Maximum Slip Research Articles

On the early-age bond-slip behavior of an eccentric bar embedded in a grouted sleeve

Grouted-sleeve connections are widely used to connect prefabricated concrete members. The bond stress-slip behavior is an essential issue to be considered when assessing the performance of a grouted-sleeve connection loaded in tension. This paper presents an experimental investigation regarding the local and global bond stress-slip behavior of grouted-sleeve connections. Three parameters were investigated: the embedment length, construction eccentricity, and loading time after grouting, respectively. The specimens were subjected to a monotonic tensile load, and the slip between the bar and the grouted-sleeve was measured during the test. Moreover, to evaluate the confinement effect, the circumferential strain at the surface of the grouted-sleeve was measured. The results reveal that the maximum local bond stress increases with the age of the grout, whereas it decreases as the construction eccentricity of the bar increases. Moreover, the influence of the construction eccentricity is mitigated by a longer bonded length. The load-slip relationship is approximately linear for the specimen with an embedment length-to-bar diameter ratio equal to ten, loaded at the age of seven days. Based on the experimental results, an analytical model, including the local and global bond stress-slip relationship, is proposed to evaluate the maximum slip and to describe the strain distribution in the long specimens (lb/d = 6, 10). The agreement among the experimental and calculated bond stress, the maximum slip and strain distribution at the surface of the sleeve demonstrates the validity of the proposed model.

The seismic and lateral resistance of column-and-tie wooden buildings based on mortise-tenon joint

ABSTRACTThe seismic and lateral resistance of column-and-tie wooden buildings was studied in this research. A simple mortise and tenon side joint model and an overall framework model were established. Earthquake and horizontal axial force were simulated by two independent jacks. The results demonstrated that mortise and tenon joints had deformation and stiffness degradation, the global slip of the framework and slip of the column footing increased with the increase of the load. The maximum global slip was 100 mm, and the maximum slip of column footing exceeded 30 mm. The global slip was small, suggesting good seismic and lateral resistance of column-and-tie buildings. The experimental results can provide some theoretical support for the reinforcement and development of column-and-tie wooden buildings.

Experimental shear testing of timber-masonry dry connections for the seismic retrofit of unreinforced masonry shear walls

Abstract The mechanical coupling of timber products to the masonry walls of unreinforced masonry (URM) buildings is generating considerable interest in terms of seismic vulnerability mitigation. An extensive experimental investigation on timber panel to masonry wall connections realised with screw anchor fasteners is presented. A total of 64 shear tests under monotonic, cyclic and semi-cyclic loading conditions were performed on site in a historic URM building. The examined parameters were: masonry type, timber panel product and material, load-to-grain direction, fastener geometry and steel grade. The outcomes of the campaign are then reported and discussed focusing on the strength and stiffness properties and on the dissipation capacity and residual strength of the connection under cyclic load. Moreover, a log-normal distribution fitting is proposed for the maximum load and slip modulus measurements of all the cyclic test configurations analysed. Finally, the principal experimental observations are listed along with recommendations for future work or use in practice.

Rupture of the Indian Slab in the 2011 Mw 6.9 Sikkim Himalaya Earthquake and Its Tectonic Implications

AbstractUnlike the other Himalayan plate boundary segments, the eastern Nepal to Bhutan Himalayan region is not known to have generated prominent shallow thrust faulting earthquakes, typical of the ongoing convergence. This region features strike‐slip earthquakes over the depth ranges of 40–120 km, indicating intraslab deformation. Here we present for the first time a slip distribution model for the largest recorded intraslab strike‐slip earthquake in this region, the Mw 6.9 Sikkim event that occurred on 18 September 2011. Relying on kinematic source process modeling, our results indicate a NE‐SW trending, steeply dipping sinistral source zone within the underthrusting Indian slab. The rupture propagated radially, with a low rupture velocity of 1.7 km/s, breaking a large asperity of 20 × 20 km2 with a maximum slip of 1.6 m. The rupture nucleated at a depth of 45 km and reached upper mantle depths. The computed coseismic stress drop value is 13.6 MPa. We suggest that most of the aftershocks occurred on the conjugate plane, possibly due to stress triggering. Stress inversion of focal mechanisms indicates a transpressive stress regime throughout the crust and pure strike‐slip regime in the upper mantle. We observed a unimodal distribution of earthquakes beneath the Higher Himalaya. This indicates a strong, brittle Indian slab and unravels a scenario of an eventual breakup of the lithosphere; the key trigger might be variation in the convergence rates along the Himalayan arc.

