STUDI AKURASI CENTROID MOMENT TENSOR (CMT) PADA SOFTWARE JOKO TINGKIR DI WILAYAH KEPULAUAN MALUKU DENGAN PENDEKATAN SUDUT KAGAN DAN STATISTIKA INFERENSIAL

Jihan Nurrahma Wardani; Muhammad Nurul Fahmi; Madlazim

doi:10.26740/ifi.v14n3.p377-388

Authors

Jihan Nurrahma Wardani Universitas Negeri Surbaya
Muhammad Nurul Fahmi Universitas Negeri Surabaya
Madlazim

DOI:

https://doi.org/10.26740/ifi.v14n3.p377-388

Keywords:

Centroid Moment Tensor, Kepulauan Maluku, Sudut Kagan, Statistika Inferensial, Maluku Islands, Kagan Angle, Inferential Statistics

Abstract

Abstrak

Penentuan parameter mekanisme sumber gempa yang akurat sangat penting dalam kajian seismotektonik dan mitigasi bencana. Penelitian ini bertujuan untuk mengevaluasi keakuratan hasil inversi Centroid Moment Tensor (CMT) yang dihasilkan oleh perangkat lunak Joko Tingkir menggunakan pendekatan sudut Kagan dan analisis statistik inferensial, serta untuk mengkaji karakteristik sesar di wilayah Kepulauan Maluku. Penelitian dibatasi pada 25 kejadian gempa dengan magnitudo moment (M_w > 5) yang terjadi selama periode 2020 hingga 2024. Hasil perhitungan sudut Kagan menunjukkan bahwa seluruh data memiliki nilai dalam rentang 5° hingga 37°, berada jauh di bawah batas kritis 60° yang mengindikasikan tingkat kesesuaian tinggi antara Joko Tingkir dan katalog GCMT. Uji statistik parametrik menghasilkan nilai t untuk masing-masing parameter: strike (-0,431), dip (-0,164), rake (-0,991), latitude (-1,003), longitude (-0,205), dan depth (1,109), semuanya masih dalam rentang toleransi (±2,06). Nilai z-score untuk parameter M_w juga berada dalam batas wajar yaitu -1,883, tidak melampaui nilai kritis ±1,96. Dengan demikian, tidak ditemukan perbedaan signifikan secara statistik maupun visual antara kedua dataset. Selain itu, hasil inversi mengungkapkan bahwa wilayah Kepulauan Maluku didominasi oleh tiga tipe mekanisme patahan yaitu strike-slip, thrust, dan oblique reverse yang masing-masing berasosiasi dengan struktur aktif seperti Sesar Kawa, Banda Detachment, Snellius Ridge, dan Morotai Trough. Temuan ini mencerminkan dinamika tektonik yang kompleks akibat interaksi antara lempeng utama dan mikrolempeng di kawasan tersebut.

Abstract

Accurate determination of earthquake focal mechanism parameters is crucial for seismotectonic analysis and disaster mitigation. This study aims to evaluate the accuracy of Centroid Moment Tensor (CMT) inversion results generated by the Joko Tingkir software using the Kagan angle approach and inferential statistical methods, as well as to examine fault characteristics in the Maluku Islands region. The research is restricted to 25 earthquake events with a moment magnitude (M_w > 5) that occurred between 2020 and 2024. Kagan angle calculations indicate that all data pairs have values ranging from 5° to 37°, well below the critical threshold of 60°, suggesting a high level of similarity between Joko Tingkir and the GCMT catalogue. Parametric statistical tests yielded t-values for each parameter as follows: strike (-0.431), dip (-0.164), rake (-0.991), latitude (-1.003), longitude (-0.205), and depth (1.109), all within the acceptable range of ±2.06. The Z-score for the Mw parameter was -1.883, also within the critical range of ±1.96. These results indicate no statistically or visually significant differences between the two datasets. Furthermore, the inversion results reveal that the Maluku region is dominated by three faulting types: strike-slip, thrust, and oblique reverse, each associated with major active structures such as the Kawa Fault, Banda Detachment, Snellius Ridge, and Morotai Trough. These findings reflect the region’s complex tectonic dynamics resulting from interactions between major tectonic plates and microplates.

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