A seimic phase is often observed between P and S of continental earthquakes for epicentral distances less than 50km in regions with simple crustal structure. It is stronger on radial component than on vertical component, and its tangential amplitude is weak. The seismic phase is also less impulsive than P waves. From synthetic waveforms, we find that it is generated when S wave goes upward and is post-critically converted to P wave traveling along the free surface. It also may contain multiple conversion or reverberations of P wave near free surface. Because it results from coupling between S and P waves, we define this phase as sPL. For a half-space velocity model, sPL degenerates to surface P wave as defined by Aki and Richards, and it contains less high frequency energy due to its similar nature as head waves. But it may contain multiple reverberations of P wave near critical distance when there is substantial sub-surface velocity gradient. Waveform study shows that differential time between sPL and direct P is insensitive to epicentral distance, but increases almost linearly with the focal depth. It is used to determine the focal depths for a 2005 earthquake sequence in Jiujiang, China. Error analysis with synthetic waveforms indicates that 10% uncertainty in velocity structure will lead to depth error of about 2km or less. Focal depth from sPL has the advantage that it can be obtained from even only one seismic record in distance less than 50km and accurate epicentral distance is not required. It may help a lot to determine focal depth of small earthquakes with magnitude less than M3, thus will be helpful when only sparse seismic stations are available.

实际地震波形观测表明,对于大陆结构相对简单的地壳中的地震而言,有一震相出现在P 波和S波之间.一般在30~50 km附近发育得较好,其能量主要集中在径向分量,而垂向分量的振幅相对径向要小,切向分量上的振幅很弱,且波形以低频为主,通常没有P波尖锐.在利用FK方法计算合成地震图的基础上,发现该震相是由S波入射到自由地表形成水平传播的P波(文献称为surface P wave,自由地表P波)或者包括S波入射到地表后形成的多次P波或其散射震相.由于该震相是由S波和P波之间耦合而形成,本文将其定义为sPL(s coupled into P) 震相.理论波形研究表明,sPL相对直达P波的到时差对震中距离不敏感,而随着震源深度的增加几乎呈线性增加,因此可以很好的约束震源深度.本文以2005年江西九江地震为例,证实了sPL确定震源深度的可行性和可靠性.在观测到sPL震相的情况下,离震源50 km以内的一个三分量地震台站的波形就可以帮助获得可靠的震源深度,而不需要精确的震中距离.由于sPL震相出现距离较近,对于较小(三级以上)的地震也可以应用,因此在稀疏台网布局情形下sPL对于确定中小地震深度应该具有很好的应用意义.

From January 21 to April 16 of 1997, seven strong earthquakes took place in Jiashi region of Xinjiang, China. This Phenomenon was never happened in Chinese continent since earthquakes were able to be recorded by instruments. To investigate the deep structure environment of the Jiashi strong earthquake sequence, a portable broadband seismic array of 30 stations was set up in Jiashi region over about 11,000 km 2 . The portable array crossed the Tarim basin and the Tian Shan fold belt. The distance between stations is about 5-10 km. The frequency bandwidth of our observation system is 0.05--20 Hz. The 3--D S-wave velocity structure down to 100 km beneath the army was obtained by using the teleseismic receiver function migration and its nonlinear inversion techniques （Liu etc. 1996）. The following conclusions can be obtained from our observations: l) The Moho depth is about 4052 kin on the side of the Tarim basin and becomes 60-76 km deep on the side close to the Tien Shan. The crustal thickness beneath the fold belt nearby the south Tien Shan is much thicker than that of the Tarim basin and the obvious tectonic deformation exists in the crust. 2) The north boundary of the Tarim basin is clearly laterally inhomogeneous. The relationship of the contact deformation between Tarim and Tien Shan reveals the compressional movement to the NNW direction. The topography of the Moho discontinuity beneath our array has obvious correlation with the arctuate tectonics on the surface. The arctuate fold formation is closely related with the deep structure and the compression by the Tarim basin. 3) The Jiashi strong earthquake sequence mainly occurred over the gradient zone of the crust--mantle boundary. The genesis of the Jiashi earthquake sequence probably related to the activity of the conceal faults nearby the sources. This may result from the inhomogeneous deformation at the north boundary and the current tectonic movement of the Tarim basin. 4) The Jiashi strong earthquake sequence mainly occurred in the upper crust beneath the fold belt with a lower shear module. This could be a reason why the stress drop of these events is much smaller than common. All of these demonstrate that the Jiashi earthquake sequence genesis is related not only to the current tectonic movement of the Tarim basin, but also to the deep structure. This will need to be investigated further by the numerical stress modeling.

