Maximum Slip Research Articles

Effect of curing conditions on mode-II debonding between FRP and concrete: A prediction model

The rehabilitation and strengthening of concrete structures using Fiber-Reinforced Polymer (FRP) materials have been widely investigated. As a priority issue, however, the effect of curing conditions on the bonding behavior between FRP and concrete structures is still elusive. This study aims at developing a prediction model to accurately capture the mode-II interfacial debonding between FRP strips and concrete under different curing conditions. Single shear debonding experiments were conducted on FRP-concrete samples with respect to different curing time t and temperatures T. The J-integral formulation and constrained least square minimization are carried out to calibrate the parameters, i.e., the maximum slip s- and stretch factor n. The prediction model is developed based on the cohesive model and Arrhenius relationship. The experimental data are then analyzed using the proposed model to predict the debonding between FRP and concrete, i.e., the interfacial shear stress-slip relationship. A Finite Element (FE) model is developed to validate the theoretical predictions. Satisfactory agreements are obtained. The prediction model can be used to accurately capture the bonding performance of FRP-concrete structures.

Two‐Phase Exhumation of the Santa Rosa Mountains: Low‐ and High‐Angle Normal Faulting During Initiation and Evolution of the Southern San Andreas Fault System

AbstractLow‐angle detachment fault systems are important elements of oblique‐divergent plate boundaries, yet the role detachment faulting plays in the development of such boundaries is poorly understood. The West Salton Detachment Fault (WSDF) is a major low‐angle normal fault that formed coeval with localization of the Pacific‐North America plate boundary in the northern Salton Trough, CA. Apatite U‐Th/He thermochronometry (AHe; n = 29 samples) and thermal history modeling of samples from the Santa Rosa Mountains (SRM) reveal that initial exhumation along the WSDF began at circa 8 Ma, exhuming footwall material from depths of >2 to 3 km. An uplifted fossil (Miocene) helium partial retention zone is present in the eastern SRM, while a deeper crustal section has been exhumed along the Pleistocene high‐angle Santa Rosa Fault (SFR) to much higher elevations in the southwest SRM. Detachment‐related vertical exhumation rates in the SRM were ~0.15–0.36 km/Myr, with maximum fault slip rates of ~1.2–3.0 km/Myr. Miocene AHe isochrons across the SRM are consistent with northeast crustal tilting of the SRM block and suggest that the post‐WSDF vertical exhumation rate along the SRF was ~1.3 km/Myr. The timing of extension initiation in the Salton Trough suggests that clockwise rotation of relative plate motions that began at 8 Ma is associated with initiation of the southern San Andreas system. Pleistocene regional tectonic reorganization was contemporaneous with an abrupt transition from low‐ to high‐angle faulting and indicates that local fault geometry may at times exert a fundamental control on rock uplift rates along strike‐slip fault systems.

Strain partitioning in Southeastern Alaska: Is the Chatham Strait Fault active?

A 1200 km-long transform plate boundary passes through southeastern Alaska and northwestern British Columbia and represents one of the most seismically active, but poorly understood continental margins of North America. Although most of the plate motion is accommodated by the right-lateral Queen Charlotte–Fairweather Fault (QCFF) System, which has produced at least six M>7 earthquakes since 1920, seismic hazard assessments also include the Chatham Strait Fault (CSF) as a potentially active, 400 km-long strike slip fault that cuts northward through southeastern Alaska, connecting with the Eastern Denali Fault. Nearly the entire length of the CSF is submerged beneath Chatham Strait and Lynn Canal and has never been systematically imaged using high-resolution marine geophysical approaches. In this study we present an integrated analysis of new marine seismic reflection data acquired across Lynn Canal and tectonic block modeling constrained by data from continuous and campaign GPS sites. Seismic profiles cross the CSF at twelve locations spanning ∼50 km of fault length; they reveal thick (up to 300 m) packages of glaciomarine sedimentary facies emplaced on an unconformity surface that formed during the Last Glacial Maximum (LGM). Localized warping of post-LGM stratigraphy (∼13.9 kyr B.P. to present) appears to correlate with sediment drape on basement topography and current-controlled deposition. There is no evidence for an active fault along the axis of Lynn Canal in the seismic reflection data. Crustal block models constrained by GPS data allow, but do not require, a maximum slip rate of 2–3 mm/yr along the CSF; higher slip rates on the CSF result in significant misfit to GPS data in the surrounding region. Based on the combined marine geophysical and GPS observations, it is plausible that the CSF has not generated resolvable coseismic deformation in the last ∼13 ka and that the modern slip-rate is <1 mm/yr. We propose that models for strain transfer between the QCFF and the Denali Fault, and seismic hazard maps in general, may need to be reevaluated.