Source Parameter Estimation of the 2009 Ms6.0 Yao’an Earthquake, Southern China, Using InSAR Observations

On 9 July 2009, an Ms6.0 earthquake occurred in mountainous area of Yao’an in Yunnan province of Southern China. Although the magnitude of the earthquake was moderate, it attracted the attention of many Earth scientists because of its threat to the safety of the population and its harm to the local economy. However, the source parameters remain poorly understood due to the sparse distribution of seismic and GNSS (Global Navigation Satellite System) stations in this mountainous region. Therefore, in this study, the two L-band ALOS (Advanced Land Observing Satellite-1) PALSAR (Phased Array type L-band Synthetic Aperture Radar) images from an ascending track is used to investigate the coseismic deformation field, and further determine the location, fault geometry and slip distribution of the earthquake. The results show that the Yao’an earthquake was a strike-slip event with a down-dip slip component. The slip mainly occurred at depths of 3–8 km, with a maximum slip of approximately 70 cm at a depth of 6 km, which is shallower than the reported focal depth of ~10 km. An analysis of the seismic activity and tectonics of the Yao’an area reveals that the 9 July 2009 Yao’an earthquake was the result of regional stress accumulation, which eventually led to the rupture of the northwestern most part of the Maweijing fault.

Kinematics of the 2012 Ahar–Varzaghan complex earthquake doublet (Mw6.5 and Mw6.3)

On 2012 August 11, an earthquake doublet (Mw6.5 and Mw6.3), separated in time by 11 min, occur in the northwest of Iran. The hypocentres of these earthquakes are close (∼6 km) and located near the cities of Ahar and Varzaghan. The rupture process of both main shocks is retrieved by inverting the near-field strong motions data and using the elliptical subfault approximation method. Our calculations show that the two earthquakes are occurring on two distinct fault planes: the first main shock (M1) has nucleated at a depth of ∼8.5 km, and is located ∼4 km east of the eastern termination of the E-W trending surface rupture. The slip reaches the ground surface west of the hypocentre on an E-W striking fault (N88°E) that dips almost vertically (80°S). This earthquake exhibits a right-lateral strike-slip mechanism. The entire slip is imaged on a single patch that ruptures with an average speed of 2.4 km s−1. The rupture duration is ∼5.6 s and the earthquake releases a seismic moment of ∼8.41E + 18 N·m. The slip reaches the surface with a right-lateral dislocation value of ∼1 m, which is consistent with the observed surface rupture. About 11 min later, the second main shock (M2) nucleates ∼5 km to the west and 4 km to the north with respect to the hypocentre of the M1, and at a depth of ∼16.5 km. The M2 rupture evolves toward shallower depths and to the west on an ENE-WSW oriented fault plane (strike ∼256°) with a dip of ∼60° northward. The slip is essentially distributed on two distinct patches with strike-slip and reverse mechanisms, respectively. The first patch has a pure right-lateral strike-slip mechanism, and ruptures at a relatively fast speed of over 2.8 km s−1, and last for about 2.6 s until it reaches the second patch. The latter has a reverse mechanism (rake∼112°) and extends the rupture toward shallow depths, and to the west at a speed of ∼2.5 km s−1, and its rupture lasts for ∼2.5 s. The top of the slip distribution of M2 stops at a depth of ∼8 km. We observe that aftershocks surround the M1 and most of the M2 slip models. They are not distributed in the region of high slip (∼3.1 m) of M1. We show that the rupture of M2 is controlled by the static Coulomb stress changes caused by M1, with the maximum slip of M2 located in the positive Coulomb stress caused by M1. The M2 rupture stops where it reaches the area of high negative Coulomb stress change (over −10 bars). The cumulative Coulomb stress fields of both main shocks show a transfer of positive static Coulomb stress change of >0.1 bars on the eastern segment of the North Tabriz Fault. This segment did not rupture since the 1721 M∼7.6–7.7 event that has destroyed the city of Tabriz, and that currently hosts 2 million people. The occurrence of this earthquake doublet with different mechanisms reveals the slip partitioning of the oblique convergence regime of NW Iran on the Ahar–Varzaghan complex fault system.

