The Study on Seismicity and Relocation of the July 3,2015 Pishan MS6.5 Earthquake

The July 3,2015 Pishan M_S6. 5 earthquake occurred in the intersection area of the Tarim block and West Kunlun block where the moderate-strong earthquakes have become active in recent years. This paper has studied the seismicity parameters of the earthquake sequences such as the b-value in the Pishan region and its vicinity. In addition,we also relocated the aftershocks of the Pishan M_S6. 5 earthquake using the seismic phase report by the double-difference method. The temporal and spatial variation characteristics of the Pishan earthquake sequence in the rupture zone are analyzed. The study is of great significance in the seismic hazard assessment in this region.

Coseismic and postseismic slip ruptures for 2015Mw 6.4 Pishan earthquake constrained by static GPS solutions

On 3 July 2015, a Mw 6.4 earthquake occurred on a blind fault struck Pishan, Xinjiang,China. By combining Crustal Movement Observation Network of China（CMONOC） and other Static Global Positioning System（GPS） sites surrounding Pishan region, it provides a rare chance for us to constrain the slip rupture for such a moderate event. The maximum displacement is up to 12 cm, 2 cm for coseismic and postseismic deformation, respectively,and both the deformation patterns show a same direction moving northeastward. With rectangular dislocation model, a magnitude of Mw6.48, Mw6.3 is calculated based on coseismic, postseismic deformation respectively. Our result indicates the western Kunlun range is still moving toward Tarim Basin followed by an obvious postseismic slip associated with this earthquake. To determine a more reasonable model for postseismic deformation, a longer GPS dataset will be needed.

Analysis on Characteristics of the Hazards of the 2015 Pishan Ms 6.5 Earthquake in Xinjiang

The disaster area of the Pishan M_S6.5 earthquake in 2015 is located in the southern margin of the Tarim Basin,where the natural condition are harsh,and the economy is extremely backward.Moreover,because of a large number of residential housing with poor seismic performance in the disaster area,the damage and economic losses are serious.Since the most disaster area is located in the piedmont overflow,with poor site conditions such as shallow groundwater level and soil foundation,the magnifying effect of ground motion has a significant impact on the damage.In conclusion,we believe that investment in antiearthquake housing projects should be increased in post disaster reconstruction.Furthermore,for the north of the disaster area,with the dense population,poor conditions like soft soil foundation and poor engineering geological conditions,we recommend that in the future construction of anti-earthquake housing projects,more attention should be paid to strengthen the foundation treatment and precaution measures.

Temporal variation of gravity field prior to the Ludian Ms6.5 and Kangding Ms6.3 earthquakes

Using mobile gravity data from the central area of Sichuan and Yunnan Provinces, the relationship between gravity variation and earthquakes was studied based on the Ludian Ms6.5 earthquake that occurred on August 3rd, 2014, and the Kangding Ms6.3 earthquake that occurred on November 22 nd, 2014; the mechanism of gravity variation was also explored. The results are as follows：（1） Prior to both earthquakes, gravity variation exhibited similar characteristics as those observed before both the Tangshan and Wenchuan earthquakes, in which typical precursor anomalies were positive gravity variation near the epicenter and the occurrence of a high-gravity-gradient zone across the epicenter prior to the earthquake.（2） A relatively accurate prediction of the occurrence locations of the two earthquakes was made by the Gravity Network Center of China（GNCC） based on these precursor anomalies. In the gravity study report on the 2014 earthquake trends submitted at the end of 2013, the Daofu-Shimian section at the junction of the Xianshuihe and Longmenshan fault zones was noted as an earthquake-risk region with a predicted magnitude of 6.5, which covered the epicenter of the Kangding Ms6.3 earthquake. In another report on earthquake trends in southwestern China submitted in mid-2014, the Lianfeng, Zhaotong fault zone was also classified as an earthquake-risk region with a magnitude of 6.0, and the central area of this region basically overlapped with the epicenter of the Ludian Ms6.5 earthquake.（3） The gravity variation characteristics are reasonably consistent with crustal movements, and deep material migration is likely the primary cause of gravity variation.