Source Process of the October 2016 Tottori-Chubu Earthquake(&lt;i&gt;M&lt;/i&gt;j 6.6) and Relation with Near Source Strong Motions

A source process inversion for an Mj 6.6 earthquake which occurred on October 21, 2016 in central Tottori Prefecture, was performed using near-field strong motion waveforms. The results showed that a left-lateral strike-slip component was dominant on the fault plane, the strike of which was in a NNW-SSE direction and the dip almost vertical. The moment magnitude was estimated as 6.2. A large slip area (asperity) was determined around the hypocenter, including its northern shallow part, in which the maximum slip was nearly 1.2 m. Another small asperity was estimated also near the northern edge of the fault plane. These two asperities corresponded to the two distinct wave packets observed at the stations near the source region. Furthermore, the results suggested that a discrepancy in frequency characteristics between these asperities existed, by comparing them with waveforms obtained just above the source region. We also estimated the stress drop on the fault plane by the final slip distribution, and the maximum value was about 16 MPa. This result meant that the strong ground motion excitation of this earthquake was of an average level compared to past crustal earthquakes in Japan.

The 2015 Mw7.2 Sarez Strike‐Slip Earthquake in the Pamir Interior: Response to the Underthrusting of India's Western Promontory

The Pamir orogen, Central Asia, is the result of the ongoing northward advance of the Indian continent causing shortening inside Asia. Geodetic and seismic data place the most intense deformation along the northern rim of the Pamir, but the recent 7 December 2015, Mw7.2 Sarez earthquake occurred in the Pamir's interior. We present a distributed slip model of this earthquake using coseismic geodetic data and postseismic field observations. The earthquake ruptured an ∼80 km long, subvertical, sinistral fault consisting of three right‐stepping segments from the surface to ∼30 km depth with a maximum slip of three meters in the upper 10 km of the crust. The coseismic slip model agrees well with en échelon secondary surface breaks that are partly influenced by liquefaction‐induced mass movements. These structures reveal up to 2 m of sinistral offset along the northern, low‐offset segment of modeled rupture. The 2015 event initiated close to the presumed epicenter of the 1911 Mw∼7.3 Lake Sarez earthquake, which had a similar strike‐slip mechanism. These earthquakes highlight the importance of NE trending sinistral faults in the active tectonics of the Pamir. Strike‐slip deformation accommodates shear between the rapidly northward moving eastern Pamir and the Tajik basin in the west and is part of the westward (lateral) extrusion of thickened Pamir plateau crust into the Tajik basin. The Sarez‐Karakul fault system and the two large Sarez earthquakes likely are crustal expressions of the underthrusting of the northwestern leading edge of the Indian mantle lithosphere beneath the Pamir.

