Surface Rupture Research Articles

Inferring 3D displacement time series through InSAR measurements and potential field theory in volcanic areas

Interferometric SAR (InSAR) techniques allow the detection of ground displacements along the satellite line-of-sight (LOS) directions. Moreover, InSAR can discriminate the ground deformations along the Up-Down and East-West by combining information gathered through ascending and descending paths. Conversely, the LOS-projected ground displacements remain less sensitive to the North-South components because almost all modern satellites fly along near-polar orbits. Our research aims to circumvent this limitation by developing a new method for reconstructing the 3-D ground displacement field in volcanic regions based on potential field theory and using InSAR measurements. We present the theoretical argumentations related to the developed method, demonstrating its efficacy through synthetic tests reconstructing the 3-D ground displacement field in elastic conditions. Then, we provide a 3-D ground displacement time series of the pre-eruptive displacement patterns related to the 2018 eruption at Sierra Negra volcano (Galapagos Archipelago, Ecuador). Our analysis revealed a maximum North-South displacement rate that increased from 40 cm/yr in the early pre-eruptive stage to 70 cm/yr before the eruption. The reliability of our results has been tested through comparison with Global Navigation Satellite System measurements. Our approach is innovative and represents a helpful tool for the investigation and modelling of volcanic sources.

Extensive off-fault damage around the 2023 Kahramanmaraş earthquake surface ruptures

Quantifying coseismic fault offsets for surface ruptures of major earthquakes is important for earthquake cycle and slip-rate studies, and thus for earthquake hazard assessments. However, measurements of such offsets generally underestimate fault slip due to inelastic deformation and secondary fault offsets, i.e., off-fault damage. Here, we use satellite synthetic aperture radar images to quantify off-fault damage in the two 2023 Kahramanmaraş (Türkiye) magnitude 7.8 and 7.6 earthquakes. We first derive three-dimensional coseismic surface displacements and show that on average ~35% of the coseismic slip is accommodated by off-fault damage within 5–7 km of the coseismic surface ruptures. Fault sections exhibiting geometrical complexities (e.g., bends and step-overs) experienced a higher level of off-fault damage than simpler fault sections. Our results highlight the importance of extending off-fault damage assessments to several km away from fault ruptures and indicate that fault offset measurements may underestimate slip-rate estimations by as much as a third.

The Central Mindoro Fault: An Active Sinistral Fault Within the Translational Boundary Between the Palawan Microcontinental Block and the Philippine Mobile Belt

The NNW-trending Central Mindoro Fault (CMF) is an active oblique left-lateral strike-slip fault as determined from offset morphotectonic features such as spurs and streams. Mapping of the trace and determination of the sinistral strike-slip sense of motion of the CMF is essential not only to the assessment of hazards but also to providing a clearer perspective of its role in accommodating deformation resulting from the NW relative motion between the Philippine Sea Plate and the Sunda Plate. Its sense of motion is also kinematically congruent with the NW-SE translation along a transcurrent zone between the Philippine Mobile Belt and the Palawan Microcontinental Block on the western part of the Philippine archipelago. It is also consistent with the left-lateral motion of other structures within the zone, such as the Verde Passage Fault—another structure believed to be accommodating the NW-SE translation. Mapping of the CMF provides a key constraint in identifying the possible mechanism(s) involved in the dextral strike-slip motion of the 1994 Mindoro Earthquake ground rupture, which is subparallel to the CMF.