１９９７年１月２１日至４月１６日（北京时间）新疆伽师地区连续发生了７次６级以上 强烈地震．为了深入研究该强震群形成的构造背景，我们在伽师强震群区及其邻域大约 １１ ０００ｋｍ ２ 的范围内布设了由 ３０台宽频带数字地震仪组成的流动地震台阵，台站的间距约５－ １０ｋｍ．利用远震体波接收函数的叠加偏移分析及其非线性反演技术，研究了台阵下方０－ １００ｋｍ深度范围内地壳、上地幔的三维Ｓ波速度结构．结果表明：１)Ｍｏｈｏ界面的深度在塔里 木盆地一侧为４０—５２ｋｍ，而在靠近天山一侧的褶皱变形区为６０—７６ｋｍ，南天山山前折皱变形 区的地壳厚度明显增大，地壳内部产生了明显变形；２)塔里木盆地北缘存在明显的不均匀性， 塔里木盆地与天山之间的接触变形关系显示了塔里木盆地向北北西方向的挤压作用，台阵下 方壳幔界面的地形与地表的地貌特征有较好的相关性，山前弧形褶皱带的形成与地下深部结 构及挤压作用有关；３)伽师强震群分布在壳幔界面梯度带的上方，该震群的成因可能与震源 区附近的隐伏断裂活动有关；４)由于震源处于褶皱变形区的地壳上部，相应的剪切模量较小， 这可能是伽师强震群应力降明显偏低的...

The receiver functions with different azirnths at 10 CDSN stahons have been ob-taned from the broadband P wavefonns of 85 teededc events by using the mul-ti-channel maximal likelihood deconvoluhon meth0d' The lithosPheric S wave velodtystructures down to 100km deep bencath there stations are given by using the nonlinearcomplex driver function spectrum ratio inverson method.Our results show the fine lithospheric S veodty strructures under the CDSN stationsand the dear lateral variahons of the crustal theckness and lithosphtric velodty structuresunder the China continent. In particular, the crust under the Lahsa station is 66 km thick and the crust-mantle boundary is undear. The crust under the Sheshan station is 34 kmthick and the crust-mantle boundary has a sharp velodty contryst. The crustal tanessunder the CDSN stahons from our data is neariy consistent with the resu1tS by other meth-ods. Since the CDSN stahons cover the first-order fornic units of the China continent,otir rmlts provide a new evidence of the lateral inhomogendty of the Chna continentallithosphere.Keyweords:CDSN, Receiver function inverson, Lithosphere velodty structure

利用中国数字台网（CDSN）记录的85个远震事件的宽频带P波波形数据和分离接收函数的最大或然性反褶方法,获得了CDSN台网10个台站不同方位的岩石层接收函数.利用这些台站不同方位的平均接收函数和非线性接收函数反演方法,获得了上述各台站下方100km深度范围内的岩石层S波速度结构.结果表明CDSN台网各台站下方的地壳厚度和岩石层速度结构存在明显的差别.其中,拉萨台下方的地壳厚度为66kin,壳幔界面较模糊,而余山台下方的地壳厚度为34km,壳慢界面两侧速度反差明显.刮用本文方法估计的地壳厚度与已有的结果基本一致,由于CDSN台网覆盖了中国大陆的各主要构造单元,本文的结果为研究中国大陆的岩石层S波速度结构及其横向变化提供了新的证据.

