用介质Q值、剪切应力和震源参数研究北京周围地区中强地震的短临预报

通过北京周围地区中强地震前后介质Ｑ值、剪切应力和小震（Ｍ＿Ｌ≤３．０）震源参数的变化的研究，给出一种中强地震短临预报的新方法。     

湖北江汉盆地潜江凹陷深层地下卤水水文地球化学研究

潜江凹陷是我国东部的一较大型油盐沉积盆地．凹陷内的Ｑ组（渐新统）含盐系地层是一套内陆盐湖相沉积，其中不仅蕴藏着丰富的石油和固体盐类，而且卤水资源也十分丰富．卤水为高矿化度、高ＳＯ含量、低Ｃａ（２＋）、Ｍｇ（２＋）含量的硫酸盐型陆相古盐湖沉积卤水．卤水的ｐＨ值平均为５．６６，总矿化度平均为２８３．２５克／升．水盐体系主要为Ｎａ，Ｋ／／Ｃｌ，ＳＯ４－Ｈ２Ｏ，古卤水水化学类型为Ｎａ２ＳＯ４亚型．卤水中含近２８种化学成分，ＳＯ的平均含量达９６６５．８毫克／升，Ｃａ（２＋）和Ｍｇ（２＋）的平均含量才分别为８９９．４毫克／升和１７３．８毫克／升．Ｋ、Ｂ、Ｌｉ、Ｂｒ、Ｉ等的含量较大，Ｋ、Ｂ、Ｌｉ的含量随Ｃｌ浓度的增加而增加，Ｂｒ、Ｉ的含量随矿化度的增加而增加，随ＳＯ浓度的增加而减少．卤水中绝大多数离子的含量在沉积盆地浓缩中心区大，在理深较大的第四、五、六水层高．     

大同地震序列的尾波Q值变化特征研究

要：利用大同台网1990～2000年的地震记录资料,系统地分析了大同地震序列尾波Q值随时间的变化,着重分析了尾波Q值在中强地震前的短期变化特征。结果表明,分频率的尾波Q值在几次中强地震前都不同程度出现了低值,并与大同震情“窗口”出现同步的异常。     

Estimates of coda Q attenuation in the João Câmara area (Northeastern Brazil)

S coda wave of seventy-four local earthquakes recorded in a network of ten seismic stations were used to calculate coda Q attenuation (Q_c) in the João Câmara area (northeastern Brazil). The estimates show Q_c as a strong function of frequency in the range from 6.0 to 20.0 Hz. We found out that Q_c in João Câmara has a functional form given by Q_c= Q₀ f, where Q₀= 151 ± 99 and = 0.98 ± 0.05. If the standard deviations are taken into account,we conclude that there are no relevant changes in both Q₀ and values from one station to another. The estimated Q₀ values at the different stations suggest that the Samambaia fault is a boundary between two different seismic attenuation zones. In one side of the fault (left), where stations were installed in Pre-Cambrian terrain and thick sedimentary layer, the seismic attenuation is stronger than in the other side (stations installed in thin sedimentary layer and limestone outcrop).The anomalous Q₀ values in the left side of the Samambaia fault can be explained due to the presence of a shallow conductive layer in the upper crust( 10 km), such as proposed by Padilha et al. (1992). According to our results, if there is a conductive layer in the area, it probably spreads over João Câmara city and surrounding regions.However, more detailed investigation either with seismic methods (seismic attenuation,3D tomography with P and/or S wave velocities) or with other geophysical methods is needed to interpret the observed differences in Q₀ values between the two sides of the Samambaia fault.     

山西地区非弹性衰减系数、场地响应和几种震源参数的研究.

根据山西数字地震台网14个地震台的310条波形资料，研究了山西地区的非弹性衰减系数；采用Atkinson和Moya方法，研究了各台的场地响应和几种震源参数，并对这两种方法的反演结果进行了对比分析. 得到山西地区非弹性衰减Q值随频率f的关系为Q(f)=323.2f 0.506；得到的14个台站的场地响应均没有显示出明显的放大效应，这与山西台站均处于岩石地基相符；得到了拐角频率与地震矩、地震矩与应力降、震源半径与应力降之间存在依赖关系.      

渭河断陷盆地及邻近地区的Q值速度场分布特征与地震活动性

利用西安数字遥测地震台网记录的数字地震资料．采用P↑-波初动半周期方法．得到了渭河断陷盆地及邻近地区的Q值分布。结果表明，Q值分布与20km深度P↑-波速度分布有较好的一致性．并与该区域的地震活动性密切相关。     

Surface-wave group-delay and attenuation kernels

We derive both 3-D and 2-D Fréchet sensitivity kernels for surface-wave group-delay and anelastic attenuation measurements. A finite-frequency group-delay exhibits 2-D off-ray sensitivity either to the local phase-velocity perturbation  δ c / c   or to its dispersion  ω(∂/∂ω)(δ c / c )  as well as to the local group-velocity perturbation  δ C / C   . This dual dependence makes the ray-theoretical inversion of measured group delays for 2-D maps of  δ C / C   a dubious procedure, unless the lateral variations in group velocity are extremely smooth.     

The attenuation mechanism of seismic waves in northwestern Himalayas

We analysed local earthquake waveforms recorded on a broad-band seismic network in northwestern Himalayas to compute the intrinsic and scattered attenuation parameters from coda waves. Similar to other tectonically active and heterogeneous regions, attenuation-frequency relation for western Himalaya is   Q ⁻¹ _c = (113 ± 7)  f ^(1.01±0.05)  where   Q_c   is the coda Q parameter. Intrinsic  ( Q ⁻¹ _i )  and scattering  ( Q ⁻¹ _s )  attenuations was separated using   Q_c   and direct S -wave Q data  ( Q_d )  . It is observed that estimated   Q ⁻¹ _c   is close to   Q ⁻¹ _i   and both of them are much larger than   Q ⁻¹ _s   suggesting that coda decay is predominantly caused by intrinsic attenuation. At higher frequencies, both the attenuation parameters   Q_c   and,   Q_d   are similar indicating that coda is predominantly composed of back-scattered S waves at these frequencies.     

Fractal dimension of changes in the solar magnetic field energy and quasi-biennial solar activity variations

Using the data of 1960–1999 on solar magnetic fields on the source surface and the Higuchi method, the fractal dimension of changes in the solar magnetic field energy at various heliolatitudes and in different time intervals is analyzed. The fractal dimension obtained on a moving 1-year interval displays substantial time variations. The 11-year cycle, which dominates at high latitudes, and quasi-biennial variations (QBVs), which dominate at low latitudes and are similar to QBVs of solar activity indices, are traced in these variations. Thus, solar QBVs that appear in all heliomagnetic activity indices are also present in the fractal structure of the solar magnetic field variations.