18 research outputs found
Imaging of Complex Earthquake Ruptures: Bayesian Source Inversion and Seismic Network Optimization
No full textUnderstanding the earthquake rupture process is critical for constraining seismic hazard and advancing knowledge of fault behavior. Earthquake rupture may range from relatively simple to inherently complex, particularly for large earthquakes, with complexity governed by fault geometry and heterogeneous stress conditions, making its estimation by inversion challenging. Inversion of rupture parameters from surface observations remains an ill-posed problem, strongly dependent on noise in the data, observational resolution, unknown subsurface properties, and modeling assumptions. This dissertation addresses these challenges by integrating an advanced Bayesian framework for finite fault inference, backprojection imaging, a quantitative comparison technique, and seismic network optimization to improve the resolution and reliability of rupture imaging. The first study investigates the 2021 Mw7.4 Maduo earthquake in Qinghai, China, which ruptured a previously unmapped fault. Bayesian finite-fault inversion of teleseismic and geodetic data, complemented by back-projection imaging, resolves a bilaterally propagating rupture with asymmetric complexity. Comparison across published slip models shows that differences in assumed fault geometry and inversion strategy produce substantial variability in slip models and Coulomb stress transfer, underscoring how model uncertainties may influence interpretations. The second study examines the 2023 Mw7.8 and Mw7.6 Türkiye earthquake doublet. A Bayesian inversion of static GPS, InSAR, strong-motion, and teleseismic data reveals rupture across a geometrically complex, multi-segment fault. The Mw7.8 event ruptured bilaterally with sustained subshear velocities, while the Mw7.6 event transitioned between subshear and supershear. Variability among single-dataset and joint inversions highlights limited data resolution and emphasizes the value of integrating diverse observations. This study further demonstrates that geometric barriers control rupture termination and complexity. The third study explores seismic monitoring strategies for the Gulf of Aqaba, where station deployment is restricted to the Saudi Arabian margin. Synthetic tests show that station distribution and azimuthal coverage are more critical than array shape or density. Practical line arrays positioned at scaled distances relative to fault and rupture length can adequately capture rupture parameters under one-sided observational constraints. Together, these studies demonstrate the value of uncertainty quantification for reliable rupture characterization, highlight the sensitivity of stress-transfer estimates to slip-model variability and the sensitivity of slip models to different datasets and fault geometry, and establish principles for network design in regions with limited azimuth coverage
ALTERNATIF PEMODELAN NUMERIK KOPEL THERMO-HYDRO -MECHANIC INJEKSI CO2 PADA FORMASI GEOLOGI BAWAH PERMUKAAN
No full textCO2 injection into subsurface formations is a potential method to reduce CO2 gas emissions in the atmosphere. Geological and geophysical studies are carried out as an effort to analyze the storage capacity and potential risks. The results are then used to analyze the response of reservoir rock to the injected CO2 fluid. The effect of fluid injection on reservoir rocks is complex and involves a coupled system of fluid flow-geomechanics. CO2 fluid injection can increase fluid pressure that affects the local stress conditions of reservoir and surrounding rock. Meanwhile, changes in temperature due to the presence of CO2 fluid also affect reservoir rock stress, although not significantly. The complexity of the subsurface reservoir system includes thermomechanical and hydromechanical analysis involving multi-phase and multi-component fluids. To study these complex interactions, a program which can simulate the coupling between multi-phase and multi-component fluid-flows-geomechanics is needed. To accommodate these needs, Rutqvist et al (2002) have proposed a numerical modeling approach by linking TOUGH2-ECO2N and FLAC3D. In this study we developed an external program that linking TOUGH2 with different fluid modul (ECO2M), and FLAC3D using these approaches to run the coupled THM simulation automatically and seamlessly until the end of simulation
Identifikasi Struktur Geologi dan Petrografi di sekitar Observatorium Astronomi Lampung Gunung Betung