The Change in Outgoing Long-wave Radiation before the Ludian Ms6.5 Earthquake Based on Tidal Force Niche Cycles

The cycle process of the tidal force niche for the Ludian M_S6.5 earthquake occurring in Ludian County, Yunnan Province, China on August 3, 2014 was calculated. The earthquake occurred near the middle point phase. It indicates that the type of seismogenic fault that the tide force acted on belongs to the thrust fault. According to the tidal niche cycle,the abnormal OLR( Outgoing Long-wave Radiation) change was analyzed based on NOAA satellite data around the whole land area of China before and after the earthquake.The result shows that the OLR changed evidently with tide force change. Temporally,the change went through the evolution process of initial OLR rise → strengthening → abnormal peaking → attenuation → returning to normal; and spatially,the abnormal area wound its way along the Zhaotong-Ludian fault and went through a scattered → conversion →scattered process. This process is similar to the change process of rock breaking under stress loading. The results indicate that the tidal force of a celestial body could trigger an earthquake when the tectonic stress reaches its critical breaking point and the OLR anomaly is proportional to the seismic tectonic stress change. It is of great use to combine OLR and tidal force in earthquake precursory observation.

地震亚失稳过程中前兆异常演化的综合解释——以2014年鲁甸6.5级地震为例

文中以2014年鲁甸6.5级地震为例,在亚失稳实验及理论指导下,基于震前地震活动及地球物理观测资料并结合地震成核数值模拟结果,综合分析前兆异常时空演化与亚失稳过程的关系,首次提供了一个可明确佐证亚失稳阶段震源区成核、震源区附近协同化过程持续加剧的典型震例和观测事实。研究结果显示,依据大区域强震活动及流动重力观测,可判定鲁甸地震前研究区已处于高应力状态。在高应力背景判定的基础上,依据地震活动及地球物理观测前兆异常,可粗略判定鲁甸地震亚失稳过程可能起始于震前7、8个月,最突出的现象或判定指标是由震中附近小地震活跃所表征的断层应力状态由积累为主向释放为主的转变,以及由定点地球物理观测异常数量显著增加所表征的断层运动协同化现象,从地震成核的角度与成核后期核心弱化区扩张过程有关。之后至主震发生,还有2个时间节点需要关注:一是震前4、5个月,定点地球物理观测异常空间分布范围自震中附近向外围的明显扩展,显示断层变形的加速协同化;二是震前2个月之后,震中附近小地震活动开始减弱、微震活动及定点地球物理异常出现向震中的迁移收缩,与地震成核过程核心弱化区扩展之后的收缩过程相关联。

2015年新疆皮山MS6.5地震震源机制及余震序列定位

利用新疆台网记录的波形数据,采用gCAP方法反演得到2015年7月3日新疆皮山M_S6.5地震的最佳双力偶节面解。其中,节面Ⅰ走向97°,倾角27°,滑动角51°;节面Ⅱ走向318°,倾角70°,滑动角107°;最佳矩心深度12km,矩震级M_W6.4;结合余震分布推断此次地震的发震断层为节面Ⅰ,主震破裂表现为逆冲型地震。同时,采用双差定位法对1014个地震进行相对定位,得到937个重定位地震事件,结果显示余震序列沿NWW向单侧扩展,展布长度约50km;震源深度主要分布在25km之上,且浅部地震较多;深度剖面显示在主震处断层面向SW倾斜,表现为上陡下缓的铲形逆冲断层特征,与主震破裂节面倾角具有较好的一致性。另外,余震序列空间分布展示出塔里木块体向西昆仑造山带下插入,且沿余震扩展的NWW方向,断层面倾角呈现逐渐增大的趋势,可能表明断层在向NWW破裂的过程中走滑分量逐渐增强。此次皮山地震是青藏高原N向挤压塔里木块体的结果,进一步印证了印度板块与欧亚板块的持续碰撞对青藏高原及周边地震活动具有强烈的影响。

