Low Slip Rates Research Articles

A systems-based approach to parameterise seismic hazard in regions with little historical or instrumental seismicity: active fault and seismogenic source databases for southern Malawi

Abstract. Seismic hazard is commonly characterised using instrumental seismic records. However, these records are short relative to earthquake repeat times, and extrapolating to estimate seismic hazard can misrepresent the probable location, magnitude, and frequency of future large earthquakes. Although paleoseismology can address this challenge, this approach requires certain geomorphic setting, is resource intensive, and can carry large inherent uncertainties. Here, we outline how fault slip rates and recurrence intervals can be estimated by combining fault geometry, earthquake-scaling relationships, geodetically derived regional strain rates, and geological constraints of regional strain distribution. We apply this approach to southern Malawi, near the southern end of the East African Rift, and where, although no on-fault slip rate measurements exist, there are constraints on strain partitioning between border and intra-basin faults. This has led to the development of the South Malawi Active Fault Database (SMAFD), a geographical database of 23 active fault traces, and the South Malawi Seismogenic Source Database (SMSSD), in which we apply our systems-based approach to estimate earthquake magnitudes and recurrence intervals for the faults compiled in the SMAFD. We estimate earthquake magnitudes of MW 5.4–7.2 for individual fault sections in the SMSSD and MW 5.6–7.8 for whole-fault ruptures. However, low fault slip rates (intermediate estimates ∼ 0.05–0.8 mm/yr) imply long recurrence intervals between events: 102–105 years for border faults and 103–106 years for intra-basin faults. Sensitivity analysis indicates that the large range of these estimates can best be reduced with improved geodetic constraints in southern Malawi. The SMAFD and SMSSD provide a framework for using geological and geodetic information to characterise seismic hazard in regions with few on-fault slip rate measurements, and they could be adapted for use elsewhere in the East African Rift and globally.

Discrete fuzzy adaptive PID control algorithm for automotive anti-lock braking system

Due to the low slip rate and poor braking performance of automobile anti-lock braking system, a discrete fuzzy adaptive PID control algorithm for automobile anti-lock braking system is designed in this paper. Based on the theory of discrete fuzzy adaptive PID control algorithm, the braking force of a vehicle is analyzed and the anti-lock control target is set. The automobile adhesion coefficient and wheel slip rate are calculated as the input and output of the PID control algorithm to complete the control of the anti-lock brake system of the network automobile. Experiments show that the sliding rate of the discrete fuzzy adaptive PID control algorithm of the designed anti-lock system is close to 20%, which proves that the design method has good braking effect.

New geodetic constraints on southern San Andreas fault-slip rates, San Gorgonio Pass, California

AbstractAssessing fault-slip rates in diffuse plate boundary systems such as the San Andreas fault in southern California is critical both to characterize seismic hazards and to understand how different fault strands work together to accommodate plate boundary motion. In places such as San Gorgonio Pass, the geometric complexity of numerous fault strands interacting in a small area adds an extra obstacle to understanding the rupture potential and behavior of each individual fault. To better understand partitioning of fault-slip rates in this region, we build a new set of elastic fault-block models that test 16 different model fault geometries for the area. These models build on previous studies by incorporating updated campaign GPS measurements from the San Bernardino Mountains and Eastern Transverse Ranges into a newly calculated GPS velocity field that has been removed of long- and short-term postseismic displacements from 12 past large-magnitude earthquakes to estimate model fault-slip rates. Using this postseismic-reduced GPS velocity field produces a best-fitting model geometry that resolves the long-standing geologic-geodetic slip-rate discrepancy in the Eastern California shear zone when off-fault deformation is taken into account, yielding a summed slip rate of 7.2 ± 2.8 mm/yr. Our models indicate that two active strands of the San Andreas system in San Gorgonio Pass are needed to produce sufficiently low geodetic dextral slip rates to match geologic observations. Lastly, results suggest that postseismic deformation may have more of a role to play in affecting the loading of faults in southern California than previously thought.

