Aceh Int. J. Sci. Technol., 11(3) 258-265 December 2022 doi: 10.13170/aijst.11.3.28818 Copyright: © 2022 by Aceh International Journal of Science and Technology 258 Ground Surface Quality Assessment Using P-wave Velocity from 2-D Seismic Refraction Method Zul Fadhli 1* , Sabrian Tri Anda 2 ,Muhammad Syukri 3,* , Moehammad Ediyan Raza Karmel 4 , Alfi Sunny Tutifla 1 , Purwandy Hasibuan 5 , and Rini Safitri 3 1 Geophysics Engineering Department of Engineering Faculty of Syiah Kuala University, 23111, Indonesia 2 Physics Department, Engineering Faculty, Universitas Samudra, 24416, Indonesia 3 Physics Department of Mathematics and Science Faculty of Syiah Kuala University, 23111, Indonesia 4 Mining Engineering Department of Engineering Faculty of Syiah Kuala University, 23111, Indonesia 5 Civil Engineering Department of Engineering Faculty of Syiah Kuala University, 23111, Indonesia *Corresponding author: zulfadhli@unsyiah.ac.id Received : November 29, 2022 Received in revised from January 28, 2023 Accepted : January 31, 2023 Online : January 31, 2023 Abstract – A good strength level of the ground surface is the main concern in an area with rapid housing infrastructure development, such as Baitussalam district-Aceh Besar, Indonesia. A seismic refraction method was applied with three similar profile lines using PASI 16S – 24P equipment and 10 Hz vertical geophones to identify the sub-surface layer. The result was processed using Winsism software and Surfer 8. The results of seismic refraction were deduced and correlated with conventional geotechnical investigation obtained by a previous study. The results of 3 survey lines show that the area has two main layers. The first layer was interpreted as overburden (soil and clayey sand) with a compressional wave velocity (Vp) value of fewer than 1.8 km/s. The second layer produces a high velocity of more than 2 km/s. This second layer is interpreted as highly to moderately weathered rock. The results of seismic refraction surveys of the present study suggest a reasonably good correlation with the standard penetration test (SPT) and rock quality designation (RQD) obtained in the previous investigation. The strength level of the second layer showed N-SPT of 65 and RQD of at least 50%. Keywords: seismic refraction, compression wave velocity, N-SPT, RQD. Introduction As science keeps evolving, especially in the civil and environmental engineering disciplines, the involvement of geophysics as a problem-solving approach has allowed a new subset of geophysics, particularly applied geophysics or geophysical engineering. The term geophysical engineering can be interpreted as the application of geophysical methods to investigate subsurface material to explain subsurface conditions, in which the results would have significant implications for engineering science (Reynolds, 2011). The involvement of geophysical methods in civil and environmental engineering aims to broaden knowledge and accommodate the rapid development of urban areas in various countries. The traditional method, such as the borehole method, is considered less effective in determining subsurface conditions even though it can accurately describe subsurface conditions (Mohamad et al., 2015). The lack of efficiency is due to longer measurement time, destructive nature, and limited coverage with high application cost (Massarch, 2000). The application of geophysical methods in civil and environmental engineering varies greatly, from determining the “rippability” of rock and the depth of scour around bridge pilings, providing soil-strength estimates for dams and building foundations to predicting liquefaction zone (Steeples, 2001, Syukri et al., 2020, Soupios et al., 2007, Abidin et al., 2007, Lai, 2018). However, major problems in both engineering disciplines could not be solved and explained solely by geophysical methods. Determining the appropriate geophysical method also enables the researchers to minimize errors during data interpretation. For example, the seismic method is the most suitable geophysical method for engineering or environmental site investigation because the