Tsunamis from strike-slip earthquakes in the Wharton Basin, northeast Indian Ocean: March 2016Mw7.8 event and its relationship with the April 2012Mw 8.6 event

The Wharton Basin, off southwest Sumatra, ruptured to a large intraplate left-lateral strike-slip Mw 7.8 earthquake on 2016 March 2. The epicentre was located ∼800 km to the south of another similar-mechanism intraplate Mw 8.6 earthquake in the same basin on 2012 April 11. Small tsunamis from these strike-slip earthquakes were registered with maximum amplitudes of 0.5−1.5 cm on DARTs and 1−19 cm on tide gauges for the 2016 event, and the respective values of 0.5−6 and 6−40 cm for the 2012 event. By using both teleseismic body waves and tsunami observations of the 2016 event, we obtained optimum slip models with rupture velocity (Vr) in the range of 2.8–3.6 km s−1 belonging to both EW and NS faults. While the EW fault plane cannot be fully ruled out, we chose the best model as the NS fault plane with a Vr of 3.6 km s−1, a maximum slip of 7.7 m and source duration of 33 s. The tsunami energy period bands were 4−15 and 7−24 min for the 2016 and 2012 tsunamis, respectively, reflecting the difference in source sizes. Seismicity in the Wharton Basin is dominated by large strike-slip events including the 2012 (Mw 8.6 and 8.2) and 2016 (Mw 7.8) events, indicating that these events are possible tsunami sources in the Wharton Basin. Cumulative number and cumulative seismic-moment curves revealed that most earthquakes are of strike-slip mechanisms and the largest seismic-moment is provided by the strike-slip earthquakes in this basin.

On the relationship between structure, morphology and large coseismic slip: A case study of the Mw 8.8 Maule, Chile 2010 earthquake

Subduction megathrust earthquakes show complex rupture behaviour and large lateral variations of slip. However, the factors controlling seismic slip are still under debate. Here, we present 2-D velocity-depth tomographic models across four trench-perpendicular wide angle seismic profiles complemented with high resolution bathymetric data in the area of maximum coseismic slip of the Mw 8.8 Maule 2010 megathrust earthquake (central Chile, 34°–36°S). Results show an abrupt lateral velocity gradient in the trench-perpendicular direction (from 5.0 to 6.0 km/s) interpreted as the contact between the accretionary prism and continental framework rock whose superficial expression spatially correlates with the slope-shelf break. The accretionary prism is composed of two bodies: (1) an outer accretionary wedge (5–10 km wide) characterized by low seismic velocities of 1.8–3.0 km/s interpreted as an outer frontal prism of poorly compacted and hydrated sediment, and (2) the middle wedge (∼50 km wide) with velocities of 3.0–5.0 km/s interpreted as a middle prism composed by compacted and lithified sediment. In addition, the maximum average coseismic slip of the 2010 megathrust event is fairly coincident with the region where the accretionary prism and continental slope are widest (50–60 km wide), and the continental slope angle is low (<5°). We observe a similar relation along the rupture area of the largest instrumentally recorded Valdivia 1960 Mw 9.5 megathrust earthquake. For the case of the Maule event, published differential multibeam bathymetric data confirms that coseismic slip must have propagated up to ∼6 km landwards of the deformation front and hence practically the entire base of the middle prism. Sediment dewatering and compaction processes might explain the competent rheology of the middle prism allowing shallow earthquake rupture. In contrast, the outer frontal prism made of poorly consolidated sediment has impeded the rupture up to the deformation front as high resolution seismic reflection and multibeam bathymetric data have not showed evidence for new deformation in the trench region.

Reprint of: Rupture processes of the 2015 Mw 7.9 Gorkha earthquake and its Mw 7.3 aftershock and their implications on the seismic risk

The rupture processes of the 2015 April 25 Gorkha earthquake and its strongest aftershock occurred on May 12 in Nepal are investigated by joint inversion of seismological and geodetic data. Synthetic test shows that the sedimentary layers in the source region play an important role in the rupture process inversion. Our optimized model of the mainshock shows that the rupture has a unilateral propagation pattern. The dominant mechanism is pure thrust with maximum slip of 5.8m, the rupture scale extends ~60km along dip and ~150km along strike, and the largest static stress change is ~7.6MPa. The total seismic moment is 7.87×1020Nm, equivalent to Mw 7.9. Most seismic moment was released within 80s and the majority seismic moment was released at the first 40s. The rupture propagated in main slip asperity with a velocity of ~3.0km/s. The strong aftershock magnitude is about Mw 7.3, and the peak slip is about 5.0m, close to the peak slip of the mainshock. Moreover, the slips of the mainshock and the aftershocks are in good complementary, suggesting a triggering relationship between them. Considering the strain accumulation, the Gorkha earthquake ruptured only part of the seismic gap alone, thus still poses high earthquake risk, especially in the west side of the mainshock rupture zone.