2015年7月3日新疆皮山MS6.5地震序列震源机制解及发震构造分析

2015年7月3日09时07分,在新疆皮山县发生MS 6.5地震,震源深度约10 km,主震后一段时间内陆续发生一系列大小不等的余震。使用新疆测震台网原始波形数据和中国地震台网编目数据库震相数据,采用CAP方法反演皮山MS 6.5地震及MS 3.5以上余震序列震源机制解,得到震源机制解参数,其中:节面Ⅰ走向为136°,倾角为34°,滑动角为94°;节面Ⅱ走向为311°,倾角为56°,滑动角为87°;最佳震源深度为21.3 km;矩震级为MW 6.3。据皮山地区地质构造和余震序列展布,基本确定节面Ⅰ为发震断层面;通过震源球判定本次地震的断层活动主要表现为逆冲型特征,破裂优势方向SE,倾角以20°-40°居多,滑动角以70°-120°居多。

2015年7月3日皮山Ms6.5级地震热红外亮温异常分析

利用相对功率谱方法对风云卫星热红外亮温数据进行处理,发现皮山Ms6.5级地震前存在明显的前兆异常。异常区域时空演化特征为2015年6月21日阿尔金断裂带和西昆仑断裂带开始出现小幅度亮温功率谱增强现象,随后幅值和面积逐渐增大,持续至7月31日异常面积和幅度达到最大值,然后逐渐减弱,2015年8月28日后基本恢复正常。7月3日皮山Ms6.5级地震发生在异常持续增强的过程中,震中位于异常区域边缘的西昆仑断裂带。震中区域相对功率谱时序曲线与异常区域时间演化过程类似,地震发生在相对功率谱幅值增大的过程中。

新疆皮山MS6.5地震强震动观测记录初步分析

2015年7月3日新疆和田地区皮山县发生MS6.5地震,和田及喀什地区多处震感强烈。新疆强震台网共有39个台站获取到本次地震的加速度记录,记录到的最大峰值加速度为62.5 cm/s2。收集整理本次地震获取的强震记录,简要进行分析处理,初步判定本次地震对这39个强震台所在地区造成的破坏非常有限。

2022年7月2日皮山M_(S)5.1地震宏观异常调查与分析

以地震宏观异常现象的历史发展过程为出发点,具体描述和田地区皮山县震中周围动物震前、震后异常变化现象和特征。阐述了新疆和田地区皮山5.1级地震现场震中西南方向6~15 km村庄农户圈养的牛、羊等不同动物的反常现象,并针对在地震前后动物发生异常变化的18个调查点、98次异常进行详细统计。其中,皮山县乔达乡8个调查点7种动物宏观异常显著,异常数量总计46次;昆泉镇10个调查点4种动物宏观异常显著,异常数量总计32次。经统计,临近地震发生前24~36小时左右,狗、鸡、鸽、鸭反应异常显著,总宏观异常次数占比较高,动物主要表现为躁动不安、狂吠不止。由此分析得出:临震前,在不同时间段的11个调查点附近7种动物具有较明显的异常反应,从时间尺度上来看,离震中越近的地方,动物异常越早,异常动物数量、种类越多;反之越少。宏观异常现象具有向震中区域靠拢的趋势,空间分布较为集中。

Coseismic fault model of the 2017 M_(W)6.5 Jiuzhaigou earthquake and implications for the regional fault slip pattern

On August 8,2017,an M_(W)6.5 earthquake occurred in Jiuzhaigou County,Sichuan Province,China,on the eastern margin of the Qinghai-Tibet Plateau.This study investigates the coseismic deformation field and fault model with ascending and descending Sentinel-1 synthetic aperture radar(SAR)images,aftershock distribution,and elastic half-space dislocation model.The regional fault slip pattern is then quantita-tively examined using the boundary element method.The results show that the ascending and descending interferometric synthetic aperture radar(InSAR)coseismic deformation fields display an overall NNW-SSE trend,with more significant deformation on the southwest side of the fault.The coseismic fault geometry is divided into NW and SE sub-faults with strikes of 162.1°and 149.3°,respectively.The coseismic fault slip is dominated by a left-lateral strike-slip movement with an average rake of-2.31°,mainly occurring at a depth of 0-13.04 km with a shape of an approximately inverted triangle.The fault slip features two peak slip zones,with a maximum of 1.39 m.The total seismic moment is 6.34×10^(18) N·m(M_(W)6.47).The boundary element calculation quantitatively indicates that the regional fault slip pattern may be mainly attributable to the changing strike and dip.The strike changes from NNWeSSE to nearly NS direction,and the dip gradually decreases from the Jiuzhaigou earthquake fault in the north to the Huya fault in the south.With these characteristics,the Huya and the Jiuzhaigou earthquake faults form the eastern boundary of the Minshan uplift zone and accommodate the accumulated deformation.