Determination of present-day crustal deformation along the Kenyan rift system using InSAR

The Kenyan rift system is prone to deformation due to various geological processes and human activities, such as overexploitation of groundwater and exploitation of geothermal energy. Crustal deformation monitoring is essential for understanding the geodynamics of the rift and assessing potential hazards as the rift passes through densely populated areas. However, retrieving InSAR displacement measurements along the Kenya rift system is challenging due to the high variability in tropospheric delay caused by its location in the tropics and the significant topographic variations along the rift. Here, we leverage Sentinel-1 data to analyze both local and large-scale deformation in the rift using multi-temporal InSAR processing with an improved tropospheric correction method, which we previously proposed with a modification on variance covariance modeling. We provide evidence for the previously reported ground displacement of 5-7.5 cm southwest of the Suswa volcano as being a misidentification of a tropospheric delay, that was dominant on March 27, 2018. Moreover, we observe episodic ground displacement at Suswa and Longonot, attributable to magma movement. Our results indicate that Suswa experienced a 9 cm movement towards the satellite line of sight between 2018-2020, while Longonot moved 4 cm towards satellite line of sight between 2016-2018 and also underwent 3 cm displacement away from the satellite line of sight between 2019-2021. In addition, we observe land subsidence associated with geothermal exploitation in the range of 1-3.6 cm/yr in Olkaria as well as in multiple locations in Nairobi at a rate of up to 6 cm/yr, primarily attributed to groundwater overexploitation. Moreover, we detect undocumented ground displacement at the Chalbi salt flat and along the Elgeiyo escarpment, at rates of up to 4.8 cm/yr and 5.7 cm/yr, respectively. Long-wavelength, low-amplitude deformation at the Turkana depression aligned well with the current kinematics of the Kenyan rift system. We find that localized deformations, caused by magmatism and human activity, dominate the south segment of the rift, whereas large-scale low-amplitude deformations dominate the north segment. In summary, our results emphasize the importance of tropospheric delay correction in retrieving InSAR-derived displacement measurements along the Kenyan rift system.Graphical

Complexity of near-surface deformation and subsurface structure of the Chihshang creeping fault-line scarp, eastern Taiwan: insights from integration of geological and geophysical data

The precise position and geometry of a fault and the recognition of contemporary active strands are pivotal elements for formulating regulations for earthquake fault zones and fault setbacks. The western frontal escarpment toe of the Coastal Range in Tapo, eastern Taiwan is commonly considered as the plausible location of the N18°E-trending, east-dipping Chihshang creeping seismogenic fault. Frontal collapse and flattening of reverse faulting, in addition to fluviation and landslide have complicated the process for defining the Chihshang fault configuration. We used a multidisciplinary approach, combining site investigation, geological core analysis and correlation, resistivity prospecting, and inclinometer monitoring, to illuminate the subsurface structure and deformation of the leading edge of the Chihshang fault at Tapo Elementary School. We found that (1) the Chihshang main fault is a contact of alluvium deposits and the mudstone of Lichi mélange, and has a dip angle of approximately 77° within the resistivity gradation zone 55 m east of the toe of the geomorphic escarpment; (2) it has a 2-year cumulative horizontal displacement of 20.7 mm northwestward and continuously creeps without seasonal variation; and (3) the active deformation on the escarpment results from a combined effect of fault creeping and slow gravity sliding of the mass which is steadily supplied by the Chihshang reserve faulting. A mechanism of faulting-relay landsliding is proposed to understand the active deformation on the escarpment. Great caution is needed in the interpretation of the aseismic surface ruptures along the inferred trace of reverse creeping faults as fault branching.Graphical

Investigating Deformation and Failure Mechanisms of Discontinuous Anti-dip Bench Rock Slopes Through Shaking Table Tests and Numerical Simulations

Abstract Large-scale shaking table tests and numerical simulations were conducted to investigate the deformation and failure mechanisms of an anti-dip bench rock slope with discontinuities. The study introduces the Displacement Baseline Offset Ratio (DBOR) to characterize the instability and failure processes of slopes when they reach a plastic state under seismic excitations. It examines the peak ground displacement and earth pressure responses, as well as the cumulative damage processes of the slope model to provide insight into the deformation and failure mechanisms. The results show a significant displacement amplification effect at elevated points of the slope when subjected to seismic excitations. Furthermore, as the input frequency of the sine wave increases, the amplitude of the displacement response at the upper part of the slope accelerates. The widest bench divides the entire slope into smaller segments, hindering the deformation and failure across the benches and reducing stress transfer from the upper slope, thereby preventing stress concentration at the toe of the slope. The distribution of DBOR suggests that plastic deformation is more pronounced on the inner side of the bench than on the outer side, leading to earlier cracking on the inner side. A critical displacement threshold for seismic damage of each bench is established based on residual displacement responses and critical peak acceleration. These findings provide theoretical references for the risk assessment and seismic design of bench rock slopes.