Joint inversion of GPS, InSAR and teleseismic data sets for the rupture process of the 2015 Gorkha, Nepal, earthquake using a generalized ABIC method

Various observations are made to invert for the source model of the 2015 Gorkha earthquake. Previously published slip models involve different slip distributions and slip amplitudes. To obtain a robust model, we jointly invert for the rupture process of the Gorkha earthquake using three types of observations: Global Positioning System (GPS), Interferometric Synthetic Aperture Radar (InSAR), and teleseismic P wave data. Three constraints (i.e., spatial and temporal smoothness and minimum moment constraints) are applied to regulate the rupture process. The weight ratios between data sets and prior constraints are determined from a new developed generalized Akaike’s Bayesian Information Criterion (gABIC) weight determination method. This gABIC method can simultaneously and objectively weigh various kinds of observations and prior constraints, rather than being limited to the two types in the traditional ABIC method. The inverted slip model reveals the seismic moment of the earthquake is 9.40×1020Nm released primarily in the first 60s, equivalent to Mw 7.92. The rupture front propagates unilaterally along the strike direction and spreads in both the strike and dip directions. The slip distribution shows one large slip patch with two peaks along the strike direction with a maximum slip amplitude of approximately 7.6m and identifies large slips (> 2m) that occur in the updip section of the Main Himalayan Thrust (MHT) fault plane. Our results indicate that the released slip amplitude is larger than the accumulated slip amplitude since 1833, so the 2015 earthquake likely does not overlap with the 1833 earthquake.

Imbricated slip rate processes during slow slip transients imaged by low-frequency earthquakes

Low Frequency Earthquakes (LFEs) often occur in conjunction with transient strain episodes, or Slow Slip Events (SSEs), in subduction zones. Their focal mechanism and location consistent with shear failure on the plate interface argue for a model where LFEs are discrete dynamic ruptures in an otherwise slowly slipping interface. SSEs are mostly observed by surface geodetic instruments with limited resolution and it is likely that only the largest ones are detected. The time synchronization of LFEs and SSEs suggests that we could use the recorded LFEs to constrain the evolution of SSEs, and notably of the geodetically-undetected small ones. However, inferring slow slip rate from the temporal evolution of LFE activity is complicated by the strong temporal clustering of LFEs. Here we apply dedicated statistical tools to retrieve the temporal evolution of SSE slip rates from the time history of LFE occurrences in two subduction zones, Mexico and Cascadia, and in the deep portion of the San Andreas fault at Parkfield. We find temporal characteristics of LFEs that are similar across these three different regions. The longer term episodic slip transients present in these datasets show a slip rate decay with time after the passage of the SSE front possibly as t−1/4. They are composed of multiple short term transients with steeper slip rate decay as t−α with α between 1.4 and 2. We also find that the maximum slip rate of SSEs has a continuous distribution. Our results indicate that creeping faults host intermittent deformation at various scales resulting from the imbricated occurrence of numerous slow slip events of various amplitudes.

