Resolving co- and early post-seismic slip variations of the 2021 MW 7.4 Madoi earthquake in east Bayan Har block with a block-wide distributed deformation mode from satellite synthetic aperture radar data

On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.

Co- and post-seismic slip analysis of the 2017 M_(W)7.3 Sarpol Zahab earthquake using Sentinel-1 data

The M_(w)7.3 Sarpol Zahab earthquake that occurred in the Zagros Fold-Thrust Belt(ZFTB) of Iran on November 12,2017 is the largest earthquake instrumentally recorded in the region.This earthquake provides an opportunity to investigate the slip behaviour and frictional properties of the fault,which is significant for assessing future seismic potential.In this study,we use Sentinel-1 images to map the coand post-seismic deformation to invert for the fault slip.The result indicates that most of the coseismic slip is buried in the depth range of 11-17 km,and the maximum slip is about 3.8 m at a depth of 15 km.The coseismic slip induces an increase of Coulomb stress in the unruptured area of the seismogenic fault plane,driving the afterslip.Based on the stress-driven afterslip,we obtain a frictional parameter of(ab)=(0.001-0.002) for the updip afterslip zone and(a-b)=0.0002 for the downdip afterslip zone in the framework of rate-and-state friction.The constitutive parameter(a-b) of the fault is very small,suggesting that the fault segments are close to velocity-neutral and may experience coseismic rupture.

足式机器人SLIP模型向上跳跃台阶的运动控制

由于存在地势起伏,台阶对足式机器人运动稳定性会带来较大挑战.弹簧负载倒立摆模型(SLIP)作为研究足式机器人的优良模板,能否完成向上跳跃台阶的动作与其腿部摆角,起跳位置和跳跃高度都有密切的关系.由于调整模型腿部摆角规律容易引发运动失效,故本文在算法中引入虚拟弹簧腿,根据虚拟弹簧腿的运行规律确定合理起跳位置,根据起跳位置来控制系统跳跃高度进而完成跳跃台阶的动作.最后利用仿真软件进行多组仿真,结果表明本文算法对起跳区间划分合理,对起跳高度控制精准,能够实现SLIP模型跳跃台阶前后的稳定运动.

液体润滑浸渍表面(SLIPS)船舶防污涂层最新研究进展

综述了近3年来关于液体润滑浸渍表面(SLIPS)船舶防污涂层的研究进展,特别是润滑液的选择与涂层的结构设计,以及这些因素如何影响涂层的整体性能,以期为未来的研究提供最新思路及研究方法。

Coseismic deformation and fault slip distribution of the 2023 M_(W)7.8 and M_(W)7.6 earthquakes in Türkiye

On February 6,2023,a devastating earthquake with a moment magnitude of M_(W)7.8 struck the town of Pazarcik in south-central Türkiye,followed by another powerful earthquake with a moment magnitude of M_(W)7.6 that struck the nearby city of Elbistan 9 h later.To study the characteristics of surface deformation caused by this event and the influence of fault rupture,this study calculated the static coseismic deformation of 56 stations and dynamic displacement waveforms of 15 stations using data from the Turkish national fixed global navigation satellite system(GNSS)network.A maximum static coseismic displacement of 0.38 m for the M_(W)7.8 Kahramanmaras earthquake was observed at station ANTE,36 km from the epicenter,and a maximum dynamic coseismic displacement of 4.4 m for the M_(W)7.6 Elbistan earthquake was observed at station EKZ1,5 km from the epicenter.The rupture-slip distributions of the two earthquakes were inverted using GNSS coseismic deformation as a constraint.The results showed that the Kahramanmaras earthquake rupture segment was distinct and exposed on the ground,resulting in significant rupture slip along the Amanos and Pazarcik fault segments of the East Anatolian Fault.The maximum slip in the Pazarcik fault segment was 10.7 m,and rupture occurred at depths of 0–15 km.In the Cardak fault region,the Elbistan earthquake caused significant ruptures at depths of 0–12 km,with the largest amount of slip reaching 11.6 m.The Coulomb stress change caused by the Kahramanmaras earthquake rupture along the Cardak fault segment was approximately 2 bars,and the area of increased Coulomb stress corresponded to the subsequent rupture region of the M_(W)7.6 earthquake.Thus,it is likely that the M_(W)7.8 earthquake triggered or promoted the M_(W)7.6 earthquake.Based on the cumulative stress impact of the M_(W)7.8 and M_(W)7.6 events,the southwestern segment of the East Anatolian Fault,specifically the Amanos fault segment,experienced a Coulomb rupture stress change exceeding 2 bars,warranting further attention to assess its future seismic hazard risk.