Determining the Parameters of Gurson–Tvergaard–Needleman Model for Predicting the Failure of Wrought and Fused Filament Fabricated 17-4 PH Stainless Steel

Abstract Metal additive manufacturing is an emerging technology for creating metallic parts, with metal fused filament fabrication (FFF) rapidly gaining popularity due to its cost-effectiveness. Despite the acceptable mechanical properties of additively manufactured metals using FFF, a significant technical challenge is the presence of undesirable porosity, which affects material performance. This study aims to model the material behavior of FFF 17-4 PH stainless steel, considering its porosity, using the Gurson–Tvergaard–Needleman (GTN) damage model. The GTN model, which incorporates the micromechanical behavior of ductile metals, shows great potential for failure prediction. The GTN model parameters were identified for both wrought and FFF 17-4 PH stainless steel through a series of proposed methods. Initial void volume fractions were determined using density measurements. The evolution of void volume fractions was experimentally assessed through interrupted uniaxial tensile tests, leading to the analytical derivation of three void nucleation parameters based on continuum damage mechanics. Additional GTN model parameters related to material failure were determined through microscopic analysis of rupture surfaces and finite element (FE) trial-and-error methods. FE simulations using the GTN damage model, represented as porous metal plasticity in abaqus, were conducted to verify the identified parameters. The results demonstrated that the numerical calculations of the FE model are in good agreement with the experimental data. The use of experimentally derived GTN model parameters from the proposed methods effectively predicts material behavior, particularly in the post-necking region where traditional FE modeling fails to simulate the realistic material response.

Tracing the relationship between the upper plate earthquake cycle and megathrust slip, the Atacama fault system in Northern Chile

Inland-normal faulting is recognised as an important process following large subduction earthquakes. The lack of data limits the understanding of how normal fault reactivation relates to the subduction earthquake cycle. We characterised the palaeoseismology of the Atacama fault system (AFS) in the Chilean subduction zone. Our results showed that upper plate normal faulting earthquakes with Mw 7.0 and recurrence intervals of 35 ± 9 ky generated surface ruptures preserved as fault scarps. The average fault slip rate of 0.07 ± 0.01 m/kyr is three orders of magnitude slower than the convergence velocity, and the recurrence intervals of surface-rupturing earthquakes on the studied faults are much larger than the recurrence of great to giant (Mw > 8.5) subduction earthquakes in the Chilean margin. This demonstrates that the reactivation of an individual fault in the AFS is not always synchronised with this type of subduction earthquake.

Near-Fault Tilted Deformation of Buildings Associated with Coseismic Surface Ruptures in the Shenxigou Section, 2008 Mw 7.9 Wenchuan Earthquake, Eastern Tibet

Near-Fault Tilted Deformation of Buildings Associated with Coseismic Surface Ruptures in the Shenxigou Section, 2008 Mw 7.9 Wenchuan Earthquake, Eastern Tibet

Analysis of co-seismic ionospheric disturbance of the Qinghai Mw 7.4 earthquake on May 21, 2021

