Low Slip Rates Research Articles

A Synthesis of Fracture, Friction and Damage Processes in Earthquake Rupture Zones

We review properties and processes of earthquake rupture zones based on field studies, laboratory observations, theoretical models and simulations, with the goal of assessing the possible dominance of different processes in different parts of the rupture and validity of commonly used models. Rupture zones may be divided into front, intermediate, and tail regions that interact to different extents. The rupture front is dominated by fracturing and granulation processes and strong dilatation, producing faulting products that are reworked by subsequent sliding behind. The intermediate region sustains primarily frictional sliding with relatively high slip rates that produce appreciable stress transfer to the propagating front. The tail region further behind is characterized by low slip rates that effectively do not influence the propagating front, although it (and the intermediate region) can spawn small offspring rupture fronts. Wave-mediated stress transfer can also trigger failures ahead of the rupture front. Earthquake ruptures are often spatially discontinuous and intermittent with a hierarchy of asperity and segment sizes that radiate waves with different tensorial compositions and frequency bands. While different deformation processes dominating parts of the rupture zones can be treated effectively with existing constitutive relations, a more appropriate analysis of earthquake processes would require a model that combines aspects of fracture, damage-breakage, and frictional frameworks.

Soil Compaction under Different Traction Resistance Conditions—A Case Study in North Italy

Tractive efficiency is essential in tillage operations to optimise traction performance. In this field experiment, the tractor performance was measured under different traction resistance conditions. This study quantified the soil stress, soil bulk density, soil moisture, soil cone index, soil surface disturbance, rolling resistance and slip rate under different numbers of passes and traction conditions. The actual power used under different soil and traction conditions was collected. Fuel consumption and savings were calculated between uncompacted soil, compacted soil and the permanent traffic lane. The results show that soil stress increases in each location as traction and the number of passes increase. Soil’s physical properties increase, such as the soil bulk density, soil cone index and soil surface disturbance. Additionally, the slip rate increases with traction in each soil condition as uncompacted soil, compacted soil and the permanent traffic lane. The results show that the permanent traffic lane has a lower slip rate under different traction conditions than the uncompacted and compacted soil. Furthermore, the permanent traffic lane has less energy consumption with the same traction resistance. The permanent traffic lane saved 25.50%, 29.23% and 42.34% fuel compared to the uncompacted field in 7.85, 14.71 and 24.52 kN traction conditions, respectively. Our results confirm that dynamic factors such as traction and rolling resistance should be considered in soil compaction research rather than static weight only. In practice, the controlled traffic farming (CTF) system or driving the tractor more frequently on the permanent traffic lane should be considered to improve working efficiency and reduce energy consumption.

Geologic and geodetic constraints on the magnitude and frequency of earthquakes along Malawi's active faults: the Malawi Seismogenic Source Model (MSSM)

Abstract. Active fault data are commonly used in seismic hazard assessments, but there are challenges in deriving the slip rate, geometry, and frequency of earthquakes along active faults. Herein, we present the open-access geospatial Malawi Seismogenic Source Model (MSSM; https://doi.org/10.5281/zenodo.5599616), which describes the seismogenic properties of faults that formed during ongoing east African rifting in Malawi. We first use empirically derived constraints to geometrically classify active faults into section, fault, and multifault seismogenic sources. For sources in the North Basin of Lake Malawi, slip rates can be derived from the vertical offset of a seismic reflector that dated lake cores indicate is 75 ka. Elsewhere, slip rates are constrained from advancing a systems-based approach that partitions geodetically derived rift extension rates in Malawi between seismogenic sources using a priori constraints on a regional strain distribution and a hanging wall flexural extension in magma-poor continental rifts. Slip rates are then combined with source geometry and empirical scaling relationships to estimate earthquake magnitudes and recurrence intervals, and their uncertainty is described from the variability in logic tree outcomes used in these calculations. Sources in the MSSM are 5–269 km long, which implies that large-magnitude (Mw 7–8) earthquakes may occur in Malawi. However, low slip rates (0.05–2 mm yr−1) mean that the frequency of such events will be low (recurrence intervals of ∼103–104 years). We also find that, for 9 out of 11 faults in Lake Malawi's North Basin, differences in the slip rates, when estimated independently from the geodetic data and the offset seismic reflector, are not statistically significant. The MSSM represents an important resource for investigating Malawi's increasing seismic risk and provides a framework for incorporating active fault data into seismic hazard assessment elsewhere in the East African Rift and other tectonically active regions.

