Rock Damage Structure of the South Longmen-Shan Fault in the 2008 M8 Wenchuan Earthquake Viewed with Fault-Zone Trapped Waves and Scientific Drilling

This article is to review results from scientific drilling and fault-zone trapped waves （FZTWs） at the south Longman-Shan fault （LSF） zone that ruptured in the 2008 May 12 M8 Wenchuan earthquake in Sichuan,China.Immediately after the mainshock,two Wenchuan Fault Scientific Drilling （WFSD） boreholes were drilled at WFSD-1 and WFSD-2 sites approximately 400 m and 1 km west of the surface rupture along the Yinxiu-Beichuan fault （YBF）,the middle fault strand of the south LSF zone.Two boreholes met the principal slip of Wenchuan earthquake along the YBF at depths of 589-m and 1230-m,respectively.The slip is accompanied with a 100-200-m-wide zone consisting of fault gouge,breccia,cataclasite and fractures.Close to WFSD-1 site,the nearly-vertical slip of ～4.3-m with a 190-m wide zone of highly fractured rocks restricted to the hanging wall of the YBF was found at the ground surface after the Wenchuan earthquake.A dense linear seismic array was deployed across the surface rupture at this venue to record FZTWs generated by aftershocks.Observations and 3-D finite-difference simulations of FZTWs recorded at this cross-fault array and network stations close to the YBF show a distinct low-velocity zone composed by severely damaged rocks along the south LSF at seismogenic depths.The zone is several hundred meters wide along the principal slip,within which seismic velocities are reduced by ～30-55％ from wall-rock velocities and with the maximum velocity reduction in the ～200-m-wide rupture core zone at shallow depth.The FZTW-inferred geometry and physical properties of the south LSF rupture zone at shallow depth are in general consistent with the results from petrological and structural analyses of cores and well log at WFSD boreholes.We interpret this remarkable low-velocity zone as being a break-down zone during dynamic rupture in the 2008 M8 earthquake.We examined the FZTWS generated by similar earthquakes before and after the 2008 mainshock and observed that seismic velocities within fault core zone was reduced by ～10％ due to severe damage of fault rocks during the M8 mainshock.Scientific drilling and locations of aftershocks generating prominent FZTWs also indicate rupture bifurcation along the YBF and the Anxian-Guangxian fault （AGF）,two strands of the south LSF at shallow depth.A combination of seismic,petrologic and geologic study at the south LSF leads to further understand the relationship between the fault-zone structure and rupture dynamics,and the amplification of ground shaking strength along the low-velocity fault zone due to its waveguide effect.

Fault-zone trapped waves at Muyu in Wenchuan earthquake region

Trapped waves in the Qingchuan fault zone were observed at Muyu near the northeastern end of the fractured zone of the Wenchuan Ms8. 0 earthquake. The results indicate a fault-zone width of about 200 m and a great difference in physical property of the crust on different sides of the fault. The inferred location of crustal changes is consistent with land-form boundary on the surface

Spatial-temporal characterization of the San Andreas Fault by fault-zone trapped waves at seismic experiment site,Parkfield,California

In this article,we review our previous research for spatial and temporal characterizations of the San Andreas Fault(SAF)at Parkfield,using the fault-zone trapped wave(FZTW)since the middle 1980s.Parkfield,California has been taken as a scientific seismic experimental site in the USA since the 1970s,and the SAF is the target fault to investigate earthquake physics and forecasting.More than ten types of field experiments(including seismic,geophysical,geochemical,geodetic and so on)have been carried out at this experimental site since then.In the fall of 2003,a pair of scientific wells were drilled at the San Andreas Fault Observatory at Depth(SAFOD)site;the main-hole(MH)passed a~200-m-wide low-velocity zone(LVZ)with highly fractured rocks of the SAF at a depth of~3.2 km below the wellhead on the ground level(Hickman et al.,2005;Zoback,2007;Lockner et al.,2011).Borehole seismographs were installed in the SAFOD MH in 2004,which were located within the LVZ of the fault at~3-km depth to probe the internal structure and physical properties of the SAF.On September 282004,a M6 earthquake occurred~15 km southeast of the town of Parkfield.The data recorded in the field experiments before and after the 2004 M6 earthquake provided a unique opportunity to monitor the co-mainshock damage and post-seismic heal of the SAF associated with this strong earthquake.This retrospective review of the results from a sequence of our previous experiments at the Parkfield SAF,California,will be valuable for other researchers who are carrying out seismic experiments at the active faults to develop the community seismic wave velocity models,the fault models and the earthquake forecasting models in global seismogenic regions.