ABSTRACT In this study, the total electron content (TEC) was extracted from Global Navigation Satellite System (GNSS) data provided by the Crustal Movement Observation Network of China (CMONOC). The ionospheric disturbances related to the Qinghai earthquake on 21 May 2021 were analysed. Significant coseismic ionospheric disturbances (CIDs) were observed near the earthquake epicentre. To further investigate the propagation characteristics of ionospheric anomalies associated with this earthquake, the epicentral area was divided into eight regions, each corresponding to a 45° sector, to analyse the characteristics of ionospheric disturbances. Firstly, based on the spatial and temporal characteristics of the slant total electron content, different degrees of ionospheric disturbances were identified at various time intervals after the earthquake. Secondly, the earthquake generated two types of coseismic ionospheric disturbances at the epicentre. The first type, with velocities of approximately 1.4 km s− 1, 1.8 km s− 1, and 1.0 km s− 1, were triggered by acoustic waves generated by the ground surface rupture induced by the earthquake. The second type, with velocities of about 0.8 km s− 1, represented another form of ionospheric disturbance induced by acoustic waves from the ground surface rupture. Thirdly, the ionospheric anomaly was most pronounced within the 90°–135° sector relative to the epicentre, corresponding to the southeast direction from the epicentre. Finally, based on the data from 15 GNSS stations at the epicentre, the coseismic deformation displacement of the earthquake was determined, with a maximum displacement of 0.24 m, and the leptokurtic slip characteristics of the earthquake were revealed.

The focal mechanism and field investigations of mining-induced earthquake by super-thick and weak cementation overburden strata fracturing

Mining-induced earthquake (MIE) is a non-natural earthquake induced by mining activities. In Ordos mining area, super-thick and weak cementation overburden strata (STWCS) are common occurrence in Jurassic coal seam overlying strata. To explain and quantify the focal mechanism and roof fracture characteristics of MIE under the STWCS, the surface subsidence, ground borehole televiewer imaging and microseismic monitoring technologies were used to observe the fracturing of STWCS. The relative moment tensor method was also used to explore quantify focal mechanism of MIE. The results show that the development height of rock fractures increases, and the STWCS start to break when the panel below retreats along goafs. During this period, the surface stepped subsidence increases rapidly, and MIEs with magnitude above 2.0 begin to appear. The inversion matrix is constructed with the relative moment tensor method to solve the source mechanism of coal mining microearthquakes. The matrix improves the inversion efficiency and accuracy, thus being suitable for solving the focal mechanism of MIE by roof breaking. When coal seam is mined under the STWCS, the dip angle of focal rupture surface is mainly between 0° and 30°, accounting for about 50% of the total. The seismic source is mainly featured with roof horizontal separation tension and roof rotation compression instability. During mining along goafs, the seismic sources displayed a tendency of upward expansion and the shear slip ruptures were more than that in the solid coal mining stage. The focal mechanism of the MIEs in Shilawusu Coal mine was caused by the primary and periodic tension rupture of the STWCS and shear slip rupture. With the continuous mining of the panel, there is still the possibility of another round of MIEs. The research results provide a reference for the prediction, risk assessment and disaster control of MIEs under extremely thick overburden strata.

Determination of Anatolian Plate’s tectonic block boundaries with clustering analysis using GNSS sites velocities

The Anatolian Plate is an important tectonic structure containing different types of faults. In this study, block boundary studies were performed by clustering analysis using horizontal velocity data for 841 GNSS sites located on the Anatolian Plate. Four algorithms were used to determine the most appropriate cluster number. Cluster analysis was performed with K-means analysis. Different to other studies, the analysis included the location parameter for the GNSS sites in the cluster analysis. Generally block boundaries followed active fault zones and surface ruptures forming as a result of earthquakes. In this block study, 3 previously undocumented block boundaries were defined based on GNSS data. When all parameters are assessed in cluster analysis, the most appropriate cluster number was determined to be 9.

The 2020 Mw 6.4 Koryak Highlands earthquake illustrates hidden seismic hazards in the northern Pacific Cordillera