A Preliminary Analysis of the Earthquake Disaster of Buildings during Two Destructive Earthquakes in Xinjiang

This paper introduces the characteristics of earthquake disasters in the 2013 Urumqi MS5. 1 and the 2015 Pishan MS6. 5 earthquakes,which are directly beneath the cities. Based on the discussion on regional tectonic background,site conditions,seismic fortification level of buildings,we preliminarily analyzed the causes of earthquake disaster for buildings caused by the two earthquakes. Finally,we give some advice on earthquake resistance for residential buildings and earthquake damage prevention in Xinjiang.

Spatial Correlation Anomalies of the Diurnal Variation of the Geomagnetic Vertical Component before the Yingjiang MS 6.1 and Ludian MS 6.5 Earthquakes

Significant anomalies were observed at the geomagnetic stations in the southwest region of China before the Yingjiang M_S6. 1 earthquake and the Ludian M_S6. 5 earthquake in 2014.We processed the geomagnetic vertical component diurnal variation data by the spatial correlation method. The results show that during the period from April 1 to May 20,2014,there existed quasi-synchronous decrease changes in the coefficient curves between the five geomagnetic stations of Guiyang,Hechi,Nanshan,Muli,Yongning and Xinyi and Hongshan stations. Furthermore,there was a high gradient zone in the normalized correlation coefficient contour map with background values removed. The epicenters of the Yingjiang M_S6. 1 earthquake and the Ludian M_S6. 5 earthquake are located in the gradient zone or near the gradient zone.

Ms 6.5 Earthquake Occurred in Ludian County of Yunnan Province,China,Although Forecast Issued before the Earthquake,Life Casualties and Property Losses were Still Caused Significant

1 Geography Location At 16：30 on August 3rd, 2014, Ludian County, Zhaotong City, Yunnan Province （27.1°N, 103.3°E） was hit by Ms 6.5 earthquake, with the maximum intensity is 9 and epicenter depth is around 12 km （Figs. 1 and 2）.

2022年3月17日皮山M_(S)5.2地震序列重定位研究

运用双差定位法对2022年3月17日新疆皮山M_(S)5.2地震及254个余震序列重新定位,结果显示:(1)皮山M_(S)5.2地震重定位结果为36.025°N,77.839°E,震源深度为17 km。(2)皮山地震的破裂沿断层向WS向迁移,破裂区能量释放较为充分,序列主要呈NE或SW向分布。(3)皮山M_(S)5.2地震主震发生在天神达坂断裂的北侧,其余震大多数分布在主震南侧。由定位结果判断发震构造是近NE-SW向的隐伏断层,断层破裂不均匀且深部破裂尺度较小。

