Determination of the fault plane using a single near-field seismic station with a finite-dimension source model

We explore the possibility of determining the actual fault plane of an earthquake from the inversion of near-source displacement seismograms of one station when a finite-dimension source is used instead of a point source model and when the complete displacement is taken into account, including near-field waves. Tests on synthetic seismograms and real data recorded at local distances show that this is possible even with a single, three-component station. A single accelerogram available for the Erzincan, Turkey, 1992 March 13, M _s = 6.8 earthquake is inverted and the solution found is compatible with other seismological studies and with the mechanism expected for the North Anatolian Fault.     

ON ENVIRONMENTAL CONDITIONS OF THE GENESIS OF TORNADO IN THE ZHUJIANG RIVER DELTA IN SPRING

Using observational data and the data of disastrous investigation of tornado in Zhujiang River Delta and Guangzhou's sounding from March to May of 1976-1983, the environmental conditions of genesis of tornado are analysed and compared with those of nontornadic local storm.It is found that the favorable conditions of genesis of tornado are lower pressure, unstable stratification and stronger wind in the deep layer of troposphere and higher temperature and humidity in low level, among which, lower pressure, more unstable stratification and layer wind are primary conditions for a severe local storm to possibly develop into a storm with accompanying tornado.The tornado mechanism is not related to vertical wind shear.     

A numerical prediction model of strong thermocline in the Bohai and the Huanghai Seas

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粘性土为主的地基强夯的时效性

根据浦东国际机场飞行区跑道地基强夯工程（三标）实测的不同时间的静力触探资料,讨论以粘性土为主的地基强夯强度增长的时效现象,得出：粘性土为主的地基,强夯的加艇具有滞后特性。     

On the reoccurrence of site specific response

The period and amplitude variations of local peaks in the Fourier amplitude spectra of free-field strong ground motion recorded at five stations in San Fernando Valley of metropolitan Los Angeles, California, are described, searching for peaks that reoccur during different earthquakes. The data suggest that some local peaks reoccur (about 50% of the time), during shaking by small local earthquakes (peak ground velocities, v_max<10–20 cm/s). During large strong motion amplitudes (v_max>20 cm/s), these peaks are shifted towards longer periods (by nonlinear response of soils) or disappear. The data also suggest that densification and settlement of soil, minutes and hours following the strong shaking may contribute towards fluctuations in the effective stiffness of the shallow surface layers.     

广西前汛期大涝年预报因子分析

通过对高原地面气温,热带海表面温度和南半球气旋资料的普查分析,经验性地挑选并提出１月份拉萨地面气温距平４月份赤道东西太平洋海表温度梯度,４月份赤道印度洋海表升温幅度,１月份南半球低纬气旋数等４种能提前１－２个月比较准确地预警广西前汛期大涝的因子,指出高原热状况,热带海洋行为,南半球低纬大气的斜压性是影响广西前汛期雨量的重要因素。     

川滇M≥63／4级强震前区域性中强震活动变化特征

研究了川滇22 次 M≥6 34 级地震前区域性中强震活动变化情况。验证了某些震兆特征的客观性和普遍性。本文研究结果给出, (1) 强震前区域性中强震活动相对活跃; (2) 震源附近可能发生多次5 ～6级地震; (3) 震中周围出现5 级以上地震组成的相对活动区或活动带; (4) 震源区周围相当范围内显示平静特征。追踪区域性中强震活动变化对于预测未来较大强震的危险性有实际意义。     

四川强震活动的时间间隔初析

本文将6 级以上强震分为连发与单发两类, 分别讨论了各自的间隔时间。有些强震发震时间间隔的部分规则性可以作为地震趋势研究的参考。     

Dynamic variation of ambient shear stress field before and after three strong earthquakes in Yunnan

IntroductionThecrustaltectonicmovementisacomplicatedevolutionprocesswithtimeandspace.Spatially,themovementofcrustaltectoniciscloselyrelatedtotheinter-movementandinteractionofmulti-leveledcrustalblocksinacertainregionandtheirborderfaults.Temporally,themovementiscloselyrelatedtothatofmulti-leveledcrustalblocksandtimesequencedevelopmentofinteraction.Anearthquakeoccurrenceistheresultofsuddenruptureofcrustmediaundertheactionoftectonicstressfield,isalsoacomplicatedprocessinnercrust.Duetotheobviousi…     

Direct Measurements of Deep Currents in the Northern Japan Sea

Long-term current measurements by means of subsurface moorings were made for the first time at seven sites in the Japan Basin, the northern part of the Japan Sea. The objective was to directly explore the velocity field in the highly homogeneous deep water mass (the Japan Sea Proper Water) that occupies depths below 500 m. On each mooring three current meters were equipped at an approximately equal distance below about 1000 m depth. Duration of the measurements was 1 to 3 years depending on specific site. This paper describes the basic data set from the moored measurements. It is found that the deep water of the Japan Basin is very energetic with eddies and vertically coherent currents of the order of 0.1 m/s. Surprisingly, the currents and eddies exhibit strong seasonal dependence even in the deepest layers of the Basin. The observed new current features are discussed in comparison with conventional deep circulation pictures derived from hydrographic data. This revised version was published online in August 2006 with corrections to the Cover Date.