Exploration of fault-zone trapped waves at Pingtong Town,in Wenchuan earthquake region

Pingtong Town is located on the fractured zone of the Wenchuan 8.0 earthquake, and is seriously damaged by the earthquake. Our observation line is centered at an earthquake exploration trench across the fractured zone in the NW-SE direction, and is about 400 m long. The results reveal trapped waves in the rup- tured fault zone of the earthquake, and indicate a great difference in physical property between the media inside and outside the fault zone. The predominant frequency of the fault-zone trapped waves is about 3 -4 Hz. The wave amplitudes are larger near the exploration trench. The width of the fault zone in the crust at this location is estimated to be 200 m. In some records, the waveforms and the arrival times of S waves are quite different between the two sides of the trench. The place of change coincides with the boundary of uplift at the surface.

Study on rupture zone of the M=8.1 Kunlun Mountain earthquake using fault-zone trapped waves

The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral analyzing. The results show that: a) Both explosion and earthquake sources can excite fault-zone trapped waves, as long as they locate in or near the fault zone; b) Most energy of the fault-zone trapped waves concentrates in the fault zone and the amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault-zone trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or the lower the velocity is, the lower the dominant frequencies are; d) For fault zone trapped waves, there exist dispersions; e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced to be about 300 m and is greater than that on the surface.

GENERAL SOLUTION FOR INTERACTION OF SOLITARY WAVES INCLUDING HEAD-ON COLLISIONS

A general solution of the Boussinesq equation is presented which solves the problem of interaction of any number of right-going and left-going solitary waves.The solution relies on the exact solu- tion of Gardner,Greene,Kruskal,and Miura(1967),and has the same degree of accuracy as that solution, but has a wider scope of application.It is much simpler than,but as accurate as,Hirota's exact solu- tion(1973)of the Boussinesq equation,to which the present solution is compared for the simplest case of two solitary waves in head-on collision.

ON HEAD-ON COLLISION BETWEEN TWO GKDV SOLITARY WAVES IN A STRATIFIED FLUID

In this paper,using the reductive perturbation method combined with the PLK method and two-parameter expansions,we treat the problem of head-on collision between two solitary waves described by the generalized Korteweg-de Vries equation (the gKdV equation) and obtain its second-order approximate solution.The results show that after the collision,the gKdV solitary waves preserve their profiles and during the collision,the maximum amplitute is the linear superposition of two maximum amplitudes of the impinging solitary waves.

Head-on collision between two hydroelastic solitary waves with Plotnikov-Toland's plate model

Head-on collision between two hydroelastic solitary waves propagating at the surface of an incompressible and ideal fluid covered by a thin ice sheet is analytically studied by means of a singular perturbation method. The ice sheet is represented by the Plotnikov-Toland model with the help of the special Cosserat theory of hyperelastic shells and the Kirchhoff-Love plate theory,which yields the nonlinear and conservative expression for the bending forces. The shallow water assumption is taken for the fluid motion with the Boussinesq approximation. The resulting governing equations are solved asymptotically with the aid of the Poincaré-Lighthill-Kuo method,and the solutions up to the third order are explicitly presented. It is observed that solitary waves after collision do not change their shapes and amplitudes. The wave profile is symmetric before collision, and it becomes, after collision, unsymmetric and titled backward in the direction of wave propagation. The wave profile significantly reduces due to greater impacts of elastic plate and surface tension. A graphical comparison is presented with published results, and the graphical comparison between linear and nonlinear elastic plate models is also shown as a special case of our study.

HEAD-ON COLLISION BETWEEN TWO mKdV SOLITARY WAVES IN A TWO-LAYER FLUID SYSTEM

In this paper, based on the equations presented in [2], the head-on collision between two solitary waves described by the modified KdV equation (the mKdVequation, for short) is investigated by using the reductive perturbation method combined with the PLK method. These waves propagate at the interface of a two-fluid system, in which the density ratio of the two fluids equals the square of the depth ratio of the fluids. The second order perturbation solution is obtained. It is found that in the case of disregarding the nonuniform phase shift, the solitary waves preserve their original profiles after collision, which agrees with Fornberg and Whitham's numerical result of overtaking collision[6] whereas after considering the nonuniform phase shift, the wave profiles may deform after collision.

Effect of Ship Bow Overhang on Water Shipping for Ship Advancing in Regular Head Waves

这份报纸论述处理鞠躬的效果的试验性的调查的结果悬于发货的数量上的延期在在常规头波浪进展的轮船的情况下在前甲板上流水。执行这调查，一系列免费跑的测试在使用一艘多种用途的货物轮船的一个试验性的模型确定的常规波浪被进行装运水的数量。测试在五个弓上被执行悬于有波长和轮船的几联合的变体加速条件。装运水的数量被象波长，轮船速度，和鞠躬形状那样的一些参数以 overhang 扩展影响，这被观察。结果显示出 overhang 延期的重要影响，它与鞠躬闪光形状被联系，在水发货的出现上。这些结果包含联合到来的常规波浪和模型速度。

Heading control method and experiments for an unmanned wave glider

The control system designing of unmanned wave glider(UWG) is challenging since the control system is weak maneuvering, large time-lag and large disturbance, which is difficult to establish accurate mathematical model. The control system for the "Ocean Rambler" UWG is studied in this work. A heading control method based on S-surface controller is designed. For the "rudder zero drift" problem in trials, an improved S-surface control method based on rudder angle compensation is proposed, which can compensate the adverse effects from environmental forces and installation error. The tank test and sea trial results prove that the proposed control method has favorable control performance, and the feasibility and reliability of the designed control system are also verified.