Evaluation of the Soil Thrust on Continuous Tracks Considering Independent Soil Shearing by Grousers

Soil thrust is a traction force of an off-road tracked vehicle. Existing soil thrust assessment methods assume that a continuous shear failure plane exists along the soil-track interface. However, recent experimental works revealed that the soil beneath the track is divided into soil blocks; each soil block is sheared independently. This study proposed a new total soil thrust assessment method based on the block-shaped failure mechanism, and the total soil thrust predicted by the proposed and the existing methods was compared. The results showed that the existing method showed a greater maximum soil thrust at a lower slip rate than the proposed method. When the soil exhibited a hardening behavior, the total soil thrust in the existing method was always greater than that in the proposed method. However, when the soil exhibited softening behavior or hump behavior, the total soil thrust in the existing method was greater than that in the proposed method until a specific slip ratio, after which the latter became greater. Unlike the existing method, the proposed method can consider the difference in soil thrust with the grouser shape ratio, showing that the total soil thrust increased as the grouser height increased and the shape ratio decreased.

Multiple Mw≥6.5 Strong-Major Paleoearthquakes Occurred Before the 2017 Mw 6.3 Jinghe Earthquake: Evidence from Trenching the Jinghenan Fault

AbstractPartial fault segment rupture may increase local earthquake hazards. To verify whether a strong earthquake will occur after the lower ramp rupture 2017 v6.3 Jinghe earthquake, we excavated a trench at the east segment of the fault near the Xiatianji reservoir. Integrating the trench wall interpretation and stratigraphic optically stimulated luminescence (OSL) ages, we constrain four paleoearthquakes. They are named E1–E4 from the oldest to the youngest and occurred at 29.8 ± 3.0, 22.4 ± 1.9, 14.7 ± 1.9, and after 11.6 ± 0.9 ka B.P., respectively. The average recurrence interval between E1, E2, and E3 is 7.3 ± 0.7 ka B.P. This recurrence interval may have exceeded the elapsed time since the most recent surface rupturing earthquake. The overlap between the last event and the average recurrence interval may indicate that the time since the most recent event reaches the recurrence interval, and a major earthquake (7 < M < 8) may yet occur after the 2017 Jinghe event. Most historical and instrumental major great earthquakes occurred on higher slip rate faults at the northern and southern piedmont of Tian Shan. The low slip rate thrusts within the Tian Shan also have the potential to generate major earthquakes.

3D geomechanical modeling of the Xianshuihe fault zone, SE Tibetan Plateau: Implications for seismic hazard assessment

The Xianshuihe fault on the southeastern margin of the Tibetan Plateau is one of the most active intracontinental faults worldwide. At least 16 strong earthquakes (M > 6.5) have occurred on this fault since 1327 CE. To reasonably assess the future seismic hazard of this fault region, it is essential to gain a comprehensive knowledge of the fault kinematics and stress state. In this study, we developed a fine 3D geomechanical model of the Xianshuihe fault and its adjacent area, and obtained a spatially continuous contemporary kinematics and crustal background stress field of this region. Our modeled results show that the slip rate of the Xianshuihe fault is as high as 11 mm/a on the northwestern segment and generally decreases to ~9 mm/a on the southeastern segment (i.e. Moxi fault). The Yulongxi fault, a branch oblique to the Moxi fault, has different slip senses in different segments with a very low horizontal slip rate (<0.6 mm/a). In terms of stress, the study area is dominated by a transtensional faulting stress regime with E-W-trending maximum horizontal stress SH, indicating the study area is mainly subjected to an E-W compression and N-S extension. Localized normal and thrust faulting regimes appear alternately along the Xianshuihe fault, showing an inhomogeneous stress state. The high normal stresses on the Songlinkou-Selaha segment and the Moxi fault combined with their relatively high slip rates, make us speculate that these two segments have the potential to produce strong earthquakes in the future. A relatively high seismic hazard is also ascribed to the Yulongxi fault based on the analysis of its geological and geodynamic environment.