No full textLampung Astronomical Observatory (LAO) is located on Betung Mountain which is quite close to the Semangko active fault zone. Betung Mountain is part of the Bukit Barisan which is located west of the city of Bandar Lampung. This mountain has an altitude of about 1200 meters above sea level. There are 6 interesting stations. Most of the stations are located on the upper slopes of Betung Mountain. In the Talang Aji area, there are 2 springs. The other 4 stations consist of waterfalls with varying heights: Talang Teluk waterfall (30 m), Talang Rabun waterfall (20 m), Betung waterfall consists of two minor terraced waterfalls with a height of 5 and 10 m respectively, and Kubu Jambu waterfall (12 m). In general, the orientation of the faults of Mt. Betung was northeast-southwest. The faults are also associated with several waterfalls found in the field. From the joint data processing, it can be interpreted that the fault formed on Betung Mountain is normal. The lithology of Betung Mountain is dominated by volcanic deposits in the form of tuffs. In certain rivers, there are outcrops of lava igneous rock in the form of Andesites. Andesite lava in the northern and southern parts of Betung Mountain has different characteristics
Ambient Noise-Based Mapping of Bedrock Morphology and Potential Fissure Zone in East Tanjung Karang, Bandar Lampung, Lampung, Indonesia
No full textAs a business center and the most populous subdistrict, East Tanjung Karang in Bandar Lampung, Lampung, Indonesia, is considered an area with excessive groundwater exploitation. This activity can trigger ground fissures that can consequently cause damage to buildings and roads. In this study, microtremor recordings from 17 sites were collected and analyzed by using the horizontal to vertical spectral ratio and ellipticity curve method. Results showed that the ground profiles of shear wave velocity from 17 sites ranged from 143.5 m/s to 1752.46 m/s, and they could be used to determine sediment layer and its thickness based on the SNI 1726-2012 criteria. The thickness of the bedrock varied from 8.18 m to 117.18 m. Bedrock morphology was obtained by subtracting the sediment thickness from the altitude value. The bedrock morphology and slope were then used to construct a potential fissure map of the area between Y16 and Y17 and between Y26 and Y27, which had high bedrock slopes (more than 45°). The ground fissure potential in these areas was higher than that in other areas. Such areas also had a geological hazard potential from ground fissures caused by excessive groundwater exploitation. Our study could be used by authorities as a basis for preventing subsidence-related disasters in this subdistrict
Automatic Event Identification From Tectonic Earthquakes with Modified Akaike Information Criterion (mAIC)
No full textSupershear Rupture of the 1995 Mw 7.2 Multi-Segment Nuweiba Earthquake in the Gulf of Aqaba
No full textThe Gulf of Aqaba (GoA) is the seismically most active region in the Red Sea, with a history of large earthquakes and posing a high seismic hazard to coastal communities. This study uses back-projection and dynamic rupture simulation to investigate the largest instrumentally recorded earthquake in GoA, the 1995 Mw7.2 Nuweiba earthquake to understand stress loading, failure mechanisms, and cascading rupture potential on complex multi-segment fault systems. Our results indicate a multi-segment rupture and supershear on the Aragonese Fault, optimally oriented to the regional stress. Supershear rupture significantly amplified offshore ground shaking, elevating seismic hazard for the narrow gulf’s coastal regions. This event partially ruptured the fault system, increasing Coulomb stress on the unbroken southern Arnona Fault, which has been silent since 1588. This stress loading likely advanced a future rupture on this critical segment, requiring close monitoring and increased preparedness for a potential large earthquake in the region.This work was supported by King Abdullah University of Science and Technology (KAUST, grants BAS/1/1339-01-01 and RGC/3/6036-01). TU and AAG acknowledge additional support from Horizon Europe (ChEESE-2P, grant number 101093038, DT-GEO, grant number 101058129, and Geo-INQUIRE, grant number 101058518), the National Aero415 nautics and Space Administration (80NSSC20K0495), the National Science Foundation (grant numbers EAR-2225286, EAR-2121568, OAC-2139536, OAC-2311208, OAC-2311206) and the Statewide California Earthquake Center (SCEC awards 22135, 23121). We gratefully acknowledge the KAUST Supercomputing Laboratory (https://www.hpc.kaust.edu.sa/) for providing computing resources on the Shaheen II in projects k1587 and k1589, and Shaheen III in project K10043, the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for providing us with computing time on the supercomputer SuperMUC-NG at the Leibniz Supercomputing Centre (www.lrz.de) in projects pr63qo, pn49ha and the Institute of Geophysics of LMU Munich (Oeser et al., 2006)