Using the seismic waveforms recorded by the seismic array deployed in the southern section of the North-South seismic belt, the focal depths of 28 M-L >= 4. 0 aftershocks of the Lushan M(s)7. 0 earthquake are determined from the arrival-time differences between sPn and Pn phase. The Pn phase waves are picked by the waveform cross-correlation method, and the sPn phases are identified by using the sliding-window correlation method. The result shows that the focal depths are 10 similar to 20 km. From the NW-SE profiles perpendicular to the seismic belt, the focal depths became shallower from west to east with a dip about 39 degrees. The aftershocks show a linear characteristic in space, implying that they may be located in or near the faults relative to the main shock, and the fault dip of the main shock may be 39 degrees. According to the spatial distribution of aftershocks, we infer that the seismogenic fault of Lushan earthquake may be the blind thrust fault to the east of the seismic zone rather than the Shuangshi-Dachuan fault.

利用南北地震带南段密集流动地震台阵的观测数据，采用波形互相关方法拾取Pn波走时，应用滑动时窗相关法识别sPn震相，通过sPn与Pn震相之间的走时差测定了芦山地震序列中28个 M L 4.0级以上余震的震源深度.结果表明，震源深度集中在10~20 km范围内，垂直余震带的北西—南东向震源深度剖面揭示，余震分布表现出西深东浅的特点，倾角大约为39°.这些余震在空间上具有较好的线性分布特征，推测可能发生在与主震有关的破裂面上或邻近位置，由此推测主震的破裂面倾角大约为39°.根据余震的空间分布特征，认为芦山地震的发震断层并非双石—大川断裂，可能是其东侧的一条隐伏断层.

The source parameters of 9 strong events in the North China region have been determined with a joint moment tensor inversion of teleseismic and regional distance body waves （P, SH, Pnl）. Combined with the results of 7 events, which were obtained by other authors, the characteristics of fault plane solutions and focal depths of 16 strong earthquakes in North China have been analysed. The results are as follows: Most focal mechanisms for these events are predominant strike slip movement, both normal and reverse faulting occurred as well. The-focal depths for 16 events are in the midcrust about 10-25 km.

本文利用远震P波及SH波和区域地震P_(nl)波波形反演方法,测定了华北9次强震的断层面解、震源深度及地震矩.结合其他作者测定的7次地震的结果,分析了华北16次强震断层面解及华北地震震源深度特征.结果表明,华北多数强震为走滑型地震,也有个别正断层型及逆断层型地震;16次地震多数发生在地壳中部10—25km深度范围内.

We used broadband teleseismic data of Chifeng station to calculate the Receiver Functions, then obtained a velocity model with H-K stacking method in combination with CRUST2.0 and other previous work. With this velocity model and broadband records from 5 CDSN stations, we inverted focal mechanisms of Chifeng earthquake on August 16th, 2003 with the “Cut and Paste”(CAP) method. Then we confirmed focal depth and the source mechanisms by comparing synthetic body waves at teleseismic distance with broadband records of 9 IRIS stations. Our result shows that the best double couple solution of this M w 5.2 event is 315°, 64° and 19°for strike, dip and slip angles respectively, the second nodal plane solution is 216°,74°, and 152°. The focal depth is 25±2 km, suggesting that this quake occurred in the lower crust which is much deeper than most continental earthquakes. This lower crust earthquake requires that the rock should be colder than expected. We proposed generation mechanism of this deep earthquake and its implications in rock strength and thermal state.