Revealing the role of pyramidal slip in the high ductility of Mg-Li alloy

The high ductility of Mg-Li alloy has been mainly ascribed to a high activity of pyramidal<c+a>slip to accommodate plastic strain.In the present study,however,a quantitative analysis reveals that Li-addition can only slightly stimulate the activation of pyramidal<c+a>slip under compression along the normal direction of a hot-rolled Mg-4.5 wt.%Li plate,with a relative activity of approximately 18%.Although the limited activity of pyramidal<c+a>slip alone cannot accommodate a large plastic strain,it effectively reduces the number of{10.11}−{10.12}double twins,which are believed to be favorable sites for crack initiation.The evidently reduced activity of double twins leads to a lower cracking tendency,and therefore improves ductility.

Experimental investigation on fluid-induced slip behavior of fault filled with fault gouge

Fault zones are usually filled with fault gouge and accompanied by fault water.The coupled effect of fault gouge and water significantly impacts the slip behavior of the fault,which may weaken the fault structure and further induce rupture propagation and earthquakes.In this study,we carried out a laboratory experiment to investigate the fluid-induced slip behavior of fault filled with gouge.The friction evolution characteristic associated with fluid pressure and effective stress was investigated during the slip process.In addition,the role transformation process of the gouge on the slip behavior of fault was revealed.The experimental result indicates that the friction on the filled fault surface is significantly affected by fault gouge.The rupture of the gouge promotes fault slip and the fluid pressure plays a vital role in the initiation of fault slip.The fault gouge enhances the shearing strength of the fault and acts as a barrier before the initial slip under fluid injection.Nevertheless,the fault gouge would accelerate the fault slip and transform into lubricant after the initial slip.

Effect of boundary slip on electroosmotic flow in a curved rectangular microchannel

The aim of this study is to numerically investigate the impact of boundary slip on electroosmotic flow(EOF) in curved rectangular microchannels. Navier slip boundary conditions were employed at the curved microchannel walls. The electric potential distribution was governed by the Poisson–Boltzmann equation, whereas the velocity distribution was determined by the Navier–Stokes equation. The finite-difference method was employed to solve these two equations. The detailed discussion focuses on the impact of the curvature ratio, electrokinetic width, aspect ratio and slip length on the velocity. The results indicate that the present problem is strongly dependent on these parameters. The results demonstrate that by varying the dimensionless slip length from 0.001 to 0.01 while maintaining a curvature ratio of 0.5 there is a twofold increase in the maximum velocity. Moreover, this increase becomes more pronounced at higher curvature ratios. In addition, the velocity difference between the inner and outer radial regions increases with increasing slip length. Therefore, the incorporation of the slip boundary condition results in an augmented velocity and a more non-uniform velocity distribution. The findings presented here offer valuable insights into the design and optimization of EOF performance in curved hydrophobic microchannels featuring rectangular cross-sections.

Co and postseismic fault slip models of the 2022 M_(W)6.7 Menyuan earthquake reveal conjugated faulting tectonics at the central section of the Lenglongling fault

The 2022 M_(W)6.7 Menyuan earthquake ruptured the western end of the Tianzhu seismic gap,providing an opportunity to study the regional seismogenic characteristics and seismic hazards.Here we use interferometric synthetic aperture radar(InSAR)and seismic data to study the mainshock rupture,early afterslip and the second largest aftershock of the 2022 Menyuan earthquake sequences.Our modeling results show that the mainshock ruptured the Lenglongling fault and the Tuolaishan fault with a maximum slip of~3 m.Rapid postseismic transient deformation occurred at the center of the Lenglongling fault.Our afterslip modeling reveals that the majority of afterslip occurred in the deeper part of the Lenglongling fault.A high-angle conjugated faulting event is found at the middle section of the Lenglongling fault.We use the stress inversion to investigate the possible triggering mechanism of the conjugated rupture event.The results indicate the maximum principal stress direction is in~222°,forming a~22°angle between the conjugated fault of second largest aftershock and the mainshock.The calculated normal stress changes indicate the region is within a pull-apart stress field,which favors such a conjugated rupturing event.Our study will help understand the rupture behavior of such kind of conjugated fault in other regions.

