Through summarizing the prediction and judging situation of the earthquake tendency and earthquake key risk region,w hich w ere recorded in the research report of annual earthquake tendency consultation in Yunnan province from 1998 to 2012,w e induced the statistical and analytical results of the annual largest seismic activity strength,the corresponding situation of actual earthquakes in risk region and statistic analyzing result of prediction area of risk region in order to obtain the systematic know ledge of annual earthquake prediction in Yunnan region.

Based on water temperature digital data of wells in Yunnan province,the characteristics of coseismic changes of water temperature caused by Japan M9.0 and Wenchuan M8.0 earthquakes are analyzed.The results show that the characteristics are different in the different structure areas,and this may be related with the conditions,local geological structures and tectonic environments;the characteristics are similar in the same well for the different earthquakes,and they are not related with the earthquake direction and mechanism,but the temperature will be increased with the earthquake magnitudes or decreased with the epicentral distances.Under the dynamic loading of seismic wave,the accelerated convection and mixing of different temperature water in virtue of seismic wave caused water temperature changes,when the fluctuation of seismic wave gradually is quiet down,the water temperature near the probe begins to normal.

采用非均匀度方法,分别提取滇西北、滇中北、滇西南、滇东南和滇东北地区水氡观测资料的地震前兆群体异常.结果表明,该方法能满足水氡观测点所在地区成组中强地震的中、短临预报要求；且该方法能自动识别异常,排除人为主观影响,便于在其他震区进行预报效能检验.

Firstly,we introduce the development process of Yunnan Seismic Monitoring Network(YSMN).The running of Yunnan Regional Digital Seismic Network improves the monitoring ability of seismic activity,so we collect the double information of small earthquakes activities.In recent years,lots of important earthquake events are made to record by the running of digital seismic network in region and global,which provide a good future for the theoretical innovation and research on technology application in modern seismology.Accumulating massive observation data with high quality for a long time is the basis of studying the physical process of earthquake and internal earth structure.Finally,we analyze the time and spatial distribution characteristic of Yunnan M≥5.0 earthquakes activities since 20th century,and it is the important reference on analyzing the earthquake activity and strong earthquake risk in Yunnan.

Applying the Rayleigh Wave Tomography method to the processing of the continuous ambient data recorded by 46 broadband sub-stations of the Yunnan Seismological Network from November,2007 to May,2010,we obtain the background image of the phase velocity of the Rayleigh Wave with different periods in Yunnan area.Then,by removing the background phase velocity from the current phase velocity reconstructed by sliding time-window,we obtain the current velocity-perturbation images.Comparing the velocity-perturbation images with the distribution of moderate-strong earthquakes in Yunnan,we find that before moderate-strong earthquakes in the middle part of the Sichuan-Yunan Rhombic Block,Rayleigh-phase velocity increased significantly in the perturbation images of phase-velocity from 10s to 25s.

In this paper,the result of the study about the aftershock-swarm of the MS6.4 earthquake occurred on June 3,2007 in Ning'er,Yunnan Province was given and the existence of both shear-wave splitting and the extensive dilatancy anisotropy in the upper crust of Ning'er region were recognized.The fast shear wave has two preponderant polarization-directions—NW140°and NW150°,which agree with the regional principal compressive stress.The delay time of the shear wave dynamically responds to the variation of stress field and increases before strong aftershocks.