利用宽频带远震数字地震记录，计算赤峰台下方接收函数，得到了MOHO面深度为34~35 km，并结合CRUST2.0模型等前人工作成果得到了赤峰地区的速度结构.我们以此速度结构作为模型，利用中国国家地震台网（CDSN）5个台站的宽频带地震数据，采用CAP方法反演2003年8月16日赤峰地震震源机制解并初步确定震源深度；再利用IRIS 9个台站远震体波数据，通过对比理论计算和观测记录的方法进一步精确确定震源深度并验证反演得到的机制解，得出此次地震矩震级为5.2，震源机制解为：节面I：315°/64°/19°，节面II：216°/74°/152°，震源深度为25±2 km，已深达下地壳.本文初步讨论了这样的发震深度所对应的可能发震机理和岩石物理特征，认为赤峰地区的下地壳处于相对低温的状态.

On January 19, 2011, a magnitude M(L)4.8 earthquake occurred in the region between Anqing and Huaining in Anhui province, which is a relatively strong earthquake and can be felt in Anqing and surrounding areas. To better understand the seismotectonics of this event, we try to relocate it and further study its focal mechanism based on the local broadband waveform data of available stations in Anhui and adjacent province regional seismic networks. In this work, the earthquake was relocated with absolute relocating method Hypo2000 at first, and then the focal mechanism and focal depth were determined by the "Cut and Paste" (CAP) method. In order to better constrain the focal depth, we further refined it with depth phases such as P, sP, pP and sPmP. Finally, the results of focal mechanism and focal depth were confirmed by comparing the observed records and the synthetic waveforms which were computed by F-K method. The results indicate that the Anqing earthquake is a thrust event with a small part of strike-slip component. The best double couple solution is 131 degrees, 30 degrees and 29 degrees for strike, dip and slip angles respectively for one nodal plane, and 15 degrees, 75 degrees and 116 degrees for another. The moment magnitude is 4. 3, and the estimated focal depth is 4 similar to 5 km, which suggests that: this event is a shallow earthquake and capable of heavy hazard to the surrounding areas. According to the epicenter and the focal mechanism, Anqing earthquake likely occurred on the Susong-Zongyang Fault.

2011年1月19日在安徽省安庆市辖区与怀宁县交界处发生了 M L 4.8级地震,引起安庆市及周边地区强烈的震感.为了更好地认识这次地震的发震构造,我们利用安徽省及临近几个省份区域台网的近震波形资料,首先通过hypo2000绝对定位得到震中位置;然后采用CAP方法反演了该地震的震源机制解和震源深度,并在此基础上结合P、sP、pP和sPmP等深度震相对震源深度进行了精确确定;最后,将反演得到的结果作为已知输入,利用F-K方法计算理论地震图,并与观测记录进行对比,以验证结果的可靠性.反演结果显示,这次安庆地震是一个带少量走滑分量的逆冲型地震,地震矩震级为 M W =4.3,最佳双力偶解为节面Ⅰ走向131°,倾角30°,滑动角29°;节面Ⅱ走向15°,倾角75°,滑动角116°,最佳震源深度为4~5 km,属于浅源地震.从震中和震源机制解来看,安庆地震极有可能发生在宿松-枞阳断裂上.

Gaoyou and Baoying M 4.9 earthquake occurred at 20:11 on July 20, 2012,It is the biggest earthquake of nearly 22 years on land in Jiangsu area.This article use the F-K method to simulate sPL depth phases obtained synthetic seismogram at different depths model,then fitted compare with the actually observed waveform in the radial direction (R)、 tangential (T) and vertical direction (Z),the focal depth is finally determined.According to the range of advantage epicentral distance of sPL phases is 30~50 km,to filter out Baoying(BY)、Yancheng station(YC) of waveform recorded high SNR to calculate From Jiangsu digital seismic network,the calculated result shows：the fitting results of synthetic seismogram and observed waveform at Baoying and Yancheng station was the closest when focal depth model were 11 km and 10 km. This result was Consistent with focal depth about 10.2 km, to be obtained from the double difference method that be used of combined with cross-correlation waveform,Preliminary indication of using sPL phase to determine the focal depth is reliable in the central region of Jiangsu of covering thickness.

