Recent tectonic stress field and major earthquakes of the Bohai Sea basin

Introduction The present Bohai Sea is a half-closed shallow one in the continent, located at the northeast to North China, with an area about 7.3104 km2. Geologically, it is situated in the northern North China basin and of a short development history. Previous studies (WANG, LI, 1983; Institute of Oceanology, Chinese Academy of Sciences, 1985; HUANG, et al, 1993) show that the Fu-jian-Lingnan uplift in the East China Sea continental shelf sank gradually into the oceanic bottom, mak…     

RELATIONSHIP BETWEEN VELOCITY PROFILE AND DISTRIBUTION OF SEDIMENT CONCENTRATION

I. ON THE INFLUENCING FACTORS OF THE SEDIMENT~LADEN FLOW VELOCITY PROFILEThe influence of sediment on the water--now structures must be considered when thevelocity profile of the sediment--laden now (or turbid flow) is studied. widely usedparameters for reflecting thoses influences are the sediment concentrahon and theffichardson number, where Ri represents the variation of the concentration gradient.Generally, the vertical distributions of sediment concentration and th…     

中国辽南地区地壳与上地幔介质的横向不均匀性与海城7.3级地震

近几年来,在辽南地区开展深部地球物理探测的基础上,通过对深地震测深、大地电磁测深、重力、航磁、大地热流等综合地球物理资料对辽南地区地壳与上地幔介质进行不同物性的正、反演计算与研究,获得了辽南地区地壳与上地幔介质的速度结构、电性结构、密度结构和温度结构,揭示了该区介质的横向不均匀性及其重要特征.发现在海城地震区一带,存在壳内低速、高导、低密度、高热流等一系列重大地球物理异常,在空间上与震源区存在相当好的一致关系,对分析大震的震源物理过程提供了重要实际依据.     

A review of major progresses in mesoscale dynamic research in China since 1999

Mesoscale research conducted by Chinese meteorologists during the past four years is reviewed.Advances in theoretical studies include (a) mesoscale quasi-balanced and semi-balanced dynamics, derived through scale analysis and the perturbation method which are suitable for describing mesoscale vortices;(b) subcritical instability and vortex-sheet instability; (c) frontal adjustment mechanism and the effect of topography on frontgenesis; and (d) slantwise vorticity development theories, the slantwise vortex equation,and moist potential vorticity (MPV) anomalies with precipitation-related heat and mass sinks and MPV impermeability theorem. From the MPV conservation viewpoint, the transformation mechanism between different scale weather systems is analyzed. Based on the data analysis, a new dew-point front near the periphery of the West Pacific subtropical high is identified. In the light of MPV theory and Q-vector theory, some events associated with torrential rain systems and severe storms are analyzed and diagnosed.Progress in mesoscale numerical simulation has been made in the development of meso-α, meso-β vortices,meso-γ-scale downbursts and precipitation produced by deep convective systems with MM5 and other mesoscale models.     

Sequence of the Cenozoic Mammalian Faunas of the Linxia Basin in Gansu, China

In the Linxia Basin on the northeast margin of the Tibetan Plateau, the Cenozoic strata are very thick and well exposed. Abundant mammalian fossils are discovered in the deposits from the Late Oligocene to the Early Pleistocene. The Dzungariotherium fauna comes from the sandstones of the Jiaozigou Formation, including many representative Late Oligocene taxa. The Platybelodon fauna comes from the sandstones of the Dongxiang Formation and the conglomerates of the Laogou Formation, and its fossils are typical Middle Miocene forms, such as Hemicyon, Amphicyon, Platybelodon, Choerolophodon, Anchitherium, and Hispanotherium. The Hipparion fauna comes from the red clay of the Liushu and Hewangjia Formations, and its fossils can be distinctly divided into four levels, including three Late Miocene levels and one Early Pliocene level. In the Linxia Basin, the Hipparion fauna has the richest mammalian fossils. The Equus fauna comes from the Wucheng Loess, and it is slightly older than that of the classical Early Pl     

STUDY ON INTER-DECADAL AND INTER-ANNUAL VARIABILITY OF SST IN THE TROPICAL OCEANS*

Based on rotational empirical orthogonal function(REOF),max-entropy and Mexico-hat wavelet transform techniques,monthly SSTA of the tropical Pacific,Atlantic and Indian Oceans(32.5°S-32. 5°N) is investigated.It is shown that the inter-decadal variability and inter-annual variability take on global scale,and there exist their own significance areas.Moreover,through the total time series,the intensity of the variabilities is time-variable.And in fact,both the variabilities are usually coexistent.In significance areas of each of the variabilities,another variability is sometimes quite strong.     

Rupture directivity of the August 3rd, 2014 Ludian earthquake(Yunan,China)

An M6.5 earthquake occurred on August 3rd, 2014 in Ludian of Yunnan Province in China, causing severe casualty and economic loss. Local broadband waveform inversion with the CAP method demonstrates that the earthquake is a strike-slip event, with the strike along 70° and 160° for the two nodal planes respectively. However, the geological structure in the epicentral region is complicated with abundant active faults, and it is challenging to identify the seismogenic fault with the focal plane solutions due to nodal-plane ambiguity. We resolved the rupture directivity by measuring the difference between centroid location and hypocenter of the Ludian earthquake with the time shift from CAP inversion, and found that the nodal plane with the strike of 160° is the ruptured fault plane. Moreover, the rupture is found to propagate from northwest to southeast.     

天山造山带与准噶尔盆地壳幔过渡带 及其动力学含义

利用小波分析方法对天山造山带与准噶尔盆地壳幔过渡带的反射波进行处理,获得了来自各个爆炸点壳幔过渡带反射波走时曲线.计算结果表明,沙雅-布尔津地学断面的壳幔过渡带根据其特点可以分为三段塔里木盆地北缘、天山造山带与准噶尔盆地.塔里木盆地北缘的壳幔过渡带比较简单,主要由一级间断面构成;准噶尔盆地的壳幔过渡带也比较简单,除个别地段外皆以一级速度间断面过渡;天山造山带(尤其是北天山)的壳幔过渡带十分复杂,它由7~8个薄层叠合而成,层厚度2~3km不等,层速度高低相间,总厚度近20km.天山造山带与准噶尔盆地壳幔过渡带的结构特点及其两者之间的差异特征是天山造山带地球动力学"层间插入消减"模型建立的重要依据之一.     

单支迴折波走时曲线的解释及其在TI—59型计算机上的实现

在解释辽南地区的闾阳—海城—东沟深地震测深剖面资料过程中,遇到了很多的,带有重要浅层速度信息的单支迴折波走时曲线。本文针对资料解释过程中出现的具体问题,提出了单支迴折波走时曲线解释的原理与方法,并且在 TI—59型计算机上得以实现。给出了相应的流程框图及计算机源程序,并且把此方法用于间阳—海城—东沟深地震测深剖面的资料解释中。获得了重要的浅层信息,并为该剖面的二维计算机处理提供了重要的参数。