeling used 2D elastic wave modeling in lateral

average velocity model

PIT HAGI Solo 2014

Resistivity data Velocity model

Velocity-Resistivity correlation

Random points/ locations (Site Selection)

Possible source position identification

Seismic wave propagation

modeling

Seismic wave simulation parameters

Seismogram analysis

The best station locations

(Faust, 1951)

PIT HAGI Solo 2014

PIT HAGI Solo 2014

Resistivity – Velocity correlation

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Near surface velocity map

Averaging Velocity 0-1500m

PIT HAGI Solo 2014

PIT HAGI Solo 2014

PIT HAGI Solo 2014

PIT HAGI Solo 2014

PIT HAGI Solo 2014

• Based on our evaluation in arrival time separation between p-wave and s-wave, from 20

stations the stations which well recorded data is only 7 stations. The separation of P-S

wave range from 0.314 to 0.924 with lateral distance from 914 to 2447 m from the center

geyser location or MEQ source simulated.

• The distribution of well recorded data stations relatively uniform, 4 stations in the eastern

part of fault and 3 stations in the western part of fault. The best location of the stations

shows in figure above, black dot shows all the stations, and the black dot covered by red

dot circle.

• In figure before shows seismogram resulted from seismic wave simulation, that give

information about which station location the saparation of P and S arrival time. If in the real

MEQ survey use only 4 stations, from this result, I suggest to use the stations location

number 1, 6, 8 and 9 to cover the possible MEQ source location associated with geyser or

hydrothermal activity and fault.

• In this study evaluation only used P-S wave separation as tool to analyzed, for better

knowledge and more useful information we have to modeled in 3 dimension and use

attenuation property that effecting the recording quality of the data. This algorithm still to

be tested to the real survey to get better conclusion.

PIT HAGI Solo 2014

• To get better data quality of MEQ survey, we have to get more information

about subsurface condition in our field for designing the survey where to put our

sensor location as recording stations.

• Used electrical property information from magnetotelluric (MT) survey can be

very useful to built preliminary velocity model as an input to simulating the

propagation of seismic wave triggered by MEQ around geyser or hydrothermal

activity in the geothermal prospect field.

PIT HAGI Solo 2014

PIT HAGI Solo 2014

References

• Chang, J. S. H., 2013, MSc Thesis, Department of Physics, University of Alberta.

• Faust, L. Y., 1951, Geophysics, v. 18, p. 271-288.

• Mukuhira, Y., Asanuma, H., Niitsuma, H., Haring, M., Deichmann, N., 2010, GRC

Transactions, Vol. 34, p. 407-412.

• Onacha, S., Kahn, D., Malin, P., Shalev, E., 2005, GRC Transactions, Vol. 29, p. 497-502.

• Pramono, B., Colombo, D., 2005, Proceedings World Geothermal Congress 2005,

Antalya, Turkey.

• Tim Geofisika terpadu, 2009, Pusat Sumber Daya geologi, Badan Geologi.

• Warr, P. L., 1972, Geothermics, Vol. 1, No.1, p.3-12.

• Kayal, J.R., 2008, Microearthquake Seismology and Seismotectonics of South Asia

• Warpinski, N.R., 2011, Microseismic Source Mechanisms Must Be Understood Before

Results Can be Accurately Interpreted.

PIT HAGI Solo 2014

Station-00

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Station-01

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