2012年7月20日20时11分在江苏高邮与宝应交界发生了 M 4.9级地震，是江苏地区陆地上近22年来的最大地震.本文是运用频率-波速（F-K）方法，来模拟得到深度震相sPL在不同深度模型下的理论地震图，然后在径向（R）、切向（T）和垂直向（Z）上与实际观测波形进行拟合比较，来最终确定出震源深度.根据sPL震相的优势震中距范围30～50 km， 从江苏省数字地震台网中，筛选出波形记录质量信噪比高的宝应台（BY）、盐城台（YC）来进行计算，计算结果显示：宝应台和盐城台在震源深度模型分别为11 km和10 km时，理论地震图和实际观测波形的拟合结果最为接近.这一结果与利用结合波形互相关的双差定位法获得的震源深度，约10.2 km基本一致，初步表明在覆盖层厚的江苏中部地区，利用sPL震相来测定震源深度是可靠的.

对中国大陆地震的震源深度资料作了系统研究. 震源深度的研究, 对于探索地震孕育和发生的深部环境, 地震能量集结、释放的活动构造背景, 以及地壳内部构造变形及其力学属性等都有非常重要的意义. 以1970年1月~2000年5月期间中国大陆M L ≥2.0级并给出深度的31282次1和2类精度的浅源地震为基础, 研究了深度分布特征, 并采用网格滑动平均方法, 统计了网格内地震的平均深度. 结果表明, 中国大陆平均深度为(16±7)km, 东部地区为(13±6)km, 西部为(18±8)km, 东部比西部平均偏浅5 km. 我国大陆地震深度最大的地区是新疆西南部地区, 即塔里木地块的西端和西南缘. 震源深度与构造分区的关系密切, 青藏活动地块震源深度平均为(33±12) km. 新疆活动地块为(21±10) km, 华北为(14±7) km; 东北为(11±5) km; 华南为(10±4) km. 完整地块边界上的地震较深, 其中最明显的是塔里木盆地的西南缘、北缘; 准噶尔盆地的南边缘, 阿拉善地块的南边缘; 鄂尔多斯地块的东、西两侧以及四川盆地的西边缘. 在新生性的破裂带上地震偏浅, 如滇西南地震带及张渤地震带. 另外, 还根据我国震源深度分布特征, 讨论了壳幔(主要是地壳)力学行为、变形属性和破坏方式.

利用四川区域数字地震台网记录,采用滑动时窗相关法识别sPn震相,测定了四川攀枝花2008年8月31日Ms 5.6地震的震源深度.研究结果显示,震源深度为17 km,表明震源位于中上地壳.元谋-绿汁江断裂带上中强地震分布与断裂走向吻合,震源机制解以走滑为主,这些表明此断裂近乎直立.结合此次地震的震源深度,我们推测此断裂可能达到20 km深.