Characteristics of head wave in multi-layered half-space

In this article, we analyze the dynamic characteristics of head wave in multi-layered half-space media models with high-velocity layer or low-velocity layer, and the model with a continuous transition-zone between the crust and the mantle by using synthetic seismogram. It is concluded that the dynamic characteristics of head wave are sensitive to the thickness and velocity of the high-velocity layer. There is obvious diffraction phenomenon of seismic wave if the thickness of high-velocity layer is very small compared with the characteristic wavelength. In this case, the high-velocity layer cannot shield the head wave propagating along the upper interface of the media below it, and the amplitude of this head wave is proportional to the thickness or the velocity of the high-velocity layer. When the thickness of high-velocity layer is nearly identical to the characteristic wavelength of seismic wave, the wave phases reflected from the bottom of the high-velocity layer and the head wave phase may have very close arrival and weaken each other because of destructive interference. As to low-velocity layer, the amplitude of the head wave is weak and decreases with the velocity of this layer. It is also found that if a continuous transition-zone between the crust and the mantle is introduced, we can get a strong apparent head wave phase in synthetic seismogram and the amplitude of this phase increases with the thickness or velocity gradient of the transition-zone.

Analytical Solution for the Transient Response of A Sloping Seabed Induced by A P-Wave Line Source

Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave line source embedded in the solid is presented.During the derivation,the wave fields in the fluid layer and the semi-infinite solid are firstly constructed by using the generalized ray method and the fluid-solid interface reflection and transmission coefficients.Then,the analytical solution in the transformed domain is obtained by superposing these wave fields,and the analytical solution in the time domain by applying the analytical inverse Laplace transform method.The the head wave generation conditions and arrival times at the fluid-solid interface are derived through this solution.Through the use of numerical examples,the analytical solution is proved right and the impacts of the sloping angle on the hydrodynamic pressure in the sea,the seismic wave propagation in the seabed,the head wave,and the Scholte wave at the seawater-seabed interface are also addressed.

Prospects and Current Studies on the Fault Zone Seismic Waves

Deep structure and material properties of faults can be understood by observing and simulating the particular phase in a fault fracture zone. This paper reviews the development of fault-zone seismic waves in the seismological domain. The present research status of fault-zone head wave and trapped wave are summarized systematically. Based on recent progress in this field,the paper discusses the prospect on the utilization of seismic wave in fault structure research.

三七活骨丸联合体外冲击波对气滞血瘀型早期股骨头缺血性坏死患者的影响

目的 观察三七活骨丸联合体外冲击波(ESW)对气滞血瘀型早期股骨头缺血性坏死的影响。方法 选取2021年4月至2022年10月黑龙江中医药大学附属第二医院收诊的72例气滞血瘀型早期股骨头缺血性坏死患者,采用随机数字表法将其分为对照组和观察组,各36例。对照组采用ESW治疗,观察组在对照组的基础上口服三七活骨丸,两组均治疗4周。观察治疗前及治疗2、4周后两组视觉模拟评分法(VAS)评分、髋关节Harris评分、中医证候评分,并进行疗效评价。比较两组治疗前后血清白细胞介素(IL)-1β、IL-6、肿瘤坏死因子-α(TNF-α)、骨保护素(OPG)水平。结果 对照组有4例患者在治疗期间服用其他药物,故剔除。观察组临床疗效优于对照组(P<0.05)。两组治疗2、4周后VAS、中医证候评分均低于治疗前,髋关节Harris评分高于治疗前,两组治疗4周后VAS、中医证候评分均低于治疗2周后,髋关节Harris评分高于治疗2周后(P<0.05)。治疗2、4周后,观察组髋关节Harris评分高于同期对照组,中医证候评分低于同期对照组(P<0.05)。治疗4周后,观察组VAS评分低于同期对照组(P<0.05)。治疗4周后,两组血清IL-1、IL-6、TNF-α水平低于治疗前,血清OPG水平高于治疗前,且观察组血清IL-1、IL-6、TNF-α水平低于对照组,血清OPG水平高于对照组(P<0.05)。结论 三七活骨丸联合ESW对于改善气滞血瘀型早期股骨头缺血性坏死患者的症状疗效良好,适合临床应用。