Slip-rate-dependent friction as a universal mechanism for slow slip events

A growing body of observations worldwide has documented fault slip transients that radiate little or no seismic energy. The mechanisms that govern these slow slip events (SSEs) and their wide range of depths, slip rates, durations, stress drops and recurrence intervals remain poorly known. Here we show that slow slip can be explained by a transition from rate-weakening frictional sliding at low slip rates towards rate-neutral or rate-strengthening behaviour at higher slip rates, as has been observed experimentally. We use numerical simulations to illustrate that this rate-dependent transition quantitatively explains the experimental data for natural fault rocks representative of materials in the source regions of SSEs. With a standard constant-parameter rate-and-state friction law, SSEs arise only near the threshold for slip instability. The inclusion of velocity-dependent friction parameters substantially broadens the range of conditions for slow slip occurrence, and produces a wide range of event characteristics, which include stress drop, duration and recurrence, as observed in nature. Upscaled numerical simulations that incorporate parameters consistent with laboratory measurements can reproduce geodetic observations of repeating SSEs on tectonic faults. We conclude that slip-rate-dependent friction explains the ubiquitous occurrence of SSEs in a broad range of geological environments. A transition from rate-weakening to rate-strengthening frictional behaviour with increasing slip rate could explain the observed diversity of slow slip events on faults, according to numerical simulations.

Quantitative Constraints on Faulting and Fault Slip Rates in the Northern Main Ethiopian Rift

AbstractThe Boset magmatic segment (BMS) of the northern Main Ethiopian Rift (MER) is an ideal natural laboratory to investigate the kinematics, interaction, and rates of activity within a fault network in a magma‐rich rift. In this paper we take advantage of the availability of (1) high‐resolution remote sensing data (LiDAR, ASTER); (2) absolute age chronology on offset reference surfaces; and (3) well‐exposed active normal fault arrays to place new constraints on rift kinematics and strain distribution, and to quantify the architecture and fault slip rates at different temporal scales within a magmatic segment. We found that the rift border faults strike approximately NE, while the younger faults in the rift segments strike NNE. Analyses of geometric rift parameters show that the axial active part of the rift is transtensional with an increase of the shear component northward. The fault displacement analyses and displacement:length ratios increase toward the segment tips, suggesting a significant contribution of fault growth by linkage. In contrast, magmatism is focused on the segment center and localized to a narrow zone. Estimated fault slip rates vary, with rates of up to ~0.37 mm/year in ~0.3 Ma old rift floor deposits, whereas higher rates of up to ~4.4 mm/year are observed for faults cutting through ~6 Ka lavas. The difference in slip rates indicates short‐term variability or a very active recent episode compared to long‐term low average slip rates.

Late Quaternary paleoseismology and faulting behavior of the Yilan-Yitong fault zone and implications for seismic hazards of the Tanlu fault zone, eastern China

Abstract Along the north branch of the Tanlu fault zone (TLFZ), the Yilan-Yitong fault zone (YYFZ) displaces Quaternary geomorphic features, forming a ~70-km-long fresh surface rupture. In this study, we investigated offset landforms and paleoearthquake history by excavating four trenches along the YYFZ within the Fangzheng graben combined with Quaternary dating of landforms and trench horizons. Four paleoearthquakes are identified with their timings constrained at 1730 ± 40 a BP to 770 ± 30 a BP, 28.5 ± 1.2 ka BP to 21.7 ± 0.9 ka BP, 59.4 ± 2.4 ka BP to 33.1 ± 1.1 ka BP, and before 59.4 ± 2.4 ka BP, respectively. Seismic recurrence behavior of the YYFZ follows a quasi-periodic pattern with a very long interval of 10–20 ka. Geological and geomorphic features show that the YYFZ is dominated by right-lateral strike-slip movement with a low dextral slip rate of ~0.2–0.3 mm/a in late Quaternary, in accord with present-day geodetic observations. As with the YYFZ, paleoearthquakes along the TLFZ commonly share a recurrence interval of ~10–20 ka. We suggest that active segments of the TLFZ that have been dormant for thousands of years may pose significant earthquake hazards in the future. Moreover, strain transfer from the bounding faults to those more central in the graben may be significant on the TLFZ and should be given consideration when assessing regional seismic hazards. Insight into past earthquakes and faulting behavior in a low-strain environment is crucial for earthquake-hazard analysis and often requires multidisciplinary approaches.