As an effective focal mechanism inversion method for regional earthquakes, CAP (Cut and Paste) is widely used in China in recent years. Its quality and error level need to be evaluated for such solutions are increasingly retrieved. On the other hand, when using the CAP method, those phases which fitted well are usually chosen for inversion, and the other phases which are thought 'bad’ or fitted not so good are ignored. It has been found that different station combinations will lead to varied results with unneglectable discrepancies. Objectively speaking, in a scientific perspective, this artificially selected process will increase uncertainties in final inversion results, especially under the present instrument status in China. Furthermore, because the grid search scheme used in the CAP method which is not evenly distributed on focal sphere, we can not give a convincing proof to illustrate that whether the cause of badly-fitted waveforms comes from data error or from un-sufficient searched solutions.#br#Two earthquakes of M 4.6 and M 4.3 occurred in Shandong Peninsula on 23 November 2013 and 7 January 2014, respectively. The former is the largest event in the Shandong area since 1995. For convenience, we label the former event as the Laizhou earthquake, and the latter as the Rushan earthquake, according to their epicenters. Taking these two events for example, this paper discusses error estimation for focal mechanism inversion using the CAP method. The paper also presents an uncertainty analysis process for the inversion results.#br#Briefly, a bootstrap technique is adopted, waveforms are randomly sampled with equal probability from origin dataset, and then used as data for a repeating inversion procedure. After a large number of inversions, e.g., 1000 times, we finally get bootstrap results consisting of 1000 focal mechanisms.#br#Based on these focal mechanisms, we conduct the following work. (1) We employ a PSO (particle swarm optimization) algorithm to search a solution, of which the Kagan angle is minimal to all the double couple models, and use its standard deviation as the inversion results uncertainty range. The uncertainty of solutions for the Laizhou event is ±23.7°; for Rushan event, is ±6.4°. These two solutions can be evaluated as ‘A’ level according to the Hardebeck's indicator of mechanisms quality.#br#(2) A clustering analysis is used for bootstrap results. For the Rushan event, the clustering center is coincident to the PSO optimized solution; for the Laizhou event, several centers are found in clustering, despite isolate solutions. There are two clustering centers, of which the corresponding data proportion is about 98.7 percent.#br#(3) Projecting P and T axes of bootstrap results onto a focal sphere, calculating its probability density, we get the probability density distribution of focal mechanisms on the focal sphere. Then we can give the confidence interval on different levels for mechanism solutions.#br#The method demonstrated in this paper is not confined to achieving more accurate focal mechanism and obtaining rational inversion error, while it can also be used to exclude isolate and incorrect solutions effectively, and avoid the effect of data from stations with larger disturbances. Therefore, this method can be used to invert focal mechanisms automatically immediately after moderate earthquakes occur. Sustaining by powerful computational capabilities, we can get more accurate and reliable focal mechanism results without manual work.

利用区域波形数据使用CAP方法反演中强地震的震源机制正逐渐得到广泛应用.本文以胶东半岛近期发生的两次显著中等地震为例,讨论了使用CAP方法反演震源机制时的误差估计,展示了反演结果的不确定性分析过程.2013年11月23日和2014年1月7日在山东莱州和乳山分别发生了 M 4.6和 M 4.3级中等地震,两次事件均造成了较大影响.我们基于CAP方法,使用自助抽样(bootstrap)技术多次重复反演过程,得到大样本量的震源机制解数据;基于这些数据,使用粒子群算法和聚类分析技术给出了优化解,估计了震源机制解的误差范围,并利用震源机制解的 P、T 轴给出了震源球上的概率密度分布.

The seismological observation system in China has experienced rapid development over the Tenth Five-year Plan period. The technical system construction of Data Backup Centre for China Seismograph Network is one of the most important parts of China Digital Seismological Observation Network program, which has been completed in Institute of Geophysics, China Earthquake Administration at the end of 2007. The data centre is capable of receiving near real-time continuous waveform data from more than 1000 permanent seismic stations, and also manipulating that data, including data quality control, data format converting, event data extraction by user order and data download service via internet. By now, we have supplied about 70 TB waveform data to over 70 researches of over 10 academic institutes and universities, especially the studies concerned with the Wenchuan great earthquake. The paper will give a brief introduction to the technical system construction, rapid response of data service to the Wenchuan earthquake studies, construction of automatic event-extracted system for rapid response of large earthquake in near real-time and data support to scientific researches.

“十五”期间中国地震观测系统得到了迅速的发展, 中国地震局地球物理研究所于2007年底完成“中国数字地震观测网络”项目“国家数字测震台网数据备份中心”技术系统的建设.该数据备份中心可以准实时地接收并存储全国1000多个固定地震台站的信号，具备海量数据校验、数据格式转换、以用户定制方式截取地震事件波形数据和数据网络下载的功能.到目前为止，已累计为国内10多个科研单位开展的70多项研究提供了近70TB海量波形数据的服务，特别在快速开展的汶川特大地震震后相关研究中提供了重要的数据支撑和保障作用.本文介绍了“国家数字测震台网数据备份中心”技术系统建设、汶川特大地震数据服务快速响应、大地震快速响应波形数据自动截取系统建设，以及对地震学及相关科学研究的数据支持情况.