Bayesian Inversion and Quantitative Comparison for Bilaterally Quasi-Symmetric Rupture Processes on a Multi-Segment Fault in the 2021 Mw7.4 Maduo Earthquake
No full textSummary
On May 21st, 2021, the Mw7.4 Maduo earthquake occurred in the southern Qinghai Province, China. This earthquake ruptured approximately 160 km along the Kunlunshankou-Jiangcuo fault, an east-west trending fault located in the middle of the Bayan Har Block (BHB). The seismogenic fault exhibits an apparent simple geometry, characterized by fault branches to the east and a splay fault to the west. Despite the apparent simplicity of the fault’s structure, a noteworthy level of variability and inconsistencies persist in the representations of fault geometry in published rupture models of the earthquake. Our study employs a Bayesian approach to elucidate both the fault geometry and kinematic rupture parameters of the earthquake. We use three-dimensional displacements obtained from synthetic aperture radar (SAR) images and teleseismic data to quantify the rupture kinematics. We then conduct three separate finite-fault inversions (FFI) using individual datasets, and perform a subsequent joint inversion for a comprehensive analysis. Additionally, we employ teleseismic backprojection (BP) to complement the kinematic analysis of the earthquake rupture. Both kinematic finite-fault inversion and backprojection unveil a nearly symmetric bilateral rupture in the east-west direction, characterized by an average rupture speed of approximately 2.7 km/s. The rupture to the east displays a heightened level of complexity, manifested in at least five discernible stages, whereas the rupture to the west is comparatively simpler. The eastward rupture directly triggered the southern branch of the bifurcating fault, with a notable delay of approximately 3 s on the northern branch. Several studies have presented coseismic slip models for the earthquake. An analysis of variability among 10 slip models, including our preferred model, highlights that fault geometry and inversion strategy (e.g., fault discretization, smoothing factor) contribute to considerable variability in both slip magnitude and slip extent on the fault, despite similar data types being used in the inversions. Furthermore, the finite-fault model acquired through slip inversion plays a crucial role in calculating Coulomb failure stress change (ΔCFS) transmitted from the source fault to neighboring receiver faults. Understanding how the variability in slip models influences ΔCFS calculations is essential for conducting comprehensive analyses in seismic hazard studies. Our findings highlight that discrepancies in fault geometry contribute to the variance of ΔCFS in the regions delineating positive and negative stress change. Meanwhile, variability in slip magnitude substantially impacts the variability of ΔCFS in the vicinity of the source fault. Furthermore, our analysis of ΔCFS calculations using our preferred slip models indicates that a major event on the Maqin-Maqu segment, a well-recognized seismic gap on the East Kunlun Fault (EKF), could potentially be advanced in time.We express gratitude to the anonymous reviewers and the editor, Prof. Ana M. G. Ferreira, for providing constructive comments that contribute to the improvement of this manuscript. The research presented herein received support from the King Abdullah University of Science and Technology (KAUST) under grant BAS/1/1339-01-01
Supershear Rupture of the 1995 Mw 7.2 Multi-Segment Nuweiba Earthquake in the Gulf of Aqaba
No full textThe Gulf of Aqaba (GoA) is the seismically most active region in the Red Sea, with a history of large earthquakes and posing a high seismic hazard to coastal communities. This study uses back-projection and dynamic rupture simulation to investigate the largest instrumentally recorded earthquake in the GoA, the 1995 7.2 Nuweiba earthquake, to understand stress loading, failure mechanisms, and cascading rupture potential on complex multi-segment fault systems. Our results reveal a multi-segment cascading rupture with supershear rupture on the optimally prestressed Aragonese Fault. Supershear rupture significantly amplified offshore ground shaking, elevating seismic hazard for the narrow gulf's coastal regions. This event partially ruptured the GoA fault system, increasing Coulomb stress on the unbroken southern Arnona Fault, which has been silent since 1588. This stress loading likely advanced a future