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Stress Transfer and Seismicity Along the Southern Great Sumatran Fault: Insights from the 1994 Liwa Earthquake.

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Title: Stress Transfer and Seismicity Along the Southern Great Sumatran Fault: Insights from the 1994 Liwa Earthquake.
Alternate Title: Prijenos naprezanja i seizmičnost duž južnoga Velikog sumatranskog rasjeda: uvidi iz potresa u Liwi 1994.
Authors: Kurniawan, Andri1 andrikurniawan@eng.unila.ac.id, Silaen, Nicolas2, Ibrahim, Khalil2, Nurrochman, Arsy1, Destawan, Ridho1, Maulida, Nanda Hanyfa1, Prasetyo, Irfan2, Zaenudin, Ahmad1, Wibowo, Adhi3
Source: Rudarsko-Geološko-Naftni Zbornik. 2026, Vol. 41 Issue 3, p99-113. 15p.
Subject Terms: *Strains & stresses (Mechanics), *Earthquakes, *Seismic migration, *Geologic faults, *Earthquake hazard analysis, *Paleoseismology, *Shearing force
Abstract (English): The February 15, 1994 Mw 6.8 Liwa earthquake ruptured the southern Great Sumatran Fault (GSF), yet its static stress legacy and relation to subsequent seismicity remain weakly quantified. We integrate high-precision double-difference relocation with Coulomb failure stress (△CFS) modelling to evaluate post-1994 stress transfer along the Semangko sector. Using ~16,000 P/S picks and identical inversion settings, we test two 1-D velocity models; CRUST1.0 yields near-zero, narrow differential-time residuals (± 0.3-0.4 s) compared with broader heavy tails for AK135 (± 0.7-0.8 s) and are adopted for the final catalogue. Since phase archives are sparse before 2010, events from 1994 - 2009 are treated as background, whereas 2010-2024 earthquakes are relocated; quality control retains 416 events. Relocation suppresses the artificial ~10 km depth band and collapses epicenters into coherent clusters that delineate the West/East Semangko Faults and Semangko Bay. △CFS was computed for depths of 5-20 km and µ' = 0.2-0.8. All scenarios produce the expected four-lobed right-lateral pattern with maxima >0.10 MPa around WSF-B, ESF-A, and the Kumering Fault. Relocated events preferentially occupy positively loaded regions: ~74% fall at △CFS > 0 and ~73% at △CFS = 0.01 MPa (10 kPa), robust to µ' and depth. The results indicate unresolved post-1994 loading on multiple Semangko branches and adjacent segments, highlighting the potential for cross-segment triggering. We advocate expanding seismic and geodetic monitoring and targeted paleoseismic surveys in the Semangko-Kumering corridor to refine recurrence estimates and update physicsbased hazard models for southern Sumatra. [ABSTRACT FROM AUTHOR]
Abstract (Bosnian): Potres u Liwi magnitude 6,8 koji se dogodio 15. veljače 1994. godine prekinuo je južni Veliki sumatranski rasjed (GSF), no statička naprezanja zaostala nakon potresa i njihova povezanost s naknadnom seizmičnošću ostaju slabo kvantificirani. U ovome istraživanju integrira se visoko precizna dvostruko razlikovna realokacija s modeliranjem Coulombova naprezanja (△CFS) kako bi se procijenio prijenos naprezanja nakon 1994. godine duž sektora Semangko. Koristeći ~16,000 P/S odabira i ista prilagođavanja inverzije, testiraju se dva 1-D modela brzine; CRUST1.0 daje gotovo nulte, uske diferencijalne vremenske reziduale (± 0.3 - 0.4 s) u usporedbi sa širim raspodjelama s izraženim „repovima" za AK135 (± 0.7 - 0.8 s) te se usvaja za konačni katalog. Budući da su arhive faza oskudne prije 2010. godine, događaji od 1994. do 2009. tretiraju se kao pozadinski, dok se potresi od 2010. do 2024. realociraju; kontrola kvalitete zadržava 416 događaja. Realokacija suprimira umjetnu dubinsku traku od ~10 km i grupira epicentre u koherentne skupine koje ocrtavaju zapadne/istočne rasjede Semangko i zaljev Semangko. △CFS je izračunan za dubine od 5 do 20 km i µ' = 0,2 - 0,8. Svi scenariji proizvode očekivani četverorežanjski desni lateralni uzorak s maksimumima >0,10 MPa oko WSF-B, ESF-A i rasjeda Kumering. Realocirani događaji preferencijalno zauzimaju pozitivno opterećena područja: ~74 % pada na △CFS > 0 i ~73 % na △CFS = 0,01 MPa (10 kPa), robusno prema µ' i dubini. Rezultati upućuju na neriješeno opterećenje nakon 1994. na više grana Semangka i susjednim segmentima ističući potencijal za aktiviranje između segmenata. Predlaže se proširenje seizmičkoga ili geodetskoga nadzora i ciljanih paleoseizmičkih istraživanja u koridoru Semangko-Kumering kako bi se precizirale procjene ponavljanja i ažurirali fizički modeli opasnosti za južnu Sumatru. [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
Description
Abstract:The February 15, 1994 Mw 6.8 Liwa earthquake ruptured the southern Great Sumatran Fault (GSF), yet its static stress legacy and relation to subsequent seismicity remain weakly quantified. We integrate high-precision double-difference relocation with Coulomb failure stress (△CFS) modelling to evaluate post-1994 stress transfer along the Semangko sector. Using ~16,000 P/S picks and identical inversion settings, we test two 1-D velocity models; CRUST1.0 yields near-zero, narrow differential-time residuals (± 0.3-0.4 s) compared with broader heavy tails for AK135 (± 0.7-0.8 s) and are adopted for the final catalogue. Since phase archives are sparse before 2010, events from 1994 - 2009 are treated as background, whereas 2010-2024 earthquakes are relocated; quality control retains 416 events. Relocation suppresses the artificial ~10 km depth band and collapses epicenters into coherent clusters that delineate the West/East Semangko Faults and Semangko Bay. △CFS was computed for depths of 5-20 km and µ' = 0.2-0.8. All scenarios produce the expected four-lobed right-lateral pattern with maxima >0.10 MPa around WSF-B, ESF-A, and the Kumering Fault. Relocated events preferentially occupy positively loaded regions: ~74% fall at △CFS > 0 and ~73% at △CFS = 0.01 MPa (10 kPa), robust to µ' and depth. The results indicate unresolved post-1994 loading on multiple Semangko branches and adjacent segments, highlighting the potential for cross-segment triggering. We advocate expanding seismic and geodetic monitoring and targeted paleoseismic surveys in the Semangko-Kumering corridor to refine recurrence estimates and update physicsbased hazard models for southern Sumatra. [ABSTRACT FROM AUTHOR]
ISSN:03534529
DOI:10.17794/rgn.2026.3.7