Robust and Low-Complexity Principal Component-Based Phase Estimation Algorithm for Probabilistically Shaped Square-QAM Systems

An optimized principal component-based phase estimation (OPCPE) algorithm is proposed for probabilistically shaped (PS) square-quadrature amplitude modulation (QAM) systems. The optimization method is based on mirroring and partially scaling the received constellation. Numerical simulation validation shows that the proposed phase recovery algorithm outperforms the well-known blind phase search (BPS) algorithm at low signal-to-noise ratio (SNR) and solves the incompatibility between principal component-based phase estimation (PCPE) and PS at high SNR. It's worth mentioning that the proposed algorithm retains the advantages of low cycle slip rate (CSR) and low computational complexity of PCPE. Furthermore, the performance of a hybrid implementation combining the proposed algorithm and BPS is also investigated. When the shaping parameter for a PS-64QAM system is 0.03, by using the proposed simple and hybrid methods, the SNR required to reach the 0.8 normalized generalized mutual information (NGMI) threshold can be reduced by about 0.74 dB and 0.98 dB, respectively, benchmarking the widely used two-stage BPS (2S-BPS) algorithm. To the best of our knowledge, this is the first time to robustly apply PCPE algorithm to PS systems, and the proposed design has stable GMI performance, strong cycle slip tolerance and low computational complexity, which makes it a suitable candidate for practical probabilistically-shaped transmissions.

Complex Rupture of an Immature Fault Zone: A Simultaneous Kinematic Model of the 2019 Ridgecrest, CA Earthquakes

AbstractThe 4 July 2019 Mw6.4 and subsequent 6 July 2019 Mw7.1 Ridgecrest sequence earthquakes (CA, USA) ruptured orthogonal fault planes in a low slip rate (1 mm/year) dextral fault zone in the area linking the Eastern California Shear Zone and Walker Lane. This region accommodates nearly one fourth of plate boundary motion and has been proposed to be an incipient transform fault system that could eventually become the main tectonic boundary, replacing the San Andreas Fault. We investigate the rupture process of these events using a novel simultaneous kinematic slip method with joint inversion of high‐rate GNSS, strong motion, GNSS static offset, and Interferometric Synthetic Aperture Radar data. We model the Coulomb stress change to evaluate how the Mw6.4 earthquake may have affected the subsequent Mw7.1 event. Our findings suggest complex interactions between several fault structures, including dynamic and static triggering, and provide important context for regional seismic source characterization and hazard models.

Sevier Fault at Red Canyon

The Sevier fault is spectacularly displayed on the north side of Utah Highway 12 at the entrance to Red Canyon, where it offsets a 500,000-year-old basaltic lava flow. The fault is one of several active, major faults that break apart the western margin of the Colorado Plateau in southwestern Utah. The Sevier fault is a “normal” fault, a type of fault that forms during extension of the earth’s crust, where one side of the fault moves down relative to the other side. In this case, the down-dropped side (the hanging wall) is west of the fault; the upthrown side (the footwall) lies to the east. The contrasting colors of rocks across the fault make the fault stand out in vivid detail. Immediately south of Red Canyon, the 5-million-year-old Rock Canyon lava flow, which erupted on the eastern slope of the Markagunt Plateau, flowed eastward and crossed the fault (which at the time juxtaposed non-resistant fan alluvium against coarse-grained volcaniclastic deposits) (Biek and others, 2015). The flow is now offset 775 to 1130 feet (235-345 m) along the main strand of the fault, yielding an anomalously low vertical slip rate of about 0.05 mm/yr (Lund and others, 2008). However, this eastern branch of the Sevier fault accounts for only part of the total displacement on the fault zone. A concealed, down-to-the-west fault is present west of coarse-grained volcaniclastic strata at the base of the Claron cliffs. Seismic reflection data indicate that the total displacement on the fault zone in this area is about 3000 feet (900 m) (Lundin, 1987, 1989; Davis, 1999).

Characteristic slip distribution and earthquake recurrence along the eastern Altyn Tagh fault revealed by high-resolution topographic data