Co- and post-seismic Deformation Mechanisms of the MW 7.3 Iran Earthquake (2017) Revealed by Sentinel-1 InSAR Observations

The extraction of high-accuracy co- and post-seismic deformation fields and inversions of seismic slip distributions is significant in the comprehension of seismogenic mechanisms. On 12 November 2017, a MW 7.3 earthquake occurred on the border between Iran and Iraq. To construct the co-seismic deformation field, Sentinel-1A synthetic aperture radar (SAR) images from three tracks were used. Based on a prior knowledge, least-squares iterative approximation was employed to construct the three-dimensional (3D) co-seismic deformation field. to derive a time series of 2D post-seismic deformation, the multidimensional small baseline subset (MSBAS) technique was use. Co-seismic deformation fields were asymmetric; the maximum relative displacement was nearly 90cm in the radar line-of-sight between two centers of co-seismic deformation. The 3D co-seismic deformation field showed southwestward horizontal motion and continuous subsidence-to-uplift variation from northeast to southwest. The two-dimensional (2D) post-seismic deformation time series showed a gradual decaying trend and good correspondence with the aftershock distribution. The main mechanism of post-seismic deformation was an afterslip of the post-seismic faults. We used the elastic half-space model to invert co-seismic deformation fields and obtain source parameters of the slip model. The maximum and average slips were 2.5 and 0.72 m, respectively. The average slip angle was 126.38° and the moment magnitude was MW 7.34. The results of this study will contribute to research on regional tectonic activities.

Postglacial faulting near Crater Lake, Oregon, and its possible association with the Mazama caldera-forming eruption

Abstract Volcanoes of subduction-related magmatic arcs occur in a variety of crustal tectonic regimes, including where active faults indicate arc-normal extension. The Cascades arc volcano Mount Mazama overlaps on its west an ∼10-km-wide zone of ∼north-south–trending normal faults. A lidar (light detection and ranging) survey of Crater Lake National Park, reveals several previously unrecognized faults west of the caldera. Postglacial vertical separations measured from profiles across scarps range from ∼2 m to as much as 12 m. Scarp profiles commonly suggest two or more postglacial surface-rupturing events. Ignimbrite of the ca. 7.6 ka climactic eruption of Mount Mazama, during which Crater Lake caldera formed, appears to bury fault strands where they project into thick, valley-filling ignimbrite. Lack of lateral offset of linear features suggests principally normal displacement, although predominant left stepping of scarp strands implies a component of dextral slip. West-northwest–east-southeast and north-northwest–south-southeast linear topographic elements, such as low scarps or ridges, shallow troughs, and straight reaches of streams, suggest that erosion was influenced by distributed shear, consistent with GPS vectors and clockwise rotation of the Oregon forearc block. Surface rupture lengths (SRL) of faults suggest earthquakes of (moment magnitude) Mw6.5 from empirical scaling relationships. If several faults slipped in one event, a combined SRL of 44 km suggests an earthquake of Mw7.0. Postglacial scarps as high as 12 m imply maximum vertical slip rates of 1.5 mm/yr for the zone west of Crater Lake, considerably higher than the ∼0.3 mm/yr long-term rate for the nearby West Klamath Lake fault zone. An unanswered question is the timing of surface-rupturing earthquakes relative to the Mazama climactic eruption. The eruption may have been preceded by a large earthquake. Alternatively, large surface-rupturing earthquakes may have occurred during the eruption, a result of decrease in east-west compressive stress during ejection of ∼50 km3 of magma and concurrent caldera collapse.