Interseismic slip distribution and locking characteristics of the mid-southern segment of the Tanlu fault zone

We employ the block negative dislocation model to invert the distribution of fault coupling and slip rate deficit on the different segments of the Tanlu(Tancheng-Lujiang) fault zone, according to the GPS horizontal velocity field from 1991 to 2007(the first phase) and 2013 to 2018(the second phase). By comparing the deformation characteristics results, we discuss the relationship between the deformation characteristics with the M earthquake in Japan. The results showed that the fault coupling rate of the northern section of Tancheng in the second phase reduced compared with that in the first phase. However, the results of the two phases showed that the northern section of Juxian still has a high coupling rate, a deep blocking depth, and a dextral compressive deficit, which is the enrapture section of the 1668 Tancheng earthquake. At the same time, the area strain results show that the strain rate of the central and eastern regions of the second phase is obviously enhanced compared with that of the first phase. The occurrence of the great earthquake in Japan has played a specific role in alleviating the strain accumulation in the middle and south sections of the Tanlu fault zone. The results of the maximum shear strain show that the shear strain in the middle section of the Tanlu fault zone in the second phase is weaker than that in the first phase, and the maximum shear strain in the southern section is stronger than that in the first phase. The fault coupling coefficient of the south Sihong to Jiashan section is high, and it is also the unruptured section of historical earthquakes. At the same time, small earthquakes in this area are not active and accumulate stress easily, so the future earthquake risk deserves attention.

Risk factors and clinical significance of posterior slip of the proximal vertebral body after lower lumbar fusion

BACKGROUND Adjacent segment disease(ASD)after fusion surgery is frequently manifests as a cranial segment instability,disc herniation,spinal canal stenosis,spondylolisthesis or retrolisthesis.The risk factors and mechanisms of ASD have been widely discussed but never clearly defined.AIM To investigate the risk factors and clinical significance of retrograde movement of the proximal vertebral body after lower lumbar fusion.METHODS This was a retrospective analysis of the clinical data of patients who underwent transforaminal lumbar interbody fusion surgery between September 2015 and July 2021 and who were followed up for more than 2 years.Ninety-one patients with degenerative lumbar diseases were included(22 males and 69 females),with an average age of 52.3 years(40-73 years).According to whether there was retrograde movement of the adjacent vertebral body on postoperative X-rays,the patients were divided into retrograde and nonretrograde groups.The sagittal parameters of the spine and pelvis were evaluated before surgery,after surgery,and at the final follow-up.At the same time,the Oswestry Disability Index(ODI)and Visual Analogue Scale(VAS)were used to evaluate the patients’quality of life.RESULTS Nineteen patients(20.9%)who experienced retrograde movement of proximal adjacent segments were included in this study.The pelvic incidence(PI)of the patients in the retrograde group were significantly higher than those of the patients in the nonretrograde group before surgery,after surgery and at the final follow-up(P<0.05).There was no significant difference in lumbar lordosis(LL)between the two groups before the operation,but LL in the retrograde group was significantly greater than that in the nonretrograde group postoperatively and at the final follow-up.No significant differences were detected in terms of the|PI–LL|,and there was no significant difference in the preoperative lordosis distribution index(LDI)between the two groups.The LDIs of the retrograde group were 68.1%±11.5%and 67.2%±11.9%,respectively,which were significantly lower than those of the nonretrograde group(75.7%±10.4%and 74.3%±9.4%,respectively)(P<0.05).Moreover,the patients in the retrograde group had a greater incidence of a LDI<50%than those in the nonretrograde group(P<0.05).There were no significant differences in the ODI or VAS scores between the two groups before the operation,but the ODI and VAS scores in the retrograde group were significantly worse than those in the nonretrograde group after the operation and at the last follow-up,(P<0.05).CONCLUSION The incidence of posterior slippage after lower lumbar fusion was approximately 20.9%.The risk factors are related to a higher PI and distribution of lumbar lordosis.When a patient has a high PI and insufficient reconstruction of the lower lumbar spine,adjacent segment compensation via posterior vertebral body slippage is one of the factors that significantly affects surgical outcomes.

