IDENTIFICATION OF SUBSURFACE ROCKS IN GEOTHERMAL AREA OF NORTH TAPANULI USING HORIZONTAL TO VERTICAL SPECTRAL RATIO METHOD. EINSTEIN (e-Journal), [S. l.], v. 14, n. 1, p. 47–55, 2026. DOI: 10.24114/b1bd4b60. Disponível em: https://jurnal.unimed.ac.id/2012/index.php/einsten/article/view/64966. Acesso em: 24 apr. 2026.