Modelling the Quaternary evolution of shore platforms and erosional continental shelves     

A. S. Trenhaile 《地球表面变化过程与地形》2001,26(10):1103-1128

A mathematical model was used to investigate the effect of glacially induced fluctuations in sea level on the evolution of wave‐cut shore platforms and erosional continental shelves during the Quaternary. The model used two deep‐water wave sets, which were used to calculate breaker height and depth, and the force of the waves at the waterline, according to the width and bottom roughness of the surf zone and the gradient of the submarine slope. The model also incorporated an erosional threshold related to the strength of the rocks, the number of hours each year in which the water level is at each intertidal elevation and the amount and persistence of the debris at the cliff foot. Most runs were made using a sea level model that consisted of 26 glacial cycles from 2 million to 0·9 million years ago, and nine, of approximately twice the amplitude and wavelength, in the last 0·9 million years. The model emphasized the dynamic association between the contemporary intertidal platform and the continental shelf. Both surfaces trend towards a state of static equilibrium under oscillating sea level conditions, when attenuated waves are unable to continue eroding the rock. If there has not been enough time to reduce the gradient of the shallower portions of the continental shelf, however, intertidal shore platforms can be in a temporary, though possibly long‐lasting, state of dynamic equilibrium. The model suggests that most platforms are, at least in part, inherited from one, or in many cases more, interglacial stages when sea level was similar to today's. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

菏泽5.9级地震前后三项地震活动性参数的空间动态演化     

王红卫  刁守中 《华北地震科学》1994,12(1):54-61

用地震活动性参数（地震频度Ｎ，地震能量Ｅ和地震ｂ值）的二维空间等值线计算机扫描技术，系统地追踪了１９８３年菏泽５．９级地震前后三项地震活动性参数的空间动态演化情况。结果表明，菏泽５．９级地震前１－４年，河北平原断陷南部地区特别是其东界聊考断裂带地震活动异常增强，地震频度增高，地震能量释放加速而地震ｂ值降低；地震活动增强区的长度约２００余公里，未来主震发生于地震活动增强区的边缘；震后约一年左右震中周  相似文献   

Rates of tafoni weathering on uplifted shore platforms in Nojima-Zaki,Boso Peninsula,Japan     

Yukinori Matsukura  Norikazu Matsuoka 《地球表面变化过程与地形》1991,16(1):51-56

Many tafoni occur on the faces of marine cliffs on three uplifted shore platforms with different altitudes and with known ages of emergence. The mean value of the ten largest depths of tafoni, D (cm), was obtained and the period of their formation, t (years), was estimated. The relationship between the two variables was found to be D = 20·3 × (1?e^?0.005t).  相似文献   

On the crust structure near focus and the far-field body wave synthetic seismograms     

Dong-Sheng Li  Hui-Lan Zhou 《地震学报(英文版)》1993,6(4):823-831

In this paper we discuss two types of crust models with abnormal density, velocity of wave and certain geometrical structures. The far-field synthetic seismograms of P and SH wave are calculated by the far-field vertical displacement formulas of P and SH waves with the double couple point source and the formulas of reflection coefficient, radiation pattern and travelling time difference derived from the models suggested in the paper. It is shown by the results that the effect of special crust structures near focus on the far-field seismograms can be ignored if the densities and wave velocity of the special structure are less than average those of the crust (model I). However the effect should be noticed if the densities and wave velosities of the structure are large than average those of the crust (modelI). The effect of the special crust structure on the far-field seismograms has not been studied further before. Seismic records of the Haicheng earthquake and the crust structure in Haicheng region are studied by the calculation method in the paper. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 1993.  相似文献   

泰安地区近震波速及地壳厚度的测定     

刘洪瑞  肖凤莲 《地震地磁观测与研究》1992,13(4):25-29

本文第一部分选取泰安台473型地震仪1985—1990年记录的70个地震资料,通过计算,得到泰安台附近的地壳厚度为H=36.5km,直达波的平均传播速度:V_P=6.18km/s、V_s=3.55km/s;反射波的传播速度:V_(P11)=6.45km/s、V_(S11)=3.79km/s;绕射波的传播速度:V_(Pn)=7.95km/s;平均虚波速度:V_φ=8.34km/s;平均波速比K=1.74。第二部分选取了泰安台基式地震仪有SP′震相记录的地震21个,求出了泰安台附近的地壳厚度为37km,并分析了SP′震相在泰安台的记录特征,初步得到SP′震相可观测范围为25°—60°。  相似文献   

Variations of the geomagnetic field and the geomagnetic effects of three earthquakes ( M _s>5.0) in Jiangsu Province, China     

Chunyi Peng  Xiaoyong Zhang  Xinping Yang  Guoming Xu 《地震学报(英文版)》1992,5(1):145-152