Coseismic deformation of the 2016 Taiwan Mw6.3 earthquake using InSAR data and source slip inversion

An earthquake of seismic moment magnitude (Mw)6.3 occurred in southern Taiwan on February 6th, 2016. In this paper, we use differential interferometric synthetic aperture radar (D-InSAR) technology and data from the Sentinel-1A(S-1A)/IW radar satellite to estimate the coseismic deformation of this event. On the basis of ascending data, InSAR analysis reveals a circle-like uplift area, 45km in diameter, 20km northwest of the epicenter, that has a maximum line of sight (LOS) displacement of 12cm. South and east of this uplift area, minor subsidence occurred, while descending data indicated uplift in the west and sink in the east, with maximum values of 8.0cm and 6.0cm, respectively. Displacements are continuously distributed across the entire deformed region, implying that the seismogenic fault did not pierce the Earth’s surface. Based on these InSAR displacements coupled with GPS observations, we inverted the distribution of source slip using an elastic half-space fault model both separately and jointly. Four kinds of inversion results consistently show a slip concentration to the northwest of the epicenter, with maximum slip in the range 0.35–0.55m confined to depths of 6–15km in the crust. The source fault is dominated by thrust with left-lateral strike slip; joint inversion using InSAR ascending and descending data, as well as GPS data, resulted in maximum slip of 0.44m, within the range determined by separate inversions. Inversion results show that this was aMw6.25 earthquake, consistent with measurements collected by the United States Geological Survey (USGS).

A study on an AC electroosmotic micropump using a square pole – Slit electrode array

The paper presents a novel AC electroosmotic micropump using a square pole – slit electrode array called the SS-ACEO-MP. The AC electroosmosis (ACEO) generates convection flows when AC voltage is applied to a liquid such as water with fixed electrodes. The ACEO flow is stable without electrolysis due to the low AC voltage; however, to realize a micropump for wide applications, a special mechanism for a unidirectional flow is required. For that purpose, conventional devices utilize asymmetric electrodes, induced-charge electroosmosis, and traveling wave voltage. For practical applications, high slip velocity due to ACEO is required. The proposed pump consists of a square pole – slit electrode array, and efficiently generates a total flow by the slip velocity mainly on the slit electrodes. The proposed pump features a simple pillar-shaped structure without moving parts, efficient flow generation, and easy improvements of the pressure and the flow rate due to the arrayed structure. First, 3D FEM (finite element method) simulation of the SS-ACEO-MPs was performed and the characteristics were clarified. The size parameters that maximize the effective slip velocity under no load were clarified. Second, the SS-ACEO-MPs were fabricated by a MEMS (micro electro mechanical systems) fabrication process that included electroforming. Third, experiments on the SS-ACEO-MPs were performed. The characteristics of the SS-ACEO-MPs were clarified. Finally, at the applied voltage of 26Vpp, the maximum effective slip velocity of 1.6mm/s was realized with a unit size of 0.2×0.2×0.05mm3.

Simulation and experiment on transient temperature field of a magnetorheological clutch for vehicle application

The unpredictable power fluctuation due to severe heating has been demonstrated to be a critical bottleneck technique restricting the application of magnetorheological (MR) clutches in vehicle industry. The aim of this study is to introduce a low-cost transient simulation approach for evaluating the heat build-up and dissipation of a liquid-cooled MR vehicle clutch. This paper firstly performs a detailed description of the developed MR clutch in terms of operation principle, material selection and configuration. Subsequently, transient temperature simulations are carried out under various conditions to reveal the distribution, variation and impact factors of the transient temperature field. Following these, an experimental setup is established for heating tests of the clutch prototype. Experimental results concerning the temperature variation of magnetorheological fluids and the maximum allowable transient slip power of the clutch prototype are presented, which in return verify the correctness and feasibility of the simulation.

Control scheme for DFIG converter system based on DC‐transmission

This study proposes a novel control scheme for doubly-fed induction generator (DFIG) in DC-grid where its stator and rotor are connected to DC-bus via insulated-gate bipolar transistor (IGBT)-based converters, namely rotor side converter and stator side converter (SSC). Maximum slip frequency strategy is proposed to determine stator frequency and improve stator voltage at low-rotor speed, which could lower the design difficulty of SSC. Stator voltage decreases with stator frequency at low-rotor speed, and keeps its rated value at normal rotor speed. The control strategy of constant stator voltage and constant rotor exciting current is adopted to make DFIG operate at normal and low-rotor speed, respectively, and low-speed wind energy is utilised accordingly. Furthermore hysteresis control strategy is adopted to avoid frequent switching in the strategy switching process. Experiment results validate the feasibility and effectiveness of the proposed control scheme.