Nucleation mechanism of the 2021 Mw 7.4 Maduo earthquake, NE Tibetan Plateau: Insights from seismic tomography and numerical modeling

The 2021 Mw 7.4 Maduo earthquake ruptured the Jiangcuo fault, a secondary fault within the Bayan Har block, NE Tibetan Plateau, which attests that large earthquakes can occur on faults with very low slip rates. In this study, we use data from local seismic stations to explore the 3D velocity structure beneath the source region of the Maduo earthquake. Our results indicate that there is a distinct low-velocity anomaly in the mid-lower crust, and the thickness of this low-velocity zone decreases sharply to the east. The Maduo earthquake occurred in the transition zone between the high- and low-velocity regions. Based on our local velocity model and our knowledge of the regional crustal structures, we constructed numerical models to investigate the stress and strain energy distributions in our study area. As indicated by the stress concentration, strain energy accumulation, and low strain rate in the shallow upper crust around the source region, we conclude that the seismic velocity heterogeneity and the weak ductile mid-lower crust provide a unique tectonic environment that facilitated the nucleation of the Maduo earthquake. This study helps to understand the mechanisms of the Maduo earthquake, and more importantly reconciles the seeming contradiction between large earthquakes and low slip and strain rates.

Frictional constitutive behavior of chlorite at low shearing rates and hydrothermal conditions

Chlorite is a common, but understudied phyllosilicate mineral along continental and subduction zone faults. To understand the potential role of chlorite in different modes of fault slip, we measure the constitutive frictional properties of chlorite at low rates of deformation and shallow hydrothermal conditions by shearing powdered samples of water-saturated chlorite in the triaxial saw-cut configuration. Experiments were conducted at 25 to 130 °C, 130 MPa confining pressure, pore pressures from 10 MPa to 120 MPa, slip rates from 0.001 to 10 μm/s, and shear displacements up to 7.5 mm. The frictional strength of chlorite increases with increasing temperature from 25 to 130 °C (μ = 0.4 to 0.46), accompanied by an increased abundance of Riedel shears. Chlorite also transitions from rate-strengthening behavior at fast slip rates (0.1 to 10 μm/s) to rate-weakening or rate-neutral behavior at lower slip rates (0.001 to 0.01 μm/s), consistent with one hypothesis for the cause of slow slip. This transition in frictional behavior reflects different microphysical processes controlling the direct and evolution effects of friction. At low deformation rates, the magnitude and temperature sensitivity of the direct effect (a) are consistent with subcritical fracture. In contrast, the evolution effect (b) is insensitive to temperature and increases systematically with decreasing strain rate. We propose the increase in b and resulting rate-weakening behavior of chlorite with decreasing slip rate is controlled by time-dependent properties of adsorbed water to mineral surfaces.

Intermittent lab earthquakes in dynamically weakening fault gouge.

Large and destructive earthquakes on mature faults in Earth's crust occur as slip in a layer of a fine granular material-fault gouge-produced by comminution during sliding1,2. A range of insights into the frictional resistance of faults-one of the main factors controlling earthquake nucleation, dynamic propagation and arrest, and hence the destructive ground shaking of earthquakes2,3-has been obtained in experiments with spatially uniform slip imposed in small samples2,4-21. However, how various features of gouge friction combine to determine spontaneous progression of earthquakes is difficult to study in the lab owing to substantial challenges with sample sizes and adequate imaging22. Here, using lab experiments, we show that spontaneously propagating dynamic ruptures navigate a fault region with fine rock gouge through complex, intermittent slip processes with dramatic friction evolution. These include repeated arrest of rupture propagation caused by friction strengthening at lower slip rates and dynamic earthquake re-nucleation enabled by pronounced rapid friction weakening at higher slip rates consistent with flash heating8,12,23. The spontaneous repeated weakening and strengthening of friction in fine rock gouge highlights the fundamental dependence of friction on slip rate and associated processes, such as shear heating, localization and delocalization of shear, and dilation and compaction of the shear layer6,7,9-21. Our findings expand experimental support9,11 of the concept that co-seismic weakening may enable earthquake rupture to break through stable fault regions24,25, with substantial implications for seismic hazard.