An Overview of Formation Mechanism and Disaster Characteristics of Post-seismic Debris Flows Triggered by Subsequent Rainstorms in Wenchuan Earthquake Extremely Stricken Areas

The Wenchuan earthquake induced large amounts of debris flows and catastrophic incidents triggered by subsequent rainstorms occurred frequently in the past 6 rainy seasons, and thus resulted in serious casualties, huge economic loss and long-term impact. In this paper, post-seismic debris flows distributed in 10 Wenchuan earthquake extremely stricken counties were verified and debris flow database consisting of 609 debris flows was established based on detailed investigation organized by Land and Resources Department of Sichuan Province. Combined with database and related studies, the impact of Wenchuan earthquake on debris flows was analyzed. And then variation of formation conditions including rainfall threshold and landform condition was analyzed by contrasting pre-seismic and post-seismic debris flows. Followed are some typical viewpoints on initiation mechanism of post-seismic debris flows. In the end of this paper, characteristics of postseismic debris flows triggered by subsequent rainstorms were comprehensively summarized, such as regional group occurrence, high frequency, high viscosity, chain effect, huge dynamics, large scale and long duration. We hope this paper will be helpful in understanding the formation mechanism, disaster characteristics and prevention countermeasures of post-seismic debris flows in Wenchuan earthquake extremely stricken areas.

Co- and post-seismic vertical displacements of Wenchuan Ms8.0 earthquake near Beichuan

Co- and post-seismic vertical displacements of the Wenchuan earthquake derived from two measurements in 2008 and 2010 along two partly-damaged leveling lines near the epicenter show the following features： Co-seismic displacement at Beichuan-Yingxiu fault was as large as 4. 711 m near Beichuan, where the maximum observed fault offset was 5.1 m. In contrast, the observed co-seismic offset of the Qingchuan fault in Pingwu County was only 0. 064 m. During 2008 - 2010, the post-seismic displacement rate was 5 - 27 mm/a near Beichuan-Yingxiu fault in Beichuan area, 20.6 mrn/a at Jiangyou-Guangyuan fault near Dakang, and only 0.2 - 1.3 mm/a at Qingehuan fault near Gucheng.

Numerical simulation of influences of the earth medium's lateral heterogeneity on co- and post-seismic deformation

Many studies revealed that the Earth medium＇s lateral heterogeneity can cause considerable effects on the co- and post-seismic deformation field. In this study, the threedimensional finite element numerical method are adopted to quantify the effects of lateral heterogeneity caused by material parameters and fault dip angle on the co- and postseismic deformation in the near- and far-field. Our results show that： 1） the medium＇s lateral heterogeneity does affect the co-seismic deformation, with the effects increasing with the medium＇s lateral heterogeneity caused by material parameters; 2） the Lame parameters play a more dominant role than density in the effects caused by lateral heterogeneity; 3） when a fault＇s dip angle is smaller than 90, the effects of the medium＇s lateral heterogeneity on the hanging wall are greater than on the footwall; 4） the impact of lateral heterogeneity caused by the viscosity coefficient on the post-seismic deformation can affect a large area, including the near- and far-field.

Post-seismic relaxation from geodetic and seismic data

We have examined the aftershock sequence and the post-seismic deformation process of the Parkfield earthquake （2004, M = 6, California, USA） source area using GPS data. This event was chosen because of the possibility of joint analysis of data from the rather dense local GPS network （from SOPAC Internet archive） and of the availability of the rather detailed aftershock sequence data （http：]/www.ncedc.org[ ncedc[catalog-search.html）. The relaxation process of post-seismic deformation prolongs about the same 400 days as the seismic aftershock process does. Thus, the aftershock process and the relaxation process in deformation could be the different sides of the same process. It should be noted that the ratio of the released seismic energy and of the GPS obtained deformation is quite different for the main shock and for the aftershock stage. The ratio of the released seismic energy to the deformation value decreases essentially for the post-shock process. The similar change in the seismic energy[deformation value ratio is valid in a few other strong earthquakes. Thus, this decrease seems typical of aftershock sequences testifying for decrease of ratio of elastic to inelastic deformation in the process of post-shock relaxation when the source area appears to be mostly fractured after the main shock occurs, but the healing process had no yet sufficient time to develop.

The June 2022 Khost earthquake in southeastern Afghanistan:A complicated shallow slip event revealed with InSAR

On June 22,2022,the Mw6.2 earthquake in southeastern Afghanistan caused a severe disaster.We used the Sentinel-1A ascending and descending track images of the European Space Agency and interferometric synthetic aperture radar(In SAR)to obtain the coseismic surface deformation field of the earthquake,which showed that the earthquake caused complex ruptures of multiple faults and various types.Using the dislocation model of the elastic half-space,we determined the focal parameters and slip distribution on the fault plane of this event.The results reveal that:(1)the seismogenic fault of this event is an unknown fault on the northeastern edge of the Katawaz microblock;(2)The slip on the fault plane is mainly in the range of 0—8 km along the dip,with maximum slips about 2 m at a depth of 2 km,which projected on the surface is 69.44°E,32.96°N.This event suggests that,similar to the Chaman,Ghazaband and other large faults,the faults inside the microblock also play an important role in adjusting for the collision stress between India and Europe.