Insights into the causal relationship between slow slip and tectonic tremor in Guerrero, Mexico

AbstractSimilar to other subduction zones, tectonic tremors (TTs) and slow‐slip events (SSEs) take place in the deep segment of the plate interface in Guerrero, Mexico. However, their spatial correlation in this region is not as clear as the episodic tremor and slip observed in Cascadia and Japan. In this study we provide insights into the causal relationship between TTs and SSEs in Guerrero by analyzing the evolution of the deformation fields induced by the long‐term 2006 SSE together with new locations of TTs and low‐frequency earthquakes (LFEs). Unlike previous studies we find that the SSE slip rate modulates the TT and LFE activity in the whole tremor region. This means that the causal relationship between the SSE and the TT activity directly depends on the stressing rate history of the tremor asperities that is modulated by the surrounding slip rate. We estimated that the frictional strength of the asperities producing tremor downdip in the sweet spot is around 3.2 kPa, which is ~2.3 times smaller than the corresponding value updip in the transient zone, partly explaining the overwhelming tremor activity of the sweet spot despite that the slow slip there is smaller. Based on the LFE occurrence‐rate history during the interlong‐term SSE period, we determined that the short‐term SSEs in Guerrero take place further downdip (about 35 km) than previously estimated, with maximum slip of about 8 mm in the sweet spot. This new model features a continuum of slow slip extending across the entire tremor region of Guerrero.

UTILIZATION OF WASTE PLASTIC BOTTLES AS FINE AGGREGATE IN CONCRETE

As human communities grow larger and larger, the problem of waste management becomes one of urgent need that should be solved. Recycling and reusing of the waste materials is an efficient measure in management of the waste materials, which in addition to preventing the pollution, it conserves natural resources. Plastic bottles made of polyethylene terephthalate (PET), constitutes a major fraction of household wastes. They are classified as non- biodegradable waste materials which are harmful for public health. So making use of PET in concrete production can be useful method to get rid of plastics solid waste damage on environment. In this research, effect of using waste PET that was converted to granules in concrete has been studied experimentally. Different proportion of sand ranging from 1% to 8%, were replaced by granulated plastic. The resulting concrete was compared with normal concrete without any addition of granulated plastic. Then the specimen were tested at 7 and 28 days after curing, and some engineering properties of the mixtures including slump test, fresh and dry density, compressive, and slip strength have been investigated. Analyzing experimental results of this work indicated that optimum dosage of waste bottles replacement is 2% as fine aggregate- substitution aggregate to get maximum compressive strength and slip strength.

Large and primarily updip afterslip following the 2012 Mw 7.6 Nicoya, Costa Rica, earthquake

AbstractWe present detailed surface measurements of the first 3.5 years of postseismic deformation following the 5 September 2012 moment magnitude (Mw) 7.6 Nicoya, Costa Rica, earthquake. The dominant signal in the first 2.5 years is uniform horizontal trenchward motion totaling 7–26 cm across 40 stations. Trenchward velocity is strongly diminished by mid‐2014 and appears by 2016 to have begun reversing. We invert the first 2.5 years to determine the corresponding afterslip on a detailed 3‐D interface. Results show significant afterslip both updip and downdip of the main coseismic rupture zone, with as much as 1.7 m of offset in two patches at 15–20 km depth and immediately updip of the maximum coseismic slip. This updip slip represents an important mechanism to address unrelieved interseismic locking, although sufficient strain energy remains to generate up to a Mw 7.1 event near the coastline. The afterslip patches are anticorrelated with strongly clustered aftershocks at the same depth, which is indicative of varying frictional behavior along strike. An additional patch of slip is colocated with reoccurring slow‐slip events beneath the Gulf of Nicoya. The magnitude of the observed slip, however, cannot be sufficiently explained by the known slow‐slip events. Ongoing measurements will be crucial to understanding the relocking process in Nicoya.