井下电力电缆故障定位研究

针对传统井下电力电缆故障定位方法依赖主观参数选择和抗噪性能较差,无法满足强噪声背景下井下电力电缆故障精确定位要求的问题,提出了一种基于樽海鞘群算法(SSA)优化变分模态分解(VMD)并结合改进型Teager能量算子(NTEO)的井下电力电缆故障定位方法。针对VMD在信号分解上存在的模态混叠、过分解和欠分解问题,采用SSA以模糊熵为适应度函数对VMD模态数K和惩罚因子α2个参数进行优化,得到更能反映故障特征信息的本征模态函数;采用NTEO对本征模态函数进行首波波头标定,得到首末两端的波头到达时刻,根据双端测距法得出故障位置。采用PSCAD/EMTDC进行井下电力电缆故障仿真,模拟具有强背景噪声的井下故障信号,结果表明:①在理想电流信号中加入9,12 dB噪声后,SSA-VMD的信噪比最低,皮尔逊相关系数最大,说明SSA-VMD在最大程度降噪的同时,能很好地保留信号的特征信息。②在不同过渡电阻下,SSA-VMD-NTEO的定位精度较高。③在不同故障相角下,SSA-VMD-NTEO在采样点上出现不同,但定位位置没有改变,依旧保持较高的定位精度。④在不同故障距离下,SSA-VMD-NTEO均能保证较高的定位精度。⑤在井下较大噪声和10 MHz采样频率下,SSA-VMD-NTEO较小波模极大值和VMD+NTEO 2种方法的定位精度具有明显优势。

400 km/h高铁隧道联通式缓冲结构对微气压波的影响

随着高速列车运行速度的提升,隧道口微气压波幅值剧增,强烈的爆破噪声同时影响着周边环境和附近居民的正常生活。本文研究由平行导坑与横通道组成的联通式缓冲结构对400 km/h高铁隧道微气压波的缓解作用。首先,进行400 km/h动模型试验,验证数值模拟方法的准确性;其次,基于RNG k-ε湍流模型和滑移网格技术分析联通式缓冲结构位置距隧道入口的距离D与联通式缓冲结构长度L对微气压波的影响。研究结果表明:随着D增加,微气压波的缓解率逐渐增大,在D=25 m时达到最优,微气压波幅值减少34.4%;随着L增加,微气压波幅值缓慢增加;当L=30 m时,隧道口20 m处的微气压波幅值为91 Pa,缓解率为37.1%。联通式缓冲结构与既有350 km/h高铁线路上的断面扩大开孔型缓冲结构组合,可将隧道口20 m处微气压波幅值减小至47.3 Pa,降幅达67.3%。联通式缓冲结构合理利用了修建隧道时遗留的平行导坑,可在保障施工成本几乎不变的前提下,显著缓解微气压波,保护隧道周边环境。

SV波斜入射时不同水体模拟方法下超高水头船闸地震反应分析

基于黏弹性人工边界的地震动斜入射方法模拟平面SV波不同角度入射情况,分别采用声固耦合法和附加质量法模拟闸室内水体,研究超高水头船闸闸室位移、应力和塑性损伤等地震反应,对比两种水体模拟方法计算结果的异同。结果表明:(1)整体上,两种方法计算得出的左、右闸墙地震反应结果随入射角度变化的规律基本一致;左闸墙受拉损伤的最大值均出现在入射角15°时,右闸墙受拉损伤的最大值均出现在入射角35°时;地震波入射角度对超高水头船闸动力响应影响较大,设计时应考虑地震波斜入射的影响。(2)当入射角较大时,采用声固耦合法计算的闸墙相对位移极值、主应力极值和受拉损伤结果偏保守的概率更大,对超高水头船闸结构设计来说更为安全。(3)建议两种计算方法相互参考和校核,推荐采用偏安全的结果进行超高水头船闸结构设计。

地震波斜入射时不同水深超高水头船闸地震反应分析

基于黏弹性边界的地震动斜入射方法模拟平面SV波和P波不同角度入射情况,采用声固耦合法模拟闸室内动水压力,研究超高水头船闸闸室在不同水深下闸顶位移、加速度和塑性损伤等地震反应。研究表明:地震波斜入射时,超高水头船闸的地震反应随水深变化的规律较垂直入射时明显不同,地震反应的程度一般较垂直入射时更大;相同水深条件下,闸顶水平相对位移峰值、水平加速度峰值多数情况下随入射角增大而增大。超高水头船闸闸室结构地震反应结果受水深变幅影响显著。一般闸墙相对高度为0.2附近的区域更易出现严重受拉损伤,相对水深为0.97时,闸墙临水侧达到严重破坏程度的受拉损伤范围最大。对综合考虑斜入射地震波和闸室内不同水深共同作用有一定的影响。