The Q value variations in the preparing pro－cess of rock rupture

ＴｈｅＱｖａｌｕｅｖａｒｉａｔｉｏｎｓｉｎｔｈｅｐｒｅｐａｒｉｎｇｐｒｏ┐ｃｅｓｏｆｒｏｃｋｒｕｐｔｕｒｅＢＩＮＷＡＮＧ１）（王彬），ＺＨＡＯ－ＹＯＮＧＸＵ１）（许昭永），ＪＩＮ－ＭＩＮＧＺＨＡＯ１）（赵晋明）ＹＩ－ＬＩＨＵ２）（胡毅力）１）Ｓｅｉ...     

富蕴水磨沟探槽的孢粉组合特征及其意义

本文应用孢粉分析对富蕴水磨沟探槽的地层年代和古环境进行了探讨,认为富蕴地区在新冰期第一期活动中气候干净,为寒冻荒漠植被;在大西洋期为暖干气候,生长了草原化荒漠植被;在其后的新冰期活动中为冷湿气候,发育了灌丛草原植被。结合新疆特殊的地理条件,将上述环境演变过程与国内外全新世气候波动研究结果相比较,并参考有关(14)~C数据,作者认为该探槽中发现的第一次古地震活动应晚于6000a,B.P,第二次古地震活动似应发生于2500a,B.P之后。     

Lg amplitude ratios H/Z and station terms in the six eastern provinces of China

Using the data set of about 1 Hz Lg amplitudes from 80 stations in the six eastern provinces of China, the ratios of horizontal to vertical amplitude of Lg waves,H/Z are determined. The mean lg(H/Z)-value is equal to 0.13. For the station bases of soft deposit,granite and sedimentary rock, lg(H/Z)-values average 0.55, 0.04 and 0.10, respectively. For the three kinds of station bases, the station terms of horizontal amplitude,C _h average 0.65, −0.09 and 0.00; that of vertical amplitude,C _z average 0.32, −0.04 and 0.00, respectively. There are the relations betweenC _h ,C _z and lg(H/Z):C _h =0.01+2.10C _z andC _h =−0.15+1.46 lg(H/Z). The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 281–286, 1991. Project sponsored by the Chinese Joint Seismological Science Foundation.     

A discussion on the amplitude ratios of PP and P waves for earthquakes with different focal mechanisms

Using the WKBJ approximation method we calculate the synthetic teleseismograms of P and PP waves to match the observed ones of six large Chinese earthquakes with known focal mechanisms: Tibet earthquake of July 14, 1973; Haicheng earthquake of February 4, 1975; Songpan earthquakes of August 16, 1976, August 21, 1976 and August 23, 1976 and Nignhe earthquake of November 15, 1976. The focal mechanism of the Tibet earthquake is discussed to examine the technique used in the calculation. We note that the amplitude ratios of PP and P waves (A _PP/A _P) have different characteristics for dip—slip events and strike—slip events within certain epicentral distances. We calculate the synthetic teleseismograms of P and PP waves for the strike—slip and dip—slip events with fault angles of 330°, 240° and 0°, focal depths of 8 km, 17 km and 24 km, at the assumed station with an azimuth of 310° and epicentral distances from 40°; to 80°. The diagrams of maximum amplitude ratios of PP and P waves (A _PP/A _P) versus distances are given. The possibility to use the (A _PP/A _P) values to give an approximate estimation for the focal mechanism type is discussed. This work may be useful for determining the focal mechanism type for those earthquakes which have only few records such as the Chinese earthquakes from the 1930s to 1960s. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 150–160, 1991.     

蘑菇状金伯利岩体上视电阻率异常特征

简要论述了选择低阻蘑菇状模型模拟金伯利岩体的地质依据,着重分析了联合剖面装置、对称四极测深ρ_3异常特征。     

Amplitude Response of a LCR Gravimeter with Feedback at Periods of Microseisms and Earthquake Waves

The amplitude response of a LCR gravimeter with the SRW-E feedback was determined on a vertical vibrating platform. The ink-pen recorder was connected parallel with the digital voltmeter input to obtain an analog response of the gravimeter to the harmonic motion of the base with a peak-to-peak amplitude of 10 m and periods excited in an interval of 4 - 10 s as by the ground motion of meteorological microseisms, and in the interval 10 -100 s as by surface waves of distant strong earthquakes. In the first interval, an unexpected maximum of the amplitude response was observed with the double amplitude of apparent 6,5 Gal (6.5 × 10 _–8 m/s ² ) at a period of 4.8 s, and a baseline shift with the amplitude of–64Gal was observed at the same period. The value of this direct component cannot be separated from the effect of the Earth's gravity field. In the second interval, the amplitude response of the gravimeter displayed one expected maximum at a period of 40 s with the double amplitude of 8.1Gal. At the usual level of microseisms with a peak-to-peak amplitude of up to 2 m the fluctuation of the gravimeter on the direct baseline shifted by –4.9 Gal was estimated at 1 Gal. With typical Rayleigh surface waves with periods of 20 s and double amplitudes of up to 100 m, the fluctuation reached 67 Gal.     

