Electronic Theses and Dissertation

ABSTRAK
Wilayah Pamir merupakan zona tektonik yang sangat aktif akibat konvergensi Lempeng India dan Eurasia. Penelitian ini bertujuan menginvestigasi pola geometri patahan secara detail di wilayah tersebut menggunakan data dari stasiun seismik lokal yang merekam gempa bermagnitudo kecil hingga menengah selama periode 2015-2017. Tahapan penelitian diawali dengan penentuan waktu tiba gelombang P dan S secara manual, dilanjutkan lokalisasi awal yang berhasil mendeteksi 862 hiposenter gempa. Lokalisasi ini kemudian direlokasi menggunakan metode Double-Difference (HypoDD). Relokasi ini secara signifikan meningkatkan akurasi lokasi hiposenter, ditandai dengan penurunan nilai Root Mean Square (RMS) menjadi di bawah 0,2 detik dan pengurangan jumlah kejadian gempa menjadi 721 hiposenter. Distribusi hiposenter hasil relokasi menunjukkan pola sebaran yang membentuk klaster rapat dan memanjang, yang secara jelas memetakan pola geometri struktur patahan utama di wilayah tersebut, yaitu Pamir Frontal Thrust, Darvaz Fault, dan Pamir Karakorum Fault. Analisis dari tiga irisan penampang vertikal (cross-section) dan mekanisme fokal mengonfirmasi kompleksitas geometri patahan di Pamir yang mencakup kombinasi sesar naik (reverse fault) dan sesar geser (strike-slip). Secara keseluruhan, metode ini terbukti efektif dalam memperjelas hubungan antara aktivitas seismik dengan detail geometri struktur geologi bawah permukaan di wilayah Pamir.

Kata kunci: Double-Difference, hiposenter, Pamir, geometri patahan.

ABSTRACT The Pamir region is a highly active tectonic zone resulting from the convergence of the Indian and Eurasian Plates. This study aims to investigate the detailed fault geometry patterns in the region using data from local seismic stations that recorded small- to moderate-magnitude earthquakes during the 2015–2017 period. The research began with the manual determination of P- and S-wave arrival times, followed by initial earthquake localization, which successfully detected 862 earthquake hypocenters. These hypocenters were subsequently relocated using the Double-Difference (HypoDD) method. The relocation significantly improved the accuracy of hypocenter locations, as indicated by the reduction of the Root Mean Square (RMS) value to below 0.2 seconds and the reduction in the number of earthquake events to 721 hypocenters. The distribution of the relocated hypocenters revealed clustered and elongated seismic patterns that clearly delineate the geometry of the major fault structures in the region, namely the Pamir Frontal Thrust, Darvaz Fault, and Pamir Karakorum Fault. Analysis of three vertical cross-sections and focal mechanisms confirmed the complexity of fault geometry in the Pamir region, which includes a combination of reverse faults and strike-slip faults. Overall, the Double-Difference method proved effective in clarifying the relationship between seismic activity and the detailed geometry of subsurface geological structures in the Pamir region. Keyword: Double-Difference, hypocenter, Pamir, fault geometry.