ANALYSIS AND INTERPRETATION OF TIME-LAPSE MICORGRAVITY DATA CASE STUDY IN KOTA LAMA SEMARANG TOURISM AREA

Supriyadi Supriyadi; Khumaedi Khumaedi; Sugiyanto Sugiyanto

doi:10.21009/SPEKTRA.053.02

Authors

Supriyadi Supriyadi Jurusan Fisika Universitas Negeri Semarang, Sekaran Gunungpati, Semarang, Indonesia
Khumaedi Khumaedi Jurusan Fisika Universitas Negeri Semarang, Sekaran Gunungpati, Semarang, Indonesia
Sugiyanto Sugiyanto Jurusan Fisika Universitas Negeri Semarang, Sekaran Gunungpati, Semarang, Indonesia

DOI:

https://doi.org/10.21009/SPEKTRA.053.02

Keywords:

microgravity, time-lapse, anomaly, Kota Lama, tourism area

Abstract

A time-lapse microgravity survey has been carried out in the Kota Lama (Semarang, Indonesia) tourism area. The survey in question is to measure gravity at the same point repeatedly with a specific time interval, in this case, conducted in January 2019 and July 2019. Measuring gravity is carried out at as many as 75 points that are spread evenly at the survey location. The instrument used is a Scintrex CG5 type gravimeter and GPS to determine the latitude and the longitude of each measuring point. The measurement results after being corrected, namely the Apungan and the Appeal correction, obtained the observational gravity (g_ob) in the January 2019 period showing that a minimum of 978118.44 mGal and a maximum gravity of 978118.88 mGal, while the minimum gravity measurement value in July 2019 showed a minimum of 978118.62 mGal and a maximum of 978118.88 mGal. Changes in the value (anomaly) gravity during the time interval, there are two possibilities, positive (0.02 to 0.29 mGal) and negative (-0.11 to -0.01 mGal). Both of these anomaly prices, if they are modeled, an anomaly source will be obtained, which is a positive anomaly caused by subsidence and a negative caused by changes in subsurface density related to dynamics (decrease or increase) of groundwater level.

References

[1] K. Mickus, K. (2003). Gravity method: environmental and engineering applications [Online]. Available: http://www.dot.state.fl.us/statematerialsoffice/Geotechnical/conference/materials/mickus.pdf.
[2] N. Darmawan et al., “Processing and data analysis of time-lapse microgravity due to ground water level changing in baseline stage of CO2 injection,” IOP Conf. Ser. Earth Environ. Sci., vol. 318, no. 1, 2019.
[3] S. Soedarsono and R. B. Arief, “Prediksi Amblesan Tanah (Land Subsidence) Pada Dataran Aluvial di Semarang Bagian Bawah,” in SEMINAR NASIONAL Kebijakan dan Strategi Pembangunan Infrastruktur Pengembangan Wilayah Berbasis Green Technology, pp. 2-9, 2012.
[4] M. Kobe et al., “Time-lapse gravity and levelling surveys reveal mass loss and ongoing subsidence in the urban subrosion-prone area of Bad Frankenhausen, Germany,” Solid Earth, vol. 10, no. 3, pp. 599-619, 2019.
[5] B. Yuwono and M. Awaluddin, “Land Subsidence monitoring 2016 - 2018 analysis using GNSS CORS UDIP and DinSAR in Semarang,” KnE Eng., vol. 2019, pp. 95-105, 2019.
[6] A. Setyawan et al., “Detecting Land Subsidence Using Gravity Method in Jakarta and Bandung Area, Indonesia,” Procedia Environmental Sciences, vol. 23, pp. 17-26, 2015.
[7] V. Pazzi et al., “Integrated geophysical survey in a sinkhole-prone area: Microgravity, electrical resistivity tomographies, and seismic noise measurements to delimit its extension,” Eng. Geol., vol. 243, pp. 282–293, 2018.
[8] S. Minardi and E. J. Wahyudi, “Analysis and Interpretation of Subsidence Source in Jakarta Using 2009-2010 Time-Lapse,” JTM, vol. 18, no. 4, 2011.
[9] Supriyadi et al., “Modeling response Time Lapse Microgravity Vertical Gradient (TLMVG) anomaly due to fluid volume changes of sub surface and its implementation in Kota Lama Semarang,” J. Phys. Conf. Ser., vol. 1321, no. 2, 2019.
[10] Supriyadi et al., “Strategy implementation time lapse microgravity method for monitoring subsidence,” AIP Conf. Proc., vol. 1818, March 2017.
[11] E. J. Wahyudi et al., “Designing a genetic algorithm for efficient calculation in time-lapse gravity inversion,” J. Eng. Technol. Sci., vol. 46B, no. 1, pp. 58-77, 2014.
[12] S. N. E. Wibowo, G. E. Mamuaya, and R. Djamaluddin, “Land Subsidence Analysis of Reclaimed Land using Time-Lapse Microgravity Anomaly in Manado, Indonesia,” Forum Geografi, vol. 32, no. 1, pp. 53-63, 2018.
[13] B. Tozer, A. B. Watts and M. C. Daly, “Crustal structure, gravity anomalies, and subsidence history of the Parnaíba cratonic basin, Northeast Brazil,” J. Geophys. Res. Solid Earth, vol. 122, no. 7, pp. 5591-5621, 2017.