AbstractThe seismic cycle model is roughly constrained by limited offset data sets from the eastern Altyn Tagh fault with a low slip rate. The recent availability of high-resolution topographic data from the eastern Altyn Tagh fault provides an opportunity to obtain distinctly improved quantitative, dense measurements of fault offsets. In this paper, we used airborne light detection and ranging data and unmanned aircraft vehicle photogrammetry to evaluate fault offsets. To better constrain the large earthquake recurrence model, we acquired dense data sets of fault displacements using the LaDiCaoz_v2.1 software. A total of 321 offset measurements below 30 m highlight two new observations: (1) surface-slip of the most recent earthquake and multiple events exhibit both short-wavelength (m-scale) and long-wavelength (km-scale) variability; and (2) synthesis of offset frequency analysis and coefficient of variation indicate regular slip events with ∼6 m slip increment on fault segments to the west of the Shulehe triple junction. The distribution of offsets and paleoseismological data reveal that the eastern Altyn Tagh fault exhibits characteristic slip behavior, with the characteristic slip of ∼6 m and a recurrence period ranging from 1170 to 3790 years. Paleoearthquake recurrence intervals and slip increments yield mean horizontal slip-rate estimates of 2.1–2.6 mm/yr for fault segments to the west of the Shulehe triple junction. Assuming a 10 km rupture depth and a 30 GPa shear modulus, we estimated a characteristic slip event moment magnitude (Mw) of ∼7.6. Finally, we discuss the interaction mechanism between Altyn Tagh fault (strike fault) and the NW-trending thrust faults (reverse faults) that caused the sudden decrease of sinistral slip rate at the Shulehe and Subei triple junctions; our results support the eastward “lateral slip extrusion” model.

The Long Recurrence Intervals of Small Repeating Earthquakes May Be Due to the Slow Slip Rates of Small Fault Strands

AbstractObservations since 1998 have revealed that repeating earthquakes, and particularly small repeating earthquakes, occur less often than expected given their seismically derived slip and the regional fault slip rate. Here we test the hypothesis that small repeaters occur infrequently because they occur on fault segments or strands with low slip rates. We analyze the recurrence interval‐moment scaling of earthquake sequences near Parkfield, California. We find that closely spaced sequences, which likely occur on the same fault strand and respond to the same slip rate, follow a scaling consistent with seismic slip rates while widely spaced sequences, which likely occur on different strands, follow a scaling consistent with the previous counterintuitive observations. These results suggest that spatially varying slip rates could create the recurrence interval scaling, though we cannot exclude other explanations.

Implications of basement rock alteration in the Nankai Trough, Japan for subduction megathrust slip behavior

The Nankai Trough is an exceptionally well-studied convergent margin known to host damaging megathrust earthquakes as well as various forms of slow fault slip. Outcrop studies of exhumed analogues for the modern subduction thrust, as well as seismic reflection images of the active subduction zone, suggest that the basaltic basement participates in plate-boundary shearing at depths of a few km and greater. We obtained altered basaltic upper basement from the modern Nankai Trough seaward of the trench, recovered by drilling on IODP Expedition 333. We performed laboratory friction experiments on bare surfaces and gouge powders of this material, in addition to and in combination with other materials for comparison. The altered basalt exhibits predominantly velocity-strengthening frictional behavior, indicating a tendency for stable slip. For bare surface experiments, few instances of velocity-weakening friction occur and are restricted to slip rates of <10−6 m/s. Thin sections and XRD analyses of the starting material indicate that the velocity-strengthening behavior is likely associated with the presence of clay minerals, mostly Mg-smectite, which coat the rims of larger, stronger grains. Based our friction data, we suggest that in addition to creep the altered Nankai basalts may also allow the possibility of slow slip events for two reasons: (1) velocity-weakening friction may be expected at low slip rates, but velocity-strengthening at higher rates will damp any potential slip instabilities; and (2) based on a critical stiffness criterion for accelerating (stable) slip, SSEs are capable of nucleating in the altered Nankai basalt despite velocity-strengthening friction. In light of these observations, and given the depth at which altered basement appears to be incorporated along the plate interface, we raise the possibility that some shallow slow slip events in the Nankai accretionary prism could originate from shearing in altered basalt.

Constraining mountain front tectonic activity in extensional setting from geomorphology and Quaternary stratigraphy: A case study from the Matese ridge, southern Apennines