Since 1979 the repeated observations and experiments of geomagnetic total intensity and vertical component have been carried out for ten years in the geomagetic network which is located in Jiangsu Province, China. Three earthquakes aboveM _s 5.0 occurred during the decade, and some seismomagnetic effects were observed. The observation results show that the anomalies of the vertical geomagnetic component can’t be observed untill some months before the earthquake (M _s>5.0) in this area. In this paper it is suggested that a densely distributed network for continuous observation of geomagnetic vertical component may catch seismomagnetic anomalies and thus improve earthquake prediction in the light of the geomagnetic measurements of the mid — or — low latitude locations. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 80–87, 1991. This study is sponsored by the Chinese Joint Seismological Science Foundation.  相似文献   

地物反射光谱对MODIS近红外波段水汽反演影响的模拟分析   总被引：14，自引：1，他引：14  

王伟民  孙晓敏  张仁华  唐新斋  朱治林 《遥感学报》2005,9(1):8-15

在近红外辐射传输方程的基础上,利用近红外波段水汽的不同吸收属性,在MODTRAN的模拟下,深入分析了基于MODIS近红外数据的可降水汽反演算法,并着重讨论了地物反射光谱非线性在可降水汽反演中的影响。研究结果显示,当波段间反射率之比不等于1时,MODIS近红外波段反演水汽将存在较大偏差。同时,在地物光谱库基础上,计算了不同地物反射率比值,其分布表明,大部分地物波段反射率比值不等于1。研究表明,应用现有MODIS近红外波段水汽反演算法,如果不考虑地表反射率光谱变化的影响,由地表反射光谱造成的误差最大约为反射率比值与1偏差的15倍,同时,这一误差还与大气波段透过率之比有关。  相似文献   

Simulationsof Aerosol Optical Properties to Top of Atmospheric Reflected Sunlight in the Near Infrared CO2 Weak Absorption Band          下载免费PDF全文

YANG Dong-Xu  LIU Yi  CAI Zhao-Nan 《大气和海洋科学快报》2013,6(1):60-64

Over the Asian continent,high aerosol loading is critical to ensure the high accuracy of CO₂ retrieval in the near infrared absorption band.Simulations were performed to explore the effect of light path modification by aerosol son the atmospheric CO₂ near infrared band(6140-6270 cm^-1).The Vector LInearized Discrete Ordinate Radiative Transfer（VLIDORT） model and the Line-By-Line Radiative Transfer Model（LBLRTM） were used for forward calculations.The U.S.standard atmosphere was used for atmospheric profiles.The results indicate that the aerosols caused similar effects to increases in CO₂ in the planetary boundary layer and became more significant with aerosol layer rising while aerosol optical depth was 0.1.This effect will cause an over estimation of the CO₂ mixing ratio in the retrieval process and an under estimation in the aerosol layer.The results also indicate that the effect of urban and industrial aerosols is smaller than that of non-absorbing and dust aerosols because of the nearly constant absorption properties in the near infrared band.  相似文献   

PARASOL/POLDER3卫星数据的海洋上空云检测     

陈震霆  孙晓兵  乔延利 《遥感学报》2018,22(6):996-1004

在卫星海洋遥感中,云作为海气耦合系统最重要的调节器之一,其检测结果对海洋上空云微物理特性的反演精度有较大影响。因此,快速而准确识别海洋上空的云像元是卫星遥感数据处理过程中首要解决的关键问题。以PARASOL (Polarization and Anisotropy of Reflectances for Atmospheric Sciences coupled with Observations from a Lidar)卫星搭载的POLDER3载荷遥感数据为研究对象,提出一种改进的海洋上空云检测方法。首先剔除海洋耀光;接着利用有云与晴空区近红外反射率差异检验识别有云像元,并利用偏振反射率检验进一步识别低反射率的云像元;然后利用近红外与可见光反射率比值检验识别晴空像元;最后建立多角度云检测结果空间融合规则,重新标记有云、晴空和未定像元。以印度洋海区为例进行实验分析,将云检测结果与Buriez方法进行对比,发现检测精度基本相当,而有云像元的识别速度却平均提高约3倍。结果表明:该方法能有效的检测出海洋上空的云像元,满足业务化数据处理的高精度及时效性要求,为后续云微物理特性反演提供可靠的数据源。  相似文献   

抛物Radon变换法近偏移距波场外推   总被引：14，自引：8，他引：6       下载免费PDF全文

王维红  刘洪 《地球物理学进展》2005,20(2):289-293

本文给出了抛物Radon变换的基本原理,以及部分动校正后的CMP道集抛物线近似有效性的证明,基于带限正反最小平方抛物Radon变换的Levinson递推算法,对缺失的近偏移距地震波场进行叠前重建和外推.给出了抛物Radon变换法地震道重建外推的基本原理和叠前地震数据规则化的处理流程,另外对于Radon域均匀采样的情形,本文给出了均匀层状介质和Marmousi模型的近偏移距外推结果,计算结果验证了算法的稳定性和适用性.  相似文献