Wall slip behavior of cemented paste backfill slurry during pipeline based on noncontact experimental detection

Wall slip is a microscopic phenomenon of cemented paste backfill(CPB)slurry near the pipe wall,which has an important influence on the form of slurry pipe transport flow and velocity distribution.Directly probing the wall slip characteristics using conventional experimental methods is difficult.Therefore,this paper established a noncontact experimental platform for monitoring the microscopic slip layer of CPB pipeline transport independently based on particle image velocimetry(PIV)and analyzed the effects of slurry temperature,pipe diameter,solid concentration,and slurry flow on the wall slip velocity of the CPB slurry,which refined the theory of the effect of wall slip characteristics on pipeline transport.The results showed that the CPB slurry had an extensive slip layer at the pipe wall with significant wall slip.High slurry temperature improved the degree of particle Brownian motion within the slurry and enhanced the wall slip effect.Increasing the pipe diameter was not conducive to the formation of the slurry slip layer and led to a transition in the CPB slurry flow pattern.The increase in the solid concentration raised the interlayer shear effect of CPB slurry flow and the slip velocity.The slip velocity value increased from 0.025 to 0.056 m·s^(-1)when the solid content improved from 55wt%to 65wt%.When slurry flow increased,the CPB slurry flocculation structure changed,which affected the slip velocity,and the best effect of slip layer resistance reduction was achieved when the transported flow rate was 1.01 m^(3)·h^(-1).The results had important theoretical significance for improving the stability and economy of the CPB slurry in the pipeline.

Loading direction dependence of asymmetric response of pyramidal slip in rolled AZ31 magnesium alloy

Textured magnesium alloys usually exhibit anisotropic mechanical behavior due to the asymmetric activation of different twinning and slipping modes.This work focuses on the pyramidal slip responses of rolled AZ31 magnesium alloy under two loading conditions,compressive and tensile loading along the normal direction.Under the condition where the compressive loading direction is closely parallel to the c-axis of the unit cell,tensile twinning and basal slips are prohibited, dislocations then active and tend to accumulate at grain boundaries and form dislocation walls.Meanwhile,these dislocations exhibit zigzag morphologies,which result from the cross-slip from {10■1} first-order pyramidal plane to {11■2} second-order pyramidal plane,then back to {10■1} first-order pyramidal plane.Under the condition where tensile twins are prevalent,{10■1} first-order and {11■2} second-order pyramidal dislocations are favorable to be activated.Both types of dislocations behave climb-like dissociations onto the basal plane,forming zigzag dislocations.

联合slipBERI与D-InSAR技术的青海省玛多县地震形变场提取与模拟

针对2021年5月22日青海玛多县Ms7.4地震震区形变信息、形变特征以及滑动断裂特性的提取与模拟等问题,获取了玛多县地震区的Sentinel-1A影像,采用双轨差分干涉法,并优化各项参数,提取出同震形变场,利用slipBERI(slip from bayesian regularized inversion)方法对断层的几何参数及形变场进行反演和模拟。结果表明:玛多地震同震形变场的形状近似于一个椭圆,断层整体呈西北-东南走向,其上部为沉降区,下部为隆升区,最大视线向(line of sight,LOS)形变分别为0.65 m和0.81 m。地震形变场的运动主要以东西方向的水平运动为主,并伴有明显的左旋走滑,断层上下方相对视线向运动可达1.50 m,表明此次地震的地表破裂有明显的错位移动。通过分析形变信息和地表破裂特征,可以判断该破裂带位于巴颜喀拉块体,为昆仑山口-江口断裂,反演结果与观测结果相符,这表明观测结果较可靠。

Underlying slip/twinning activities of Mg-xGd alloys investigated by modified lattice rotation analysis

The inconsistencies regarding the fundamental correlation between Gd content and slip(twinning)activities of Mg alloys appeal further investigations.However,the traditional slip dislocations analysis by TEM is time-consuming,and that by SEM/EBSD cannot recognize the partial slip modes.These urge a more efficient and comprehensive approach to easily distinguish all potential slip modes occurred concurrently in alloy matrix.Here we report a modified lattice rotation analysis that can distinguish all slip systems and provide statistical results for slip activities in Mg alloy matrix.Using this method,the high ductility of Mg-Gd alloy ascribed to the enhanced non-basal slips,cross-slip,and postponed twinning activities by Gd addition is quantitatively clarified.