Characterization of Aseismic Fault-Slip in a Deep Hard Rock Mine Through Numerical Modelling: Case Study

Seismic moment is a predominantly utilized parameter for assessing fault-slip potential when the numerical modelling of fault-slip is carried out. However, relying on seismic moment as an indicator for fault-slip might lead to incorrect conclusions, as fault-slip can be inherently seismic or aseismic. The present study examines the behaviour of a fault in Copper Cliff Mine, Canada, with a 3D numerical model encompassing major geological structures in the area of interest. Three types of numerical analyses are conducted, namely elastic and elasto-plastic analyses in static conditions and elasto-plastic analysis in dynamic conditions. The static analyses show that the fault most likely had undergone shear failure at the pre-mining stage. It is then demonstrated that mining activities induce further shear movements along the fault plane as well as within the fault material, as the fault is composed of thick, severely fractured materials. Notwithstanding the results, no large seismic events with Mw > 0.1 were recorded within the fault from microseismic-monitoring systems between 2006 and 2014, implying that the shear movements are aseismic and static. Furthermore, microseismic database analysis using 350,000 events that took place between 2004 and 2014 indicates that the fault is not seismically active. It is found from the dynamic analysis that the maximum slip rate during fault-slip is not more than 0.3 m/s, even when the fault-slip is simulated with an instantaneous stress drop. This result substantiates the assumption that the fault is not seismically active and shear movements are dominantly aseismic. It is therefore suggested that other factors such as stress re-distribution induced by the aseismic slip be considered in order to assess damage that could be caused by the fault movements. The present study sheds light on the importance of distinguishing aseismic from seismic fault-slip for optimizing support systems in underground mines.

A study on the seismogenic structure of the 2016 Zaduo, Qinghai Ms6.2 earthquake using InSAR technology

On October 17th, 2016, a Ms6.2 earthquake occurred in Zaduo County of Qinghai Province, China. The aim of this study is to use synthetic aperture radar (SAR) technology aboard the Sentinel-1A satellite to obtain high-resolution co-seismic surface displacement data and then to confirm the geometric parameters of the fault and slip distribution model. To this end, linear and non-linear inversion algorithms based on an elastic half-space dislocation model were used. The results showed that a distributed slip model can explain the surface deformation field measured by InSAR very well. The surface deformation field caused by the earthquake was an oval-shaped region of subsidence with a maximum displacement of 5 cm along the line of sight of the radar waves. This earthquake was mainly the result of a normal-slip fault process with 72°N strike and 65° dip. The slip was mainly concentrated at depths of 9–15 km. The maximum slip was 0.17 m, located at a depth of 12 km. The moment magnitude given by inversion was Mw5.9. This was basically in agreement with the moment magnitudes and surface magnitudes measured by USGS and CENC.

Anomalously large complete stress drop during the 2016 Mw 5.2 Borrego Springs earthquake inferred by waveform modeling and near‐source aftershock deficit

AbstractThe 2016 Mw 5.2 Borrego Springs earthquake occurred in the trifurcation area of the San Jacinto Fault Zone and generated more than 23,000 aftershocks. We analyze source properties of this earthquake along with 12,487 precisely located aftershock hypocenters to obtain an unusually detailed view of the rupture process and energy budget for this moderate earthquake. Source time functions are obtained using an empirical Green's function approach and are inverted for a slip distribution on the fault plane. The rupture propagated unilaterally to the northwest over a distance of 1.8 km, resulting in clear directivity signals. Two asperities are identified and the maximum slip is 2.54 m, resulting in a static stress drop of 78.2 MPa. Over 97% of the aftershocks occur more than 1 rupture length from the slip area. We conclude that the Borrego Springs earthquake had a complete stress drop and estimate the seismic efficiency to be 15–26%.