Rugged peaks, large intermontane basins and frequent seismicity all characterize the active extensional tectonic setting of the southern Apennines. The Matese ridge typifies the active tectonic setting of the southern Apennines with steep carbonate mountain fronts and large depositional centres. Moderate to high magnitude earthquakes have affected the northern, western and eastern sectors of the Matese ridge in historical times. However, the seismogenic potential of the extensional fault system bounding the southern Matese mountain front has not been fully assessed to date. To unravel the active tectonic setting of the southern Matese mountain front, we have carried out a comprehensive geomorphological and tectonic-geomorphology investigation of the mountain front and its piedmont and have constrained results through chronological (i.e., tephrostratigraphical and 40Ar/39Ar) and structural data.Our study highlights that in the last ∼600 ka, activity along E-W trending normal faults has identified a locus of higher slip rate tectonic activity in the central part of the analysed mountain front. These active E-W-striking normal faults are inherited, reactivated structures, which have interacted with newly formed NW-SE-striking normal faults during NE-SW extension active on the regional scale, causing fault bending and local extension to be oriented N-S. Consequently, lower slip rates have been recorded along the NW-SE-striking normal faults at the north-western and south-eastern tips of the southern Matese front. The long-term displacement rate of the fault system at the boundary of the central part of the southern Matese front is consistent with mean values of displacement of faults that, in the southern Apennines, show evidence of activity during the late Quaternary. Despite strong historical seismicity clustering primarily around the study area, our data highlight that it cannot be ruled out that moderate to high magnitude seismicity could affect the southern Matese mountain front.Our case study represents an example of the possible modes of formation and evolution of mountain front-basin systems in extensional setting, and shows how the combination of different data sets allows unravelling the interaction between tectonic, erosional and sedimentary processes, which lead to landscape evolution of active mountain belts.

Paleoearthquake History Along the Southern Segment of the Daliangshan Fault Zone in the Southeastern Tibetan Plateau

AbstractAssessing the seismic hazard of a fault is usually based on its record of strong earthquakes. Earthquake records with long periods of quiescence for active faults can lead to underestimates of seismic hazards, such as for the Longmenshan fault zone which produced the unanticipated 2008Mw7.9 Wenchuan earthquake. The Daliangshan fault zone has a low slip rate and has not produced any strong earthquakes in history. As a result, little is known about its paleoearthquake history, including the behavior of any strong earthquakes it might produce and the seismic hazards posed by the Daliangshan fault zone. To solve this problem, we excavated four trenches across the Jiaojihe and Butuo faults along the southern segment of the Daliangshan fault zone. The paleoseismic investigations revealed six paleoearthquakes on the Jiaojihe fault in ~20,000 years and determined another seven rupturing events on the Butuo fault in ~42,000 years. The strong earthquake history of the Jiaojihe fault has evidence of temporal clustering, while the Butuo fault exhibits a relatively periodic recurrence pattern with intervals of 1,710–2,460 years. Based on its surface rupture length and the magnitude of observed displacement, the southern segment of the Daliangshan fault zone is capable of producingM &gt; 6.5 earthquakes. Furthermore, based on their respective slip rates and the elapsed times since the most recent events along the Jiaojihe and Butuo faults, they have accumulated seismic energy equivalent toM ~ 7.6, suggesting they pose a significant seismic hazard to the southeastern Tibetan Plateau.

Evidence of long recurrence times and low slip rate along the 1668 Tancheng earthquake fault

Fault slip rates and recurrence intervals of large earthquakes for active faults are important parameters for better understanding active faults and assessing their seismic hazard. The Tanlu fault, located in the densely populated and economically developed area of eastern China is thought to be the source of the M 7 Anqiu earthquake in 70 BC, and M 8½ Tancheng earthquake in 1668. Understanding the recurrence interval of paleoearthquakes and fault slip rates for the Tancheng earthquake fault is critical for assessing the potential for seismic risk and assessment for the Tanlu fault. However, the only published study used several trenches and a single trench does not completely record the sequence of paleoearthquake events, leaving a large uncertainty of seismic hazard. GPS observations in North China show that there is no significant velocity gradient across the Tanlu fault, yet the long-term slip rate of the Tancheng segment of the fault is estimated to be significantly higher, up to 2 mm/a. Therefore, it is critical to conduct further research on the paleoearthquake history and slip rates of this fault segment to reconcile these contrasting results. In this study, we utilize aerial photographs and high-resolution satellite imagery, combined with field investigations of a surface rupture formed by the 1668 earthquake. The earthquake rupture is ~80 m long and ~2.5 m high, located in the Huaqiao village of northeastern Tancheng County. A gully across the rupture reveals a right lateral dislocation of approximately 36 m. We excavated two trenches on both sides of the rupture. Trench 1 reveals a positive flower structure and is consistent with a right lateral strike-slip fault with a thrust component consistent with the modern regional stress field. Trench 2 reveals a colluvial wedge formed by the latest paleoearthquake with a fine-grained deposit overlapping the colluvial wedge. The latest paleoearthquake should occur prior to deposition of the fine-grained deposit. AMS-14C radiocarbon dating was used to determine the age of the event and is approximately 12.8 +4.0/−3.7 ka, indicating a recurrence interval of large earthquakes greater than 10 ka, consistent with the results from other segments of the Tanlu fault. Combined with an average slip of ~9 m for the 1668 Tancheng earthquake, the dextral slip rate along the Tancheng earthquake fault since the end of the late Pleistocene is estimated to be 0.7 mm/a, consistent with low interseismic strain accumulation based on geodetic observations across the North China region.