The medium-strong earthquakes(MS≥5.0) from 886 A.D.to 2009 in Yunnan are classified as 3 sequential types—mainshock-aftershock,multiple mainshock,and single shock.Then the spatial distribution of the 3 types of the earthquakes is studied.We find that the mainshock-aftershock sequence is in the majority in Yunnan,and the multiple mainshock sequence takes the second place.These two types of sequence are widely distributed in Yunnan,and the single shock sequence is mainly distributed in the areas such as Dongchuan,Yuxi,Yinjiang,and so on.In the sub-region of Northwest Yunnan,the proportion of the 3 types of sequence is in accordance with the one in the whole Yunnan area.The multiple mainshock(MS≥6.0) sequence in a special part(called Xiaodianxi) of the West Yunnan is dominant,and the mainshock-aftershock sequence(MS≥6.0) reaches 90% of the total in Southwest Yunnan and 83% in Southeast Yunnan.In Northeast Yunnan,the proportion of the multiple mainshock sequence equals with that of the single earthquake sequence,meanwhile,the proportion of single earthquake(5.0≤M≤5.9) sequence is the highest in Yunnan.

Doing the propagation path correction,site effect correction,and instrument response correction,etc.for the observational S-wave data,we obtained source spectra for the small-and moderate-earthquakes.Using Brune Source Model and by means of generalized inversion technique,we calculated the stress drop of 335 earthquakes(MS2.0～5.3)in Xiaojiang Fault Zone and its adjacent areas.The temporal and spatial features of the stress drop showed that earthquakes with higher stress drop(Δσ≥10.0 MPa)mainly distribute in Dongchuan,Qiaojia and the areas in the north of Qiaojia,Yuanmou,and Wuding region.The earthquakes with Δσ≥10.0 MPa account separately for 10.2%,10.9% and 1.6% of the total in the northern,middle and southern segment of the Xiaojiang Fault Zone.According to the seismicity in the Zone,we analyzed the strong earthquake risk in different segments of the Zone.On the basis of the precisely-relocated results from the simultaneous inversion of location and velocity structure,we also analyzed the variation of stress drop and focal depth,and the extension and distribution of the Zone in the deep Earth.

The principle of maximum entropy is used to study the relationship of earthquake magnitude and frequency and obtain the probability distribution function for magnitude under the condition of discrete magnitude.The results show:(1) the number of events equal to or greater than M should be determined by discrete summation rather than integration method,(2) when unlimited upper bound to magnitude is given,the b value is equal for the Gutenberg relation and the Richter relation.When an upper bound M_k is assumed,the Richter relation may not be a linear relationship.

In this paper, using focal mechanism solutions of moderate-strong earthquakes in Yunnan and its adjacent areas, and based on the statistical analysis of the parameters of focal mechanism solutions, we discussed in detail the earthquake fault types and the characteristics of the modern tectonic stress field in the Yunnan region. The results show that most moderate-strong earthquakes occurring in the Yunnan region are of the strike- slip type, amounting to 80% of the total. Normal faulting and normal with strike-slip and reverse and reverse with strike-slip earthquakes is almost equivalent in proportion, about 8 % each. The tectonic stress field of the Yunnan region is near-horizontal, and the dips of earthquake fault planes are large. There are three main dynamic sources acting on the Yunnan region： one is the NE, NNE and NNW-directed acting force from Myanmar, Laos and Vietnam; the second is the SE-SSE directed force from the Sichuan and Sichuan-Yunnan rhombus block and the third is the NW-NNW directed force from the South China block. These three acting forces have controlled the faulting behavior of the main faults and the characteristics of strong earthquake activity of Yunnan and its adjacent regions.

This paper collected seismic basic data before and afterthe 7.2 Myanmar earthquake and analyzed the geological structure background,focal mechanism,seismic intensity,seismogenic fault,regional stress field,source parameter,earthquake disaster and temporal and spatial distributions of the earthquake sequence in detail.In particular,strong earthquake trends in Yunnan region after the earthquake are discussed in detail.The knowledge gained has great practical significance in the future work for earthquake prediction.