Coseismic and Postseismic Deformation of the 2016 Mw 6.6 Aketao Earthquake from InSAR Observations and Modelling

On November 25, 2016, the Mw 6.6 Aketao earthquake occurred in Xinjiang, western China. We used the combination of ascending Sentinel-1A, descending Sentinel-1B and ascending ALOS-2 PALSAR data to measure the coseismic deformation. The line-of-sight (LOS) coseismic deformation implies that the earthquake was dominated by right-lateral strike-slip. Ignoring the fault-perpendicular deformation, the fault-parallel and up–down deformation was extracted based on the combination of Sentinel-1A and 1B observations. Results show that the maximum fault-parallel deformation is ~ 13.7 cm at the north wall and the minimum is ~ −16.5 cm at the south wall of the Muji fault. Then, coseismic slip distribution was derived using the steepest descent method (SDM) based on a single-segment fault model using the three InSAR LOS observations as constraints. The slip distribution reveals two slip centers. The maximum slip of the eastern center is 0.5 m at a depth of 8.8 km, where the rake angle is ~ 181.2°. The maximum slip of the western center is 0.6 m at a depth of 10.8 km, where the rake angle is ~ 181.1°. The derived seismic moment obtained equals the Mw 6.6 earthquake. In this study, postseismic deformation time series in 1.5 years after the earthquake were retrieved from 26 multi-temporal Sentinel-1 descending scenes. The postseismic LOS deformation at the north and south walls of Muji fault both increases with time but in opposite directions. The cumulative deformation is 60–80 mm at the north wall, and –30 to −20 mm at the south wall. The postseismic deformation shows similar patterns with the coseismic deformation, and has the same mechanism. There is no obvious lock at the unbroken gap.

New insights into the 2010 Yushu Mw6.9 mainshock and Mw5.8 aftershock, China, from InSAR observations and inversion

The Mw6.9 Yushu earthquake occurred on 14 April 2010, in Qinghai, China; the largest aftershock, a Mw5.8 event, occurred west of the mainshock on 29 May 2010 (˜40 days later). The aftershock had a different focal mechanism from the mainshock. Furthermore, seismicity after 29 May showed different spatial characteristics in terms of focal depth and distribution direction. To better understand the faulting and the relationship between these two events, we derived the whole displacement field caused by the Yushu mainshock and the Mw5.8 aftershock based on multi-perspective Interferometric Synthetic Aperture Radar (InSAR) data. We then conducted a robust inversion of the slip distribution jointly constrained by InSAR and GPS data. The results indicate that the Mw5.8 aftershock produced a separated deformation field with significant displacement changes of up to ˜4–6 cm, which indicates another intersecting ruptured fault at the west end of the Yushu fault. The slip distribution shows a 75-km NW rupture with a maximum slip of ˜2.1 m at a depth of ˜0–10 km on the main Yushu fault, and a 20 km NE rupture with peak slip of ˜0.4 m at a depth of ˜5–15 km on a vertical hidden fault. Both events showed a dominant left-lateral component. The total rupture length associated with the 2010 Yushu earthquake sequence reached ˜95 km. By calculating Coulomb stress changes, we confirmed that the mainshock triggered the Mw5.8 aftershock. Our results imply that the increased stress at the western end of the Yushu fault caused by the mainshock rupture may have played an important role in transferring the rupture plane from the Yushu fault to the NE hidden fault.