Modeling of fault slip during hydraulic stimulation in a naturally fractured medium

Assessing the intensity of potential seismicity induced by fault slip is a mandatory task in the development of enhanced geothermal systems. In this paper numerical simulations are performed to investigate the propagation of hydraulic fractures and the slip behavior of existing faults due to fluid injection. The cohesive zone model is used in combination with finite cohesive elements to model the hydraulic fractures and the existing faults while the fault shear strength is assumed to follow the Coulomb friction law. Our focus is on the role of the friction conditions on the fault slip behavior. The simulation results show that faults with small friction coefficients tend to slip at low slip rates while faults with a higher friction coefficient tend to slip at rates that are higher than the unstable slip rate threshold. It is also demonstrated that under specific frictional conditions, the sequential stimulation mechanism of permeability enhancement is possible. The results suggest that a good characterization of the fault frictional conditions is required to successfully predict the fault slip pattern and that lowering the fault friction coefficient could potentially reduce the fault slip rate.

Kinematics of southern California crustal deformation: Insights from finite-element models

Two sets of finite-element model suites were developed to address discrepancies between geodetic and geologic fault slip rates in southern California, as well as the extent of “off-fault” deformation that does not result from interseismic elastic strain around known, locked faults. The GPS-constrained models represent current deformation, while the strain energy rate (TSE) minimizing models represent a long-term average of deformation that has occurred over thousands to millions of years. Both classes of models suggest low slip rates (<29 mm/yr) for the San Andreas Fault (SAF) in the Mojave and Big Bend regions. A summed slip rate of less than 8 mm/yr is also inferred for thrust faults accommodating shortening across the Transverse Ranges. GPS-constrained, locked models suggest high slip rates for the Imperial Fault and the Coachella SAF (>35 mm/yr and >32 mm/yr) but TSE-constrained, unlocked models suggest much lower slip rates for these two faults. All models are consistent with strain transfer from the SAF Coachella segment to the Eastern California Shear Zone, bypassing the SAF, but the GPS-constrained models suggest this far more strongly. This would seem to support variations in rates of fault slip and regional deformation patterns over millennial timescales, but the comparable Mojave SAF slip rates for both model classes is inconsistent with this hypothesis. Assuming a “propeller” geometry for the SAF (Fuis et al., 2012, 2017) does not alter inferred slip rates. Correcting the GPS velocity field for seismic cycle effects associated with large earthquakes on the 1857 SAF rupture segment increases the inferred slip rate of the Mojave South segment of the San Andreas fault by up to about 5 mm/yr. “Off-fault” deformation accounts for 38% of the total moment accumulation in the preferred GPS-constrained model, broadly consistent with previous estimates.

Late Quaternary Activity of the La Rinconada Fault Zone, San Juan, Argentina

AbstractMost of the permanent deformation in the Pampean Flat slab segment of the central Andes is taken up at the Andean Orogenic Front in Argentina, a narrow zone between the Eastern Precordillera and Sierras Pampeanas that comprises one of the world's most seismically active thrust zones. Active faults and folds in the region have been extensively mapped but still largely lack information on style and rates of deformation, which is essential for understanding the distribution of regional strain and estimating the seismic potential of individual faults. Structural, geomorphic, and 36Cl cosmogenic radionuclide surface exposure age methods are used to focus on key sites along the 30‐km‐long La Rinconada Fault Zone in this region of west‐central Argentina, which is ~15 km away from the highly populated (~500,000) city of San Juan, to define a late Quaternary average shortening rate of 0.41 ± 0.01 mm/year. This slip rate is the same order of magnitude, but slightly lower than nearby similar east dipping Eastern Precordillera faults including the La Laja and Las Tapias Faults. Relatively low slip rates are interpreted as being a consequence of distributed deformation between the latitude of the La Rinconada Fault Zone (31 and 32°S), as compared to between latitudes 32 to 33°S where deformation appears to be focused on fewer structures, including the Las Peñas and La Cal Thrust Faults. The La Rinconada Fault Zone is capable of generating earthquakes of Mw 6.6–7.2, but further investigations are required to determine timing and recurrence intervals of discrete events.