Stick-slip behavior of a clayey crustal fault

Recent studies have revealed that slip on clay-rich fault planes, which develop in the shallow crust and can cause huge earthquakes, is controlled by their flow properties rather than their frictional properties. Here, we simulate a seismogenic crustal fault and show that such a fault plane may behave as a thixotropic yield stress fluid. We then conduct numerical experiments using a simple spring-slider model that incorporates this thixotropic property, and we successfully reproduce spontaneous stick-slip behaviors that correspond to a variety of seismogenic processes, ranging from regular earthquakes with high slip rates to slow earthquakes with lower slip rates. This finding suggests that the seismic activity on a shallow clay-rich crustal fault may be governed by the time-evolving microstructure of the clay-water system that exists along the fault plane.

Улаанбаатар Орчмын “Сонгино” Идэвхитэй Хагарал Дээрхи Георадарын Судалгааны Анхан Шатны Үр Дүнгээс

The seismic activity observed in the vicinity of Ulaanbaatar (UB) city not only has been increased since 2005, but it is also organized, at least, on two perpendicular directions which determine two active faults: Emeelt fault (40 km long, situated 15 km NW of UB) and Hustai fault (80 km long, less than 30 km West of UB). The Songino fault (10 km long, situated 20 km West of UB) is located between Emeelt and Hustai fault. Their length and morphology indicate they can produce earthquakes of magnitude 6.5 to 7.5. Most of the Mongolian population (1.5 million over 3 million) is concentrated around UB city which is the main political and economical centre of the country. Hence, the study of seismic hazard is of first importance for the country. Since the last large earthquake, the fault geomorphology has been smoothed due to erosion processes and a low slip rate. The exact location of the fault is thus hidden in a several meter strip. In such a context, the Ground Penetrating Radar (GPR) method gives good and useful results and can help to characterize faults by identifying offsets of radar reflectionsand buried fluvial channel deposits. In order to image and characterize these faults, we have conducted many GPR campaigns in 2010, 2012 and 2013 over active areas around UB. In our study we present only some preliminary results of GPR measurements performed along the Songino fault (in 2013). The objective is to understand its geometry (dip, length, orientation) and the type of displacements and amplitude. In this survey we used 250 MHz, 500 MHz shielded antenna and RTA 50 MHz unshielded antenna and also used a differential GPS in order to measure the topography. One trench has been dug in Songino area.

A Continuous 13.3-Ka Paleoseismic Record Constrains Major Earthquake Recurrence in the Longmen Shan Collision Zone

Thrust collision zones with low slip rates along the plate boundary are significant areas of stress accumulation and prone to develop more destructive earthquakes with longer recurrence intervals. Such regions are often classified as low seismic risk if they lack continuous records of large earthquakes, such as the eastern Tibetan Plateau before the 2008 Mw 7.9 Wenchuan earthquake. Here, we provide a continuous seismic record in the Longmen Shan thrust fault zone spanning 13,000 years based on detailed investigation of the soft-sediment deformation structures and seismites in the Lixian lacustrine sequence. The recurrence time of large earthquakes (M ≥ 8.1) is 1,200 years, which is significantly shorter than the previous estimate of 2,000–6,000 years. The Maoxian-Wenchuan fault is the main fault that triggered the deformation in the Lixian lacustrine sediments. In addition, earthquake recurrence in the warm period is more frequent than that in the cold period, which should arouse our attention for the seismic study of tectonically active regions.

Interseismic Strain Accumulation Across the Main Recent Fault, SW Iran, From Sentinel‐1 InSAR Observations

AbstractThe Main Recent Fault is a major right‐lateral strike‐slip fault in the western Zagros mountains of Iran. Recent geodetic and geological studies estimate a low slip rate of 1–6 mm/yr at an unknown depth which, when combined with a non‐ideal fault geometry, makes the Main Recent Fault a difficult but interesting target for InSAR analysis. This analysis would further cement the estimated slip rate and provide an opportunity of estimate the depth to the base of the locked seismogenic zone, both important constraints on the seismic hazard posed by the fault, as well as for understanding how oblique convergence is accommodated and partitioned across the Zagros. We use 200 Sentinel‐1 SAR images from the past 5 years, spanning two ascending and two descending tracks, to estimate the first InSAR‐derived slip rate and locking depth for a 300 km long section of the fault. We utilize two established processing systems, LiCSAR and LiCSBAS, to produce interferograms and perform time series analysis, respectively. We constrain north‐south motion using GNSS observations, decompose our InSAR line‐of‐sight velocities into fault‐parallel and vertical motion, and fit 1‐D screw dislocation models to three fault‐perpendicular profiles of fault‐parallel velocity, following a Bayesian approach to estimate the posterior probability distribution on the fault parameters. We estimate an interseismic slip velocity of 2.4 ± 1.2 mm/yr below a loosely constrained 14 km locking depth, the first such estimate for the fault, and discuss the challenges in constraining the locking depth for low magnitude interseismic signals.