Anisotropic interfacial properties between monolayered black phosphorus and water

Black phosphorus (BP) has become a novel focus of the 2D material due to its natural direct band gap and high carrier mobility, but researchers seldom refer to the water-BP interfacial properties while the natural rippled surface of the BP raises great hope to develop the controllable fluid transmission devices. In this paper, the interfacial slip and friction between monolayered BP and water are first investigated using classical molecular dynamics simulations based on the BP sheet-water Couette model. The results show that the rippled structure of the BP surface leads to the anisotropic boundary slip and interfacial friction between water and BP sheets. The maximum boundary slip and the minimum interfacial friction are obtained for the water flow direction parallel to the ripple direction of BP monolayer. With increasing the intersection angle between water flow direction and BP ripple direction, the boundary slip decreases and the interfacial friction increases continuously. The mechanism of the anisotropic interfacial properties is clarified from the configuration of the water molecules adjacent to the BP surfaces. This finding will generate excitement in designing the BP-based fluid transmission device.

Rupture History of the 13th November 2017 Mw 7.3 Iran‐Iraq Border Region Earthquake Based on Teleseismic Data

We have examined the temporal and spatial slip distribution of the 2017 Mw 7.3 Iran‐Iraq border region earthquake, utilizing 49 broadband teleseismic P‐wave records. Based on the nonnegative least square method and multi‐time window, a finite fault model was used to parameterize the rupture process. According to the L‐curve, the optimal inversion result was detected. The inversion results showed that the earthquake was a shallow‐dip thrusting event. Rupture duration was 20 s, and the total seismic moment was 0.9 × 1020 N·m. There was only one asperity in the fault plane, which indicated the rupture process was simple. The slip was mainly distributed around the initial rupture point, dominated by thrust motion with a small amount of right‐lateral strike slip, and the maximum slip was 5.2 m, located on a subfault of the initial rupture. The entire rupture lasted 20 s, and 75% of the energy was released in the first 10 s. The rupture area was 825 km2, and the estimated static stress drop was 6.1 MPa.

Theoretical Investigation of the Sliding Instability and Caving Depth of Coal Wall Workface Based on the Bishop Strip Method

As mining height increases, the influence of coal wall caving on safety production becomes stronger. There is no systematic and effective method to analyse the risk of coal wall caving and its slip caving depth. First, this paper established the Bishop mechanical model of sliding instability of coal wall, and then it deduced the general equation of a safety factor for every slip surface, which can be used to judge the stability of the coal body on the slip surface. Moreover, taking the 8102 workface in the Wulonghu Mine, China, as an example, this paper evaluated the calculation method of slip surface safety factor in detail and obtained the critical slip surface position and the maximum slip depth of a coal wall. Overall, the results showed that the maximum slip depth based on the Bishop strip method is more consistent with the measured data compared with other methods and thus has strong significance and practical engineering value for selecting the most suitable method and its parameters of regulating coal wall caving.

Series Arc Detection and Complex Load Recognition Based on Principal Component Analysis and Support Vector Machine

The increasing household loads make series arc faults more complex, which are difficult to be detected by traditional circuit breakers and lead to the frequent occurrence of residential fire accidents. In this paper, a comprehensive approach of complex load recognition and series arc detection is proposed on the basis of principal component analysis and support vector machine (PCA-SVM) combination model. Several typical loads were selected and analyzed, especially nonlinear and complex loads like power electronics load and multi-state load. Three time-domain parameters, maximum slip difference (MSD), zero current period (ZCP) and maximum Euclidean distance (MED), and nine frequency-domain harmonics information are collected to complex waveforms. To decrease the computation cost and further to enhance the response velocity, all the time-domain and frequency-domain information were blended and dimensionally reduced to three parameters by principal component analysis (PCA). Prior to the series arc detection, load recognition is trained and completed with the artificial intelligence (AI) algorithm. At last, the comprehensive model of load recognition and series arc detection is achieved based on a support vector machine (SVM). The accuracy of load recognition and series arc detection reaches 99.1% and 99.3%, respectively, demonstrating the excellent performances of the intelligent approach to diagnose the series arcing activities in modern household applications.