The coda-wave attenuation factor Qc at the source region of Yao'an,Yunnan,MS6.0 earthquake in 2009 is estimated through single-scattering theory of coda wave on the basis of the digital waveform data of aftershock sequence recorded by Da'yao Station.When central frequency f=1.5 Hz,the coda attenuation ratio β(f) in Yao'an region ranges from-0.141 27 to-0.043 05,and the average is-0.074 60.The Qc-value of coda ranges from 33.3 to 99.8,and the average is 65.5.The relation between the Qc-value and frequency f is Qc(f)=45.3 f0.97.The coda factor is in direct proportion to magnitude,and in inverse proportion to frequency.In the first few days after the main shock,the Qc-value(1.5 Hz) of coda fluctuated obviously,it showed a tendency toward stabilization within the line of ±1.5 times of variance,and the strong aftershocks smaller than M5 will occur.The Yao'an region has the characteristics of active tectonic-movement,frequent seismic-activity,and low Qc-value.

Using the digital data from 2002 to 2010 recorded by Tengchong Seismic Station,we conducted a shear wave splitting and obtained the predominant direction of stress and the delay time of shear wave in different stages from 2002 to 2010 in Tengchong.Further,we found that the predominant polarization direction was in NE30°-55°,agreeing with the one of the regional principal compressive stress.The delay time of the shear wave provides useful information for the study of the regional stress field and the earthquakes prediction.

Based on seismic wave energy,using digital seismic waveform data,we present a quantitative predicttion index called seismic force scale σ value.We first introduced the method of calculating the σ value in detail,and then studied the variation of σ values in time and space before strong earthquakes.The results show:① The relationship between σ values and magnitude ML follows lgσ=0.98ML+6.93,and σ is a physical quantity that characterizes the average driving force of fault in earthquake source,with size between the earthquake frequency and energy;② In the Yunnan area,σ values appeared cyclic similar to the sine wave.Earthquake occurred in the vicinity of peak most occurred in the form of repeating,but mainly in the form of single earthquake around the trough.Taking the point 1.5 months from the bottom up in the σ value curve as forecast time,then the possibility of strong earthquakes is 78% within 3 months;③ High-value anomaly in σ values appeared 2~4 months before the main shock in the larger region.With the approach of the main shock,high σ values will move,concentrate and contract to the area of future main shock and the surrounding area,and σ values will be rapidly getting smaller a short period of time before the main shock(within 1 month),with obvious quiecence of seismicity.

We study the variation regularity of wave-velocity ratio in the 4th active period of strong earthquakes inYunnan,and discuss the relation between strong earthquake genesis and variation of wave velocity,medium-small earthquakes,and variation of focal depth.The result shows that wave-velocity ratio,focal depth and anomaly of M3-4.9 earthquakes appeared as early as 4 years before the M≥7.0 earthquakes.Most of them appeared about 2 years before the strong earthquakes,and anomaly of wave-velocity ratio and focal depth increased and gradually reduced about one year before the strong earthquakes.Corresponding to the beginning and the ending of the 4th active period.Wave-velocity ratio in Yunnan experienced the quasi-synchronous declining and rising.

On April 14,2010,an earthquake of magnitude 7.1 occurred in Yushu,Qinghai Province,it is the strongest earthquake that have ever taken place in this region.The earthquake is a strike-slip earthquake in the plateau,the Bayankala block south boundary.Seismogenic fault is Ganzi-Yushu-Fenghuoshan left-lateral and strike-slip fault,the earthquake major rupture to the southeast of the epicenter.The earthquake results from the Bayankala block and Qiangtang block east at different rates of movement,differential movement between the block boundary to accumulate stress to a certain extent to trigger fault rupture.Based on scaling law,fault rupture and stress parameters of the MS7.1 Yushu earthquake are estimated,resulting the seismic moment M0=1.78×1019 N·m,moment magnitue MW=6.8,area S=468 km2,maximum offset D=1.4 m,fault length L=37 km,the width W=12.6 km,shear stress τ0=16.8 MPa,stress drop Δσ=7.03 MPa.Analysis on historical earthquakes shows that Yushu magnitude 7.1 earthquake occurred in the world for more than magnitude 8 earthquake,in West China Triangle over magnitude 7.8 earthquake,north-south seismic zone earthquakes above magnitude 7 and the Bayankala block more than magnitude 7 earthquake in the context of intense activity.After the earthquake Yushu,Bayankala block and Qiangtang block and the Sichuan-Yunnan Rhombic block of Qinghai-Tibet Plateau future occurrence of more than magnitude 7 earthquake in more dangerous.