Thirty years of paleoseismic research in metropolitan France

A critical review is conducted of a selection of paleoseismic works published on, or close to, metropolitan France over the last 30 years. The evolution of these works may be subdivided into three periods: dawn of French paleoseismic studies (≈1990–1995), beginning of a multidisciplinary paleoseismologic approach, and paleoseismic studies in the first decades of the 21st century. This review of the most interesting paleoseismic studies at nine trench sites indicates that it is often difficult to associate Quaternary surface deformations with a well-identified fault. However, these studies also provided important results demonstrating that even in regions of low seismicity, seismic ruptures can repeat on the same low slip rate fault, thus providing evidence that historical seismicity is not sufficient to assess seismic hazard in metropolitan France. Finally, recommendations are provided for future paleoseismic investigations in low-seismicity regions.

Low‐Rate Faulting on the Margin of the Colorado Plateau and Rio Grande Rift in North‐Central New Mexico

AbstractIn northern New Mexico, seismic hazard outside of the Rio Grande Rift (RGR) is generally considered low due to limited historical seismicity and few mapped Quaternary faults. Although the region has a complex tectonic history, nearly all known faults are considered inactive because of a lack of faulted Quaternary deposits. Analysis of lidar and existing geologic and geomorphic mapping permits identification and characterization of four faults on the Colorado Plateau/RGR margin. The Gallina, Willow Creek, and East and West Brazos Peak faults are normal or dextral‐normal faults that strike NW‐SE with lengths from 15 to 50 km. The Willow Creek fault has scarp heights &lt;0.5–6.4 m on five Quaternary surfaces, with displacement increasing with relative surface age. An ∼5‐m‐high scarp on the ∼250 ka Brazos basalt yields an ∼0.02 mm/yr minimum dip‐slip rate. Oblique slip is recorded by dextral offset (∼40 m) of a middle Quaternary (?) terrace riser, a linear and en‐echelon stepping fault pattern, and a consistent down‐to‐the‐northeast fault expression. The West Brazos Peak fault displaces late Quaternary (?) surfaces by &lt;4 m down‐to‐the‐southwest. We interpret these faults are Laramide‐aged faults reactivated as normal or dextral‐oblique faults in the Quaternary, consistent with regional stress and geodetic data. Although the faults have low slip rates (&lt;0.1 mm/yr), the fault lengths suggest they may rupture in M6‐7 earthquakes and may pose a previously unrecognized seismic hazard to the region. Dextral transtension within the eastern Colorado Plateau is consistent with geodetic strain rates and earthquake focal mechanisms.

Earthquake Magnitude Distributions on Northern Caribbean Faults From Combinatorial Optimization Models

AbstractOn‐fault earthquake magnitude distributions are calculated for northern Caribbean faults using estimates of fault slip and regional seismicity parameters. Integer programming, a combinatorial optimization method, is used to determine the optimal spatial arrangement of earthquakes sampled from a truncated Gutenberg‐Richter distribution that minimizes the global misfit in slip rates on a complex fault system. Slip rates and their uncertainty on major faults are derived from a previously published GPS block model for the region, with fault traces determined from offshore geophysical mapping and previously published onshore studies. The optimal spatial arrangement of the sampled earthquakes is compared with the 500‐year history of earthquake observations. Rupture segmentation of the subduction interface along the Hispaniola‐Puerto Rico Trench (PRT) fault and seismic coupling on the PRT fault appear to exert the primary control over this spatial arrangement. Introducing a rupture barrier for the Hispaniola‐PRT fault northwest of Mona Passage, based on geophysical and seismicity observations, and assigning a low slip rate of 2 mm/yr on the PRT fault are most consistent with historical earthquakes in the region. The addition of low slip‐rate secondary faults as well as segmentation of the Hispaniola and Septentrional strike‐slip fault improves the consistency with historical seismicity. An important observation from the modeling is that varying the slip rate on the PRT fault and different segmentation scenarios result in significant changes to the optimal magnitude distribution on faults farther away. In general, optimal on‐fault magnitude distributions are more complex and inter‐dependent than is typically assumed in probabilistic seismic hazard analysis and probabilistic tsunami hazard analysis.