The 2018 <i>M</i><sub>S</sub> 5.9 Mojiang Earthquake: Source model and intensity based on near-field seismic recordings

On September 8, 2018, an MS 5.9 earthquake struck Mojiang, a county in Yunnan Province, China. We collect near-field seismic recordings (epicentral distances less than 200 km) to relocate the mainshock and the aftershocks within the first 60 hours to determine the focal mechanism solutions of the mainshock and some of the aftershocks and to invert for the finite-fault model of the mainshock. The focal mechanism solution of the mainshock and the relocation results of the aftershocks constrain the mainshock on a nearly vertical fault plane striking northeast and dipping to the southeast. The inversion of the finite-fault model reveals only a single slip asperity on the fault plane. The major slip is distributed above the initiation point, ~14 km wide along the down-dip direction and ~14 km long along the strike direction, with a maximal slip of ~22 cm at a depth of ~6 km. The focal mechanism solutions of the aftershocks show that most of the aftershocks are of the strike-slip type, a number of them are of the normal-slip type, and only a few of them are of the thrust-slip type. On average, strike-slip is dominant on the fault plane of the mainshock, as the focal mechanism solution of the mainshock suggests, but when examined in detail, slight thrust-slip appears on the southwest of the fault plane while an obvious part of normal-slip appears on the northeast, which is consistent with what the focal mechanism solutions of the aftershocks display. The multiple types of aftershock focal mechanism solutions and the slip details of the mainshock both suggest a complex tectonic setting, stress setting, or both. The intensity contours predicted exhibit a longer axis trending from northeast to southwest and a maximal intensity of Ⅷ around the epicenter and in the northwest.

Dynamic Rupture Simulation Reproduces Spontaneous Multifault Rupture and Arrest During the 2016Mw7.9 Kaikoura Earthquake

AbstractThe 2016 Kaikoura (New Zealand) earthquake is characterized as one of the most complex multifault rupture events ever observed. We perform dynamic rupture simulations to evaluate to what extent relatively simple forward models accounting for realistic fault geometry can explain the characteristics of coseismic observations. Without fine parameter tuning, our model reproduces many observed features including the multifault rupture, overall slip distribution, and the locations of the maximum slip and rupture arrest. In particular, our model shows spontaneous arrest of dynamic rupture at the both ends of the ruptured fault system due to smaller prestress levels expected from a regional tectonic stress field. Both the simulated and the observationally inferred source time functions show similar double peaks with a larger second peak. The results illuminate the importance of the 3‐D fault geometry in understanding the dynamics of complex multifault rupture.

Analytical modelling of force transmission in axially loaded RC columns with indirectly loaded jackets

Concrete and steel jacketing are common strengthening techniques for reinforced concrete (RC) columns subjected to axial loads. In the most of cases the external jacket is made leaving gaps between the strengthening layer and the slabs, avoiding to carry directly a portion of the load. In this way, the external jacket induces a confinement pressure on the inner column, and its beneficial effect is due to the increase of strength and ductility. However, shear stresses develop on the interface between the column and consequently, the external jacket can be considered indirectly loaded. It sustains a portion of the axial load, which depends by the value of the axial shortening, relative slippage between core and jacket and therefore by geometrical and mechanical features of the system. The evaluation of this effect is quite complex, since it depends from several parameters. This paper presents an analytical model able to predict the distribution of relative slips and shear stresses at interface in axially loaded RC columns reinforced with indirectly loaded jackets. Closed form expressions of maximum slip and stress distribution are obtained for linear elastic materials and formulation is extended to RC members via a step-by-step procedure allowing also to obtain the overall load-shortening curve. Results show the dependence of the compressive response from the interface’s stiffness. The analytical solution is verified with results derived by non-linear finite element analyses, showing good agreement for different key parameters. Finally, comparisons with experimental data available in the literature are performed, proving the reliability of the model.