The tectono-sedimentary evolution of a major seismogenic zone with low slip rate activity: A geochronological and sedimentological investigation of the Dobrá Voda Depression (Western Carpathians)

Seismically active fault zones receive a great deal of attention due to their potential for quantification of seismic hazards. Zones with low slip rates pose a challenge, however, since their poor topographic expression is related to difficulties in the quantification of fault movement. This study focuses on the Dobrá Voda Depression, an area with the highest level of seismic activity in the Western Carpathians. The Quaternary tectono-sedimentary evolution of the small intramontane basin was investigated with the use of facies analysis of cores, dated with the use of cosmogenic nuclide depth profiles (10Be, 26Al and 36Cl), together with 26Al/10Be burial dating and radiocarbon dating. A set of archived boreholes and geoelectric survey data was used for the correlation of results with those from new boreholes across the depression. Four facies associations were distinguished: (FA1) Colluvial deposits that comprise subaerial debris flows and mudflows; (FA2) Fluvial deposits with high sediment supply: accommodation ratio, composed mostly of sandy-gravelly channel fill facies; (FA3) Fluvial deposits with low sediment supply: accommodation ratio, consisting mostly of floodplain muds, overbank heterolithic facies and minor sandy-gravelly channel fills; and (FA4) Swamp deposits, which are mostly made up of peat. Geochronological results suggest that the studied part of FA3 was deposited before 1.0 Ma due to a rise in the base level following a major incision event. Overbank-dominated deposits of FA3 covered an incision surface, resulted in a difference of ca. 65 m of elevation of these strata, which represents the minimal thickness of FA3. The second phase of incision was related to reactivation of Miocene normal faults resulting in further topographic differentiation. The initiation of fault activity is recorded by the deposition of colluvial FA1 before ca. 250 ka. FA2 accumulated between ca. 160 and 100 ka, mostly at the toes of slopes bounding the fault scarps on the basin margins. The last documented phase of evolution represents an increase of accommodation, which was connected to the deposition of Holocene peat in swamps as well as floodplain muds of FA4 above FA2. The observed settings imply that variation between incision and accumulation in a scale of hundreds of thousands of years is characteristic for low relief tectonically active zones. The presented research demonstrates the significance of sedimentological analysis for reconstruction of tectonic evolution in areas with low slip rate activity.

Tectonic topography and Late Pleistocene activity of the West Qinling Fault, northeastern Tibetan Plateau

A precise measurement of the slip rate of active faults within and around the Tibetan Plateau will provide definite and explicit knowledge of continental dynamics and present-day active tectonic processes. The WNW-trending West Qinling Fault (WQLF), the target of this study, is one of the major active strike-slip faults developed in the northeastern Tibetan Plateau. The interpretation of three dimension (3D) perspective topographic maps, field investigations, and 14C-dating results reveal that (i) the drainage systems, mountain ridges, alluvial fans, and terrace risers have been systematically left-lateral deflected or offset by ∼6 m up to hundreds of meters during the Late Pleistocene–Holocene along the WQLF in the northeastern marginal zone of the Tibetan Plateau; (ii) the left-lateral strike-slip rate is estimated to be ∼2.5–2.9 mm/yr with an average value of ∼2.7 mm/yr since the Late Pleistocene; (iii) compared to the well-studied strike-slip active faults developed in the northern and northwestern Tibetan Plateau such as the Altyn Tagh Fault and the Kunlun Fault with high slip rate of >10–20 mm/yr, the WQLF displays a characteristically low strike-slip rate of <3 mm/yr. We interpret that the low slip rate of the WQLF is related to the limited convergence transfer and that most of the strain energy was probably absorbed and partitioned by continuous crustal deformation in the northeastern marginal zone of the Tibetan Plateau, rather than only the localized deformation along active faults.