3D Linked Subduction, Dynamic Rupture, Tsunami, and Inundation Modeling: Dynamic Effects of Supershear and Tsunami Earthquakes, Hypocenter Location, and Shallow Fault Slip

Physics-based dynamic rupture models capture the variability of earthquake slip in space and time and can account for the structural complexity inherent to subduction zones. Here we link tsunami generation, propagation, and coastal inundation with 3D earthquake dynamic rupture (DR) models initialized using a 2D seismo-thermo-mechanical geodynamic (SC) model simulating both subduction dynamics and seismic cycles. We analyze a total of 15 subduction-initialized 3D dynamic rupture-tsunami scenarios in which the tsunami source arises from the time-dependent co-seismic seafloor displacements with flat bathymetry and inundation on a linearly sloping beach. We first vary the location of the hypocenter to generate 12 distinct unilateral and bilateral propagating earthquake scenarios. Large-scale fault topography leads to localized up- or downdip propagating supershear rupture depending on hypocentral depth. Albeit dynamic earthquakes differ (rupture speed, peak slip-rate, fault slip, bimaterial effects), the effects of hypocentral depth (25–40 km) on tsunami dynamics are negligible. Lateral hypocenter variations lead to small effects such as delayed wave arrival of up to 100 s and differences in tsunami amplitude of up to 0.4 m at the coast. We next analyse inundation on a coastline with complex topo-bathymetry which increases tsunami wave amplitudes up to ≈1.5 m compared to a linearly sloping beach. Motivated by structural heterogeneity in subduction zones, we analyse a scenario with increased Poisson's ratio of ν = 0.3 which results in close to double the amount of shallow fault slip, ≈1.5 m higher vertical seafloor displacement, and a difference of up to ≈1.5 m in coastal tsunami amplitudes. Lastly, we model a dynamic rupture “tsunami earthquake” with low rupture velocity and low peak slip rates but twice as high tsunami potential energy. We triple fracture energy which again doubles the amount of shallow fault slip, but also causes a 2 m higher vertical seafloor uplift and the highest coastal tsunami amplitude (≈7.5 m) and inundation area compared to all other scenarios. Our mechanically consistent analysis for a generic megathrust setting can provide building blocks toward using physics-based dynamic rupture modeling in Probabilistic Tsunami Hazard Analysis.

Geometric and kinematic evolution of the Jiali fault, eastern Himalayan Syntaxis

• New GPS data in the Eastern Himalayan Syntaxis. • The strike-slip rates of the western and middle segments of the Jiali fault are low. • The eastern segment of the Jiali fault no longer accommodates strike-slip motion. • Decrease in the slip rate of the Jiali fault coincides with new faults emergence. • The eastern segment of the Jiali fault seems to rotate clockwise. Large strike-slip faults play an important role in slip partitioning of the oblique convergence between the Indian plate and the Eurasian plate. The Karakorum-Jiali fault zone (KJFZ) is regarded as the southernmost major fault in the strike-slip faults system of the Tibetan plateau. The significance of the Jiali fault as the southern boundary of the eastward extrusion of the Tibetan plateau remains subject to debate due to the wide disagreements in its strike-slip rate. There is also a huge mismatch between its previously predicted low slip rate and the accommodation of the most significant compression in the frontal Eastern Himalayan Syntaxis. New GPS measurements suggest that the dextral strike-slip rate of the western segment, the middle segment, and the western part of the eastern segment of the Jiali fault is 5.0 ± 0.5 mm/yr, 2.4 ± 0.8 mm/yr, and 3.8 ± 0.9 mm/yr, respectively. As for the eastern segment of the Jiali fault, based on a two-dimensional elastic dislocation model, we search for the optimal solutions of the strike-slip rates along its two branch faults. They no longer accommodate strike-slip motion. But the diffuse active fault zone between the Mishimi and Puqu fault, inferred by the distribution of small earthquakes and systematic geologic mapping, may accommodate the strike slip motion with an estimated rate less than 5 mm/yr. Thus, it is predicted to have taken place the eastern segment. The eastern segment of the Jiali fault appears to have horizontally rotated clockwise around the Namche-Barwa Syntaxis.

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.