SUMMARY On 2020 January 9, an Mw 6.4 earthquake struck the central Koryak Highlands of eastern Siberia, northeast of the diffuse triple junction between the North American, Pacific and Eurasian plates. The largest earthquake recorded in the central Koryak Highlands to date, it provides an excellent opportunity to study the little-known active tectonics of this remote, sparsely instrumented region. We mapped coherent, coseismic surface deformation with Sentinel 1 Interferometric Synthetic Aperture Radar (InSAR), making this one of the highest latitude earthquakes to be captured successfully with satellite radar, in spite of the rugged, snow-covered terrain. Elastic dislocation modelling, teleseismic backprojections, calibrated hypocentral relocations and teleseismic moment tensor solutions are used to resolve a left-lateral fault trending northwestwards, proximal but perpendicular to a regional geological suture zone, the Khatyrka–Vyvenka Thrust. The earthquake probably ruptured unilaterally northwestwards along a 20 km long segment that appears indistinct in the local topography, and likely generated no surface rupture. We interpret that these observations are indicative of a structurally immature fault zone and estimate a seismogenic zone thickness of 10–15 km. The Koryak Highlands earthquake illustrates how terrane boundaries within cordilleran belts may continue to accommodate tectonic strain long after accretion, resulting in significant earthquakes even along hidden faults.

Step characteristics and formation mechanism of strike slip faults in Wuerhe asphalt vein, Junggar Basin

In order to define the geometric characteristics, formation mechanism and fault wall movement direction of steps about mini-extensional shear strike-slip fault zone in Wuerhe asphalt vein. Field outcrop observation, 3D seismic data interpretation, fracture formation time and stress mechanism analysis were carried out. There is no friction in the vein section and the initial fracture shape is maintained. Not only negative steps but also steps is developed, and even steps and negative steps coexist in a cross section. The step is the microtension rupture surface associated with the strike-slip fault plane, which does not have the pointing significance of the fault wall relative movement. The outcrop features are typical, which overturns the consensus of domestic and foreign scholars based on the structural physics simulation experiments that the small steepness generated at the early stage of normal fault, reverse fault and strike-slip fault sections are all negative steps.

Detection of ionospheric disturbances with a sparse GNSS network in simulated near-real time Mw 7.8 and Mw 7.5 Kahramanmaraş earthquake sequence

On February 6, 2023 the Kahramanmaraş Earthquake Sequence caused significant ground shaking and catastrophic losses across south-central Türkiye and northwest Syria. These seismic events produced ionospheric perturbations detectable in Global Navigation Satellite System (GNSS) total electron content (TEC) measurements. This work aims to develop and incorporate a near-real-time (NRT) ionospheric disturbance detection method into JPL’s GUARDIAN system. Our method uses a Long Short-Term Memory (LSTM) neural network to detect anomalous ionospheric behavior, such as co-seismic ionospheric disturbances among others. Our method detected an anomalous signature after the second Mw 7.5 earthquake at 10:24:48 UTC (13:24 local time) but did not alert after the first Mw 7.8 earthquake at 01:17:34 UTC (04:17 local time), which had a visible disturbance of smaller amplitude likely due to lower ionization levels at night and potentially the multi-source mechanism of the slip.Plain Language Summary Seismic activity, including the destructive Kahramanmaraş Earthquake Sequence on February 6, 2023 in the Republic of Türkiye, result in vertical ground displacement that cause atmospheric waves. These waves propagate upwards to the outer atmosphere, disturbing the ionospheric electron content. This disturbance impacts the signals broadcast by positioning satellites (such as GPS) and received by ground-based receivers. If the receiver position is known, the impact to these signals can be used to measure the electron density disturbance caused by these seismically-induced atmospheric waves. Such studies usually rely on being aware of the event a priori. Using deep learning neural networks, we instead aim to detect anomalous signals automatically. We propose to utilise this method to detect seismically-induced disturbances over a large geographical area. The detection method proposed in this paper successfully detected an anomalous event in the ionosphere approximately ten minutes after the second earthquake in the Kahramanmaraş Earthquake Sequence.