By power spectrum density estimation,we extract the fundamental-frequency,spheroidal,free oscillation(0S3～0S26)of the Earth excited by the M9.0 Sumatra-Andaman great earthquake on 26 December 2004 from the data of digital water-tube tiltmeters from Yunlong seismic station,Yongsheng seismic station,and Chuxiong seismic station in Yunnan Province without eliminating the Earth's tide.Comparing the extracted free oscillation with those observed by Benioff with the strainmeter Isabella and by Ness with the gravimeter Lacoste-Romberg and referring to the period of the extracted oscillation with that of the theoretical oscillation from the Preliminary Reference Earth Model(PREM),we find that they are in very good accordance with each other;the relative errors of 0S4 period,period 1,period 2,period 3 are greater than 0.3% while the relative errors of other periods are less than 3‰.This proves that extracting the free oscillation of the Earth from the data of digital water tube tiltmeter is a new approach.

We calculate the focal mechanisms of 14 earthquakes with M≥3.0 of the 2000 Yao'an MS6.5 earthquake sequence using the first motions of P,SV and SH waves and their amplitude ratios.The main seismogenic fault of the Yao'an earthquake trends in NW and has high dip angle,showing the feature of right lateral strike-slip under nearly horizontal main pressure stress.The focal faults of the Yao'an earthquake sequence mainly move by strike-slip with sporadic oblique-slip faulting under horizontal or nearly horizontal main pressure stress,and in 1-3 days after the mainshock,the fault slips by the way above mentioned,but in 3-30 days after the mainshock by the way of strike-slip.The azimuth of P-axis and T-axis changes with the direction of structural stress field regularly from consistently to inconsistently again to consistently.During the activity of strong aftershocks,the faults move mainly under horizontal or nearly horizontal main pressure stress,with certain oblique.The stress field shows obvious adjustment process after the mainshock.

基于最大熵原理,得到地震时间间隔和地震震级的概率分布函数.根据时间间隔分布,得到地震发震概率,当概率上升达到警界值时,可对云南5级以上中强地震做出预测.6个月以内中短期预测对应率为91%;3个月以内,短临期预测对应率为73%.根据震级分布,得到用最大熵原理求出的地震理论发生次数,理论发震次数与实际较为接近.用最大熵原理求出了云南不同地区不同震级档次5级以上中强地震的复发周期.分析认为,云南7级以上大震危险性在逐步逼近,西部危险性高于东部.

Based on the integrative interpretation of travel-time data and amplitude information obtained from the deep seismic sounding experiment on the Chuxiong-Luoping profile, eastern Yunnan province, carried out in January of 2005, we present a 2-D P wave velocity structure along the profile. The crustal structure shows remarkable contrasts between the two sides of the Xiaojiang fault zone, although the whole profile is situated within the Yangtze platform. The average P wave velocities of the crust on the west and east sides of the fault zone are 6.21 km/s and 6.32 km/s, respectively, and the crustal thicknesses are 41 km and 45 km, respectively. These results imply that the crust to the east of the Xiaojiang fault zone presents characteristics of crustal structure in a stable platform, while the crust to the west is complicated with a lower velocity zone in middle of the upper crust. The average velocity of 6.21 km/s is lower than the global continental crustal average (6.30 km/s), indicating that the region is tectonically active. According to the lateral variation of velocity and depth of interfaces (including the Moho), it is inferred that the Xiaojiang fault zone has cut through the whole crust. It is also deduced that existence of low velocity zone in middle of the upper crust is conducive to the south-southeastern sliding of the Sichuan-Yunnan (Chuan-Dian) rhombus block.