2021年新疆皮山M_(S)5.4和叶城M_(S)5.4双震序列及青藏高原西北缘地震活动特征

利用新疆、西藏区域台网记录的P波和S波到时数据,对2009年1月至2021年9月期间的青藏高原西北缘的地震事件开展了精定位;利用新疆区域台网的地震波形数据,对2021年9月4日皮山M_(S)5.4地震和9月5日叶城M_(S)5.4双震序列中的12次M_(S)≥3.5地震事件开展了震源机制解反演;综合精定位与震源机制解结果,分析了皮山M_(S)5.4和叶城M_(S)5.4双震序列的震源特征;结合本文作者已取得的于田地区强震活动性研究结果,讨论了青藏高原西北缘两个强震区内(皮山—叶城地区与于田地区)的强震相关性.研究结果表明,(1)皮山M_(S)5.4和叶城M_(S)5.4双震序列的发震断层为NW向的泽普断裂带,两次M_(S)5.4地震的质心深度为17 km左右.(2)皮山M_(S)5.4和叶城M_(S)5.4地震之间伴有NE-SW向的次级隐伏拉张断层破裂.(3)2015年皮山M_(S)6.5地震序列呈现出NW向的单侧破裂,其余震区与此次皮山M_(S)5.4和叶城M_(S)5.4双震序列余震区没有重叠,两者属于不同的地震序列.(4)近年来,青藏高原西北缘"盆山交接地带"上的于田地区和皮山—叶城地区的强震活动性特征、发震构造模式及局部的构造动力源均不同.以东经80°为界,在其东侧的于田地区,大部分地震沿着NE向大型断裂带分布,少数地震沿着近乎NS向或NNE-SSW向的条带展布;断层错动方式以正断型或走滑型为主.在其西侧皮山—叶城地区,大部分地震活动沿着NW向分布,少量地震沿着NNE向的条带展布;断层错动方式以逆冲错动为主.

2022年3月17日皮山M_(S)5.2地震区域电磁异常综合分析

综合分析2022年3月17日皮山M_(S)5.2地震前震中附近存在的区域电磁异常特征。结果表明:①本次震中距离地磁低点位移预测线约280 km,且与优势发震时间接近,该异常对应本次地震;②本次地震虽然发生在地磁逐日比和地磁垂直强度极化预测区内,但震级偏小,且距离异常台站较远,异常不对应此次地震;③将地磁逐日比和低点位移进行综合分析有助于提高地震短期预测的准确性。

2014年8月3日云南鲁甸M_(s)6.5地震触发滑坡遥感解译研究

不同地貌环境下的同震触发滑坡类型会有巨大差异,确认同震滑坡类型对认识致灾特征有重要意义。本文以2014年8月3日云南鲁甸M_(S)6.5地震触发滑坡为例,利用多时相高分辨率卫星、航空遥感数据,结合遥感解译及野外调查方法,分析这次中强地震触发滑坡的主体类型。研究结果表明,①本次地震触发滑坡数量6209处,总解译面积9.72km^(2),其中10处面积大于70000m^(2)的滑坡造成震中区主要的堰塞湖堵江、生命线中断等严重灾情;②同震滑坡主体为基岩崩塌,物源区较小、流通区狭长,堆积区沿坡脚倒石堆,具有同震滑坡解译面积大而体积小的特征;③本次鲁甸M_(S)6.5地震触发滑坡具有中国西部高山峡谷地貌背景下的以基岩崩塌为主的特征。以上认识对该地区地震滑坡的定量研究有一定借鉴意义。

2015年7月3日皮山6.5级地震发震构造初步研究

基于新疆区域数字地震台网记录,采用CAP（Cut and Paste）方法反演了2015年7月3日皮山6.5级主震和部分MS3.6以上余震的震源机制解和震源深度;采用HypoDD方法重新定位了序列中ML2.5以上地震序列的震源位置,并利用小震分布和区域应力场拟合了可能存在的发震断层面参数.基于上述研究,综合分析了皮山6.5级地震序列的震源深度、震源机制和震源破裂面特征,探讨可能的发震构造.结果显示,利用CAP方法得到的最佳双力偶机制解节面I：走向280°/倾角60°/滑动角90°;节面II：走向100°/倾角30°/滑动角90°,矩心深度19km,表明该地震为一次逆冲型地震事件.大部分M_S3.6以上余震震源机制与主震具有一定的相似性.双差定位结果显示,M_L2.5以上的余震序列主要分布在主震的西南方向,深度主要分布在0~15km范围内,余震分布显示出与发震构造泽普隐伏断裂一致的倾向南西的特征.利用小震分布和区域应力场拟合得到发震断层参数为走向104°/倾角34°/滑动角94°,该结果与主震震源机制解中节面II的滑动角较为接近,绝大多数余震发生在断层面附近10km左右的区域.根据本研究得到的震源机制、精定位结果以及利用小震分布和区域应力场拟合得到的断层面的参数,结合震源区地质构造情况,初步给出了此次皮山6.5级地震的发震模式.