The coastal area of ​​Demak is composed of alluvial plains influenced by the presence of coastal deposits. The alluvial area has materials such as silt clay, grained clay, medium sand, silty sand, silt, clay, and sediment. Knowledge of soil structure and modulus of elasticity in the coastal area of the ​​Demak Regency is essential to determine the potential of aquifers in an area. Research using the HVSR (horizontal to vertical spectral ratio) microtremor method was conducted to determine the potential for aquifers beneath the ground surface in the Demak Coastal area. Data collection was carried out at 89 points for 10 minutes using a 3-component TDS type 303S seismograph and a sampling rate of 20 Hz. Microtremor data were processed using Excel, Geopsy, and Dinver software to obtain the v_s and Poisson ratio parameters. The difference between aquicludes can be determined by combining the v_s value with the Poisson's ratio. The value of v_s < 350 m can describe the presence of soft clay, stiff clay and silt structures, while the Poisson’s ratio describes the saturation of the material. Aquifers can be found with a combination of values ​​ranging from 350 < v_s < 1500 m and the Poisson's ratio > 0.3. Potential aquifers with saturated clay aquicludes are found at stations 5, 57 and 73, while unsaturated clay aquicludes are found at station 61. Potential aquifers with silt aquicludes are found at stations 14, 60, 71, 38 and 34.

Keywords: Microtremor, HVSR, Aquifer, the Poisson's ratio, v_s, the Coastal Demak, groundwater

REFERENCES

American Society of Civil Engineers (2017) Minimum design loads and associated criteria for buildings and other structures (ASCE/SEI 7–16), ASCE. http://doi.org/10.1061/9780784414248

Arintalofa V, Yuliyanto G, Harmoko U (2020) Subsurface characterization of Diwak Derekan geothermal field by HVSR analysis method based on microtremor data. AIP Conference Proceedings, 2296(1). https://doi.org/10.1063/5.0030356

BPS Demak Regency (2020) Demak Regency in figures. BPS Demak Regency. Demak

Das BM (1993) Principles of geotechnical engineering. 3rd edn. PWS Publishing Company, Boston

Herak M (2008) Model HVSR-A matlabs tool to model horizontal to vertical spectral ratio of ambient noise. Journal Computer and Geosciences 34(11): 1514–1526. https://doi.org/10.1016/j.cageo.2007.07.009

Irham MN, Zainuri M, Yuliyanto G, Wirasatriya A (2021) Measurement of ground response of Semarang coastal region risk of earthquakes by Horizontal to Vertical Spectral Ratio (HVSR) microtremor method. IOP Publishing Journal of Physics: Conference Series, 1943(1):012033. http://doi.org/10.1088/1742-6596/1943/1/012033

Keçeli A (2012) Soil parameters which can be determined with seismik velocities. Jeofizik 16:17–29

Lay T, Wallace TC (1995) Modern global seismology. Academic Press, USA, p 521

Mulyono P (1996) Quaternary geological map of the Demak Plate, Java, Bandung. Center for Geological Research and Development

Nakamura Y (1989) a method for dynamic characteristics estimation of subsurface using mikrotremor on ground surface.  Q. Rep. RTRI Railw Tech Res Inst 30(1):25-33

Nakamura Y (2000) Clear identification of fundamental idea of Nakamura’s technique and its applications. The 12th World Conference on Earthquake Engineering, Auckland, New Zealand, 30 January-4 February 2000, p 2656

Nurwidyanto MN, Harmoko U, Gernowo R et al (2024) Analysis of earthquake vulnerability of the Demak coastal area based on the HVSR (horizontal to vertical spectral ratio) method. Indonesian Journal of Applied Physics 14(2). https://doi.org/10.13057/ijap.v14i2.90703

Nurwidyanto MN, Zainuri M, Wirasatriya A, Yuliyanto G (2023) Microzonation for earthquake hazards with HVSR microtremor method in the coastal areas of Semarang, Indonesia. Geographia Technica 18(1):177–188. http://doi.org/10.21163/GT_2023.181.13

Rahmawan LE, Yuwono BD, Awaluddin M (2016) Monitoring survey of land surface deformation in coastal areas using GPS measurement method in Demak Regency in 2016. Jurnal Geodesi Undip 5(4):44–55 (in Indonesian)

Santosa DPP, Hadian MSD, Zakaria Z (2021) Hydrostratigraphy and aquifer geometry in Palu Groundwater Basin, Central Sulawesi Province after earthquake. Jurnal Sumber Daya Air 17(1):25–38. https://doi.org/10.32679/jsda.v17i.695 (in Indonesian)

Telford WM, Telford WM, Geldart LP (1990) Applied Geophysics. Cambridge University Press, Cambridge, p 792. https://doi.org/10.1017/CBO9781139167932

Thanden RE, Sumadiredja H, Richards PW et al (1996) Geological map of the Magelang and Semarang Sheets, Jawa. Geological Research and Development Centre. Bandung, Indonesia

Trihatmoko E, Wiguna HS, SanjotoTB et al (2020) Preliminary research on seawater intrusion in Sriwulan Village, Demak, Indonesia. Indonesian Journal of Oceanography 2(4):396-402. https://doi.org/10.14710/ijoce.v2i4.9304 (in Indonesian)

Yulianto T, Yuliyanto G (2023a) Microtremor data and HVSR method in the kaligarang fault zone Semarang, Indonesia. Data In Brief 49(109428). https://doi.org/10.1016/j.dib.2023.109428

Yuliyanto G, Yulianto T (2023b) Microtremor data and HVSR method of geothermal manifestation of Mt. Telomoyo, Central Java, Indonesia. Data In Brief 51:109721. https://doi.org/10.1016/j.dib.2023.109721

Yuliyanto G, Harmoko U, Widada S (2017) Identify the slip surface of land slide in Wirogomo Banyubiru Semarang Regency using HVSR method. Int J Appl Environ Sci 12:2069–2078

Yuliyanto G, Nurwidyanto MI (2021) Integrated survey to identify potential groundwater aquifers in Jabungan Semarang using geoelectric and microtremor methods. IOP Publishing Journal of Physics: Conference Series 1943(012026). http://doi.org/10.1088/1742-6596/1943/1/012026

Yuliyanto G, Nurwidyanto MIN, Harmoko U et al (2025) Aquifer zone delineation using correlation between microtremor methods and geoelectricity, ANAS Transactions 1:79–88. https://doi.org/10.33677/ggianas20250100143