层序地层研究产生的地层学新观点、新概念和新方法——兼论建立新一代年代地层表

层序地层学在地层划分、对比、分类和级别体系等地层学根本理论问题上给地层学带来了新认识、新概念和新方法。全球层型剖面和点(GSSP)可建在层序界面的整合部位,从而将传统的自然界线(或不整合面)、层序界面和GSSP三者有机结合起来,使得年代地层界线成为可在野外识别和追索的界线。论证了层序地层是独立存在于岩石地层和年代地层之间的地层类别和包含这三个基本地层类别的新的三重地层分类方案。阐述用层序地层界线优化各类原有年代地层和岩石地层界线的原理和方法,探讨和阐述了新的地层学体系和建立新一代年代地层表的途径和方法。     

二叠-三叠纪之交牙形石生态新模式

通过对浙江长兴煤山剖面二叠－三叠系界线层沉积相分析及牙形石演化规律研究,提出了该时期Ｃｌａｒｋｉｎａ（Ｎｅｏｇｏｎｄｏｌｅｌａ）,Ｈｉｎｄｅｏｄｕｓ两类重要牙形石属的生态新模式．（１）Ｃｌａｒｋｉｎａ是一种底栖自由游泳生物,可出现于远岸浅海至盆地相较深水环境;（２）Ｈｉｎｄｅｏｄｕｓ是一种洋面浮游型生物,死亡之后可沉于海底的滨、浅海至深水盆地各种环境之中,并可渡过二叠－三叠纪之交海底缺氧事件这一难关,在早三叠世得到发展;因此,Ｈｉｎｄｅｏｄｕｓ可作为全球二叠－三叠系界线划分对比的可靠证据．     

Incremental Growth of Plains-Type (Compactional) Folds in a Cratonic Environment as Revealed by the Sedimentary Sequence

The enigma of the origin and development of plains-type folds, as they were christened in the early 20th Century, essentially has been solved. The folds, a considerable distance from the tectonic disturbance, were formed by draping of sediments over differentially displaced Precambrian basement fault blocks. These Precambrian basement fault blocks controlled the location, size, and shape of the folds. Forces were transmitted through the rigid basement causing readjustment along the indigenous fracture/fault pattern formed much earlier. In the U.S. Midcontinent, the crystalline basement is overlain by a thin veneer of sediments, and once the structures were formed, they continued to develop as evidenced by features in the overlying sediments. As the stress was transmitted through the basement and then relaxed, the fault blocks moved differentially in concert to these outside forces. Sediment compaction and nondeposition over structural topographic highs reacted accordingly to form the features as seen today. To determine the structural history, structural closure on different horizons on the anticline is plotted in their appropriate stratigraphic position at depth. This gives a compaction line for each tectonically coherent segment. Similar segments show a relatively straightline with offsets at major unconformities indicating breaks in the continuum. It is at these breaks that the section can be stretched until the compaction line matches as a continuum with the resulting gap giving the approximate amount of missing section for that part of the rock column. Conversely, the amount of closure on a structure at depth for each line segment can be estimated by extrapolating downward in that segment. This technique to determine depth of burial and thus the amount of missing stratigraphic section from well data at numerous locations has been compared with estimates made by other methods and the results are similar. Where no other data are available or for quick estimates, then, it is proposed that this approach will give reasonable results and that the values can be used as a constraint in basin modeling.     

现代植物炭屑形态的初步分析及其古环境意义*

通过对23种现代植物炭屑的观察、测量以及对草本、木本炭屑模拟破碎试验后的测量统计发现:现代植物炭屑形态根据其长宽比(L/W)和形态特征可以分为3个类型:1)草本型炭屑,L/W最大,平均为10.2±1.3, 呈长-薄条型、针型、簇纤维型,边缘及断口截然,棱角分明,有些具有气孔构造,很少有不规则的形态出现; 2)木本型炭屑(灌木+乔木),L/W较小,平均3.1±0.2,多呈方~长方型或立方体型,边缘多参差不齐,有些横向断口有粗大木纤维露出,相对致密; 3)阔叶类植物叶片炭屑,L/W最小,平均1.7±0.1,薄片状、网状,絮状,易碎。进一步通过对6个典型草原和森林表土样品的实验室分析,发现现代土壤中的炭屑颗粒大小相对现代植物炭屑颗粒大小总体有所减小,但草原土壤中炭屑长宽比相对森林土壤炭屑仍然较大,土壤中炭屑形态和部分结构鉴别特征仍能保留。表明L/W值与炭屑结构特征可以用来区分多数草本与木本植物炭屑。在此基础上,通过对黄土高原渭南剖面S₁以来不同层位12个地层样品的炭屑形态分析,初步研究了不同草本、木本植物炭屑形态变化的特点和环境意义。