Dynamic characteristic study of composite box beam with corrugated webs considering interface slip and shear deformation

In order to study the effect of interface slip and shear deformation on the natural vibration of composite box girders with corrugated webs (CBBCW), based on the Hamilton principle, the effects of the slip, shear deformation and moment of inertia of CBBCW have been investigated. Further, the flexural vibration differential equations and natural boundary conditions of the CBBCW have been deduced. The formula for the flexural natural vibration frequency of CBBCW has been developed. The influencing rule of the interface slip stiffness and web shear deformation on the flexural natural vibration frequency of the CBBCW has been analyzed. The results of this study show that the analytical results are in good agreement with the results of the ANSYS finite element calculation, and some significant conclusions can be applied to the engineering design. The interface slip stiffness has some effect on the flexural natural vibration frequency of the CBBCW, and the maximum interface slip effect is up to 13.7%. The shear deformation has a significant effect on the natural vibration properties of the CBBCW, and the shear deformation effect increases significantly with the increase of the order of flexural natural vibration frequency. The formula has been developed further as compared with the earlier developed calculation theory for the flexural natural vibration of CBBCW. It can also provide a reference for future study of dynamic characteristics of CBBCW.

Geomorphic evidence for the geometry and slip rate of a young, low-angle thrust fault: Implications for hazard assessment and fault interaction in complex tectonic environments

We present surface evidence and displacement rates for a young, active, low-angle (∼20°) reverse thrust fault in close proximity to major population centers in southern California (USA), the Southern San Cayetano fault (SSCF). Active faulting along the northern flank of the Santa Clara River Valley displaces young landforms, such as late Quaternary river terraces and alluvial fans. Geomorphic strain markers are examined using field mapping, high-resolution lidar topographic data, 10Be surface exposure dating, and subsurface well data to provide evidence for a young, active SSCF along the northern flank of the Santa Clara River Valley. Displacement rates for the SSCF are calculated over 103–104 yr timescales with maximum slip rates for the central SSCF of 1.9+1.0−0.5 mm yr−1 between ∼19–7 ka and minimum slip rates of 1.3+0.5−0.3 mm yr−1 since ∼7 ka. Uplift rates for the central SSCF have not varied significantly over the last ∼58 ka, with a maximum value of 1.7+0.9−0.6 mm yr−1 for the interval ∼58–19 ka, and a minimum value of 1.2±0.3 mm yr−1 since ∼7 ka. The SSCF is interpreted as a young, active structure with onset of activity at some time after ∼58 ka. The geometry for the SSCF presented here, with a ∼20° north dip in the subsurface, is the first interpretation of the SSCF based on geological field data. Our new interpretation is significantly different from the previously proposed model-derived geometry, which dips more steeply at 45–60° and intersects the surface in the middle of the Santa Clara River Valley. We suggest that the SSCF may rupture in tandem with the main San Cayetano fault. Additionally, the SSCF could potentially act as a rupture pathway between the Ventura and San Cayetano faults in large-magnitude, multi-fault earthquakes in southern California. However, given structural complexities, including significant changes in dip and varying Holocene displacement rates along strike, further work is required to examine the possible mechanism, likelihood, and frequency of potential through-going ruptures between the Ventura and San Cayetano faults. Confirmation of the SSCF in a previously well-studied area, such as southern California, demonstrates that identification of young faults is critical for accurate seismic hazard assessment. We suggest that many young, active faults remain undetected in other structurally complex and tectonically active regions globally, and that significant seismic hazards can be overlooked.

The 2017 Mw 7.3 Sarpol Zahāb Earthquake, Iran: A compact blind shallow-dipping thrust event in the mountain front fault basement

The 12 November 2017 Mw 7.3 Sarpol Zahāb earthquake is one of the largest events to have occurred in the north-western Zagros fold-and-thrust belt during the instrumental period. We use teleseismic and synthetic aperture radar data to study the earthquake source parameters, rupture process and active tectonic characteristics of the event. We find that both data sets individually produce remarkably similar slip distribution, indicative of buried faulting that is consistent with the lack of significant surface rupture. Through the joint inversion of satellite radar and teleseismic data, we find that the rupture propagated rapidly (~3.2 km/s) and asymmetrically along strike to the south, but relatively slowly (~1.5 km/s) in the updip direction, and formed a single large-slip asperity with a peak slip value close to 5 m. Given the regional tectonic context of the distribution of known faults and lithologies, we suggest that the maximum slip is either located in the lowest sedimentary cover or the uppermost basement of the Mountain Front Fault.