Aftershocks on the Planar Rupture Surface of the Deep-Focus Mw 7.9 Bonin Islands Earthquake

Aftershocks on the Planar Rupture Surface of the Deep-Focus Mw 7.9 Bonin Islands Earthquake

Evaluation of Residual Phase from Orbit Accuracy Using TerraSAR-X/TanDEM-X SAR Observation

Interferometric synthetic aperture radar (InSAR) is used to observe precise surface displacement and create digital elevation models by calculating the phase differences between two or more SAR images obtained over the same surface area. The phase of a repeat-pass interferogram can be expressed as the sum of contributions from topography, ground displacement, earth curvature, noise, and the satellite’s orbital phase component. For precise observations, removing unnecessary phase components is essential. Errors owing to the satellite’s orbit accuracy leave residual phases in the interferogram, which become a significant limitation for wide-area ground displacement monitoring using the InSAR technique. This study used four pairs of images acquired by TerraSAR-X in monostatic pursuit mode from October 2014 to February 2015 to analyze the residual phase caused by orbital errors. Since these images were acquired with a 10-second interval between the TerraSAR-X and TanDEM-X satellites, the phase coherence was maintained over time. The Tarim Basin in China was selected as the study area to minimize the impact of terrain distortion. By introducing a 0.5 m error into the x, y, and z components of the satellite position vectors and creating differential interferograms, it was found that the x component’s orbital error caused the largest residual phase, with linear residual phases observed in the north-south direction. Furthermore, various baselines ranging from -29.71 to 263.21 m were used to quantitatively compare the residual phases caused by orbital errors based on the perpendicular baseline. The residual phase was similar across the four differential interferograms, with approximately 3.49 π for the x component, 0.85 π for the y component, and 1.25 π for the z component. The residual phase resulting from simulated orbital errors was effectively mitigated using a 2D quadratic model.

Rocking Spectrum for Cylindrical Structures Subjected to Bidirectional Pulse‐Like Ground Motions

ABSTRACTIn recent years, cylindrical structures free to rock have been exploited in practical engineering. However, their seismic response in three dimensions (3D), greatly sensitive to the parameters that define it, is difficult and time‐consuming to predict. To this end, this study focuses on developing a rocking spectrum, an efficient graphical tool linking seismic rocking response to structural parameters, for seismic response prediction and performance‐based seismic design of cylindrical structures. The development of the rocking spectrum is based on the numerical rocking response of 2500 idealized rigid cylinders excited by 100 sets of synthetic bidirectional pulse‐like ground motions. The minimum Redundancy Maximum Relevance (mRMR) algorithm is first employed to reveal that the rocking response is more related to ground acceleration, ground velocity, and ground displacement when the response is small (close to uplift), intermediate, and large (close to overturning), respectively. Following these relations, the support vector machine (SVM) algorithm is employed to develop the rocking spectrum. The obtained rocking spectrum can reliably predict the rocking response of cylinders subjected to the synthetic pulse‐like ground motions. The applicability of the spectrum is also discussed for as‐recorded pulse‐like ground motions.

Conditional probability of surface rupture: A numerical approach for principal faulting

This study presents a numerical approach for probabilistic fault displacement hazard analysis (PFDHA), aimed at addressing an alternative solution with commonly used empirical methodologies. Our model utilizes probability distributions to compute the conditional probability of surface rupture (CPSR). Leveraging earthquake catalogs, we derived the hypocentral depth distribution (HDD) across eight globally distributed seismotectonic regions categorized by faulting kinematics (normal, reverse, strike-slip). We calculated the hypocentral depth ratio (HDR) distribution, to model rupture position from the hypocenter. Employing magnitude scaling relations we determined rupture widths (W) spanning magnitudes 5–8. User-input parameters, including fault style, average dip angle, and seismogenic depth, with associated uncertainties, derive the CPSR estimation of surface rupture occurrences. Our findings highlight seismogenic depth as the most influential parameter and reveal correspondences between empirical curves derived for specific regions, emphasizing the importance of site-specific rupture probability assessments over global datasets and underscores the significance of considering seismotectonic context when evaluating fault displacement hazard. The numerical code for CPSR calculation has been developed and is openly accessible on GitHub.

Earthquake Moment Magnitudes from Peak Ground Displacements and Synthetic Green's Functions

Earthquake Moment Magnitudes from Peak Ground Displacements and Synthetic Green's Functions