rupture on this critical segment, requiring close monitoring and increased preparedness for a potential large earthquake in the region.We sincerely thank Editor Germán Prieto and the two anonymous reviewers for their insightful comments, which have greatly contributed to improving this manuscript. This work was supported by King Abdullah University of Science and Technology (KAUST, Grants BAS/1/1339-01-01 and RGC/3/6036-01). TU and AAG acknowledge additional support from Horizon Europe (ChEESE-2P, Grant 101093038, DT-GEO, Grant 101058129, and Geo-INQUIRE, Grant 101058518), the National Aeronautics and Space Administration (80NSSC20K0495), the National Science Foundation (Grants EAR-2225286, EAR-2121568, OAC-2139536, OAC-2311208, OAC-2311206) and the Statewide California Earthquake Center (SCEC awards 22135, 23121). We gratefully acknowledge the KAUST Supercomputing Laboratory (https://www.hpc.kaust.edu.sa/) for providing computing resources on the Shaheen II in projects k1587 and k1589, and Shaheen III in project K10043, the Gauss Centre for Supercomputing e.V. (www.gauss-centre.eu) for providing us with computing time on the supercomputer SuperMUC-NG at the Leibniz Supercomputing Centre (www.lrz.de) in projects pr63qo, pn49ha and the Institute of Geophysics of LMU Munich (Oeser et al., 2006)
Rupture dynamics and velocity structure effects on ground motion during the 2023 Türkiye earthquake doublet
No full textAbstract Earthquake doublets defy typical aftershock patterns, challenging seismic hazard assessment. Understanding their rupture dynamics and interactions is crucial for advancing earthquake forecasting and hazard analysis. The destructive February 6, 2023, earthquake doublet of magnitudes 7.8 and 7.6 rocked south-central Türkiye and northwestern Syria. Here, we investigate ground motion characteristics through dynamic rupture modeling, revealing intricate rupture evolution driven by a 3D complex fault system and a rotational stress regime. Our models, validated by interferometric synthetic aperture radar, global navigation satellite system, local strong motion, and teleseismic data, reliably reproduce the observed shaking. Synthetic ground motions show directivity-driven amplification during subshear rupture, whereas supershear rupture elevates ground-motion levels off the fault but mitigates directivity amplification. Ground-shaking patterns are further affected by 3D Earth structure and topographic effects, and exhibit distance-decaying peak-ground velocity (1 Hz resolution) consistent with observations and empirical expectations. Our results highlight the value of integrating physics-based rupture simulations to enhance seismic hazard assessment
Seismic gap breached by the 2025 Mw 7.7 Mandalay (Myanmar) earthquake
No full textSeismic gaps are fault sections that have not hosted a large earthquake for a long time compared to neighbouring segments, making them likely sites for future large events. The 2025 Mw 7.7 Mandalay (Myanmar) earthquake, on the central section of the Sagaing Fault, ruptured through a known seismic gap and ~160 km beyond it, resulting in an exceptionally long rupture of ~460 km. Here we investigate the rupture process of this event and the factors that enabled it to breach the seismic gap by integrating satellite synthetic aperture radar observations, seismic waveform back-projection, Bayesian finite-fault inversion and dynamic rupture simulations. We identify a two-stage earthquake rupture comprising initial bilateral subshear propagation for ~20 s followed by unilateral supershear rupture for ~70 s. Simulation-based sensitivity tests suggest that the seismic gap boundary was not a strong mechanical barrier in terms of frictional strength, and that nucleation of the earthquake far from the gap boundary, rather than its supershear speed, allowed the rupture to outgrow the gap and propagate far beyond it. Hence, we conclude that the dimension of seismic gaps may not reflect the magnitude of future earthquakes. Instead, ruptures may cascade through multiple fault sections to generate larger and potentially more damaging events.This work was supported by King Abdullah University of Science and Technology (KAUST, grant no. BAS/1/1339-01-01 to B.L., C.S. and P.M.M.). We acknowledge the KAUST Supercomputing Laboratory for providing computational resources on Shaheen III under project K10043. D.L. acknowledges funding from the New Zealand Ministry of Business, Innovation and Employment through the National Seismic Hazard Model Science Programme (contract no. 110316). Y.K. acknowledges funding from the European Research Council (ERC) under the BE_FACT project (grant no. 101142339)
