青藏高原东北缘SKS波分裂研究

利用青藏高原东北缘区域数字地震台网43个台站的远震SKS波形资料,采用最小能量法和旋转相关法得到台站下方上地幔介质各向异性的分裂参数:快波偏振方向(φ)和快慢波时间延迟(δt)。研究结果表明:在塔里木盆地东南缘区域,各向异性快波方向与该区域的断裂走向存在明显的夹角,该盆地向柴达木盆地的俯冲方向一致,各向异性归因为古构造运动遗留下的"化石各向异性",且由于壳幔物质的拆沉作用,推测该区域壳幔之间存在解耦作用;在祁连—河西走廊区,SKS快波偏振方向呈NW-SE,与主要断裂带的走向一致;在西秦岭北缘断裂带附近,观测到快慢波时间延迟有着较大的变化,可能是岩石圈变形和软流圈物质流动共同导致;在鄂尔多斯板块内,快波方向呈NW-SE方向,可能暗示青藏高原深部物质分叉绕流运动。青藏高原东北缘不同区域台站下方的各向异性均具有差异性,进一步证实了青藏高原东北缘地区构造变形的复杂性。     

Variations of the Ionospheric Plasma Parameters Observed by the Ionosonde and Magnetic Station in the Range of Periods of Planetary Waves

Izvestiya, Physics of the Solid Earth - Abstract—Variations of the geomagnetic field and F2-layer critical frequency in the range of periods of planetary waves in winter season are analyzed....     

Global Lightning Activity on the Basis of Inversions of Natural ELF Electromagnetic Data Observed at Multiple Stations around the World

The monitoring of global lightning activity and its spatial and temporal variations is known to be very essential for the study of global warming, the subject of greatest concern to human beings on planet Earth today. As a method of remote sensing for the global lightning distribution, we have proposed an inverse problem by using the data of natural electromagnetic noise in the ELF (extremely low frequency) Schumann resonance (SR) band observed simultaneously at a few stations around the world. The fundamentals of this inversion problem (or ELF tomography) to the SR data have been presented and the first attempt to deduce the global lightning distribution by means of the real SR data has been performed, which has indicated a possibility of snapshots of well-known thunderstorm centers on the globe. This ELF tomography consists of two stages. The first stage is the inversion of the ELF field power spectra to the distribution of lightning intensity by distance relative to an observation point. The obtained distance profiles of intensity of sources at a few stations are used as tomographic projections for reconstructing a spatial distribution of sources in the second stage. Maps of the global lightning distributions constructed by the result of inversions of ELF background field spectra obtained from three stations around the world show that the most active regions vary meridionally on the diurnal time scale being connected mainly with continental areas in the tropics. We do hope that this kind of inversion method to multi-stationed ELF data will be of great importance in the future.     

Teleseismic Source Parameters of the Rigan County Earthquakes and Evidence for a New Earthquake Fault

Two medium-sized earthquakes occurred on 20 December 2010 and 27 January 2011 in Rigan County, Kerman Province, southeastern Iran. According to the dislocation grid search method results, the first event was nearly strike-slip including reverse component (strike 115°, dip 50°, and rake ?5°) whereas the second event had some amount of reverse component (strike 125°, dip 75°, and rake ?5°). Based on synthetic Green’s function deconvolution and aftershock distribution, the down-dip-propagated rupture migrated toward southeast districts with low population distribution, confirming the reason for low casualties. Meanwhile, the aftershock distribution indicates the existence of a new earthquake fault for which we suggest the name “Rigan earthquake fault.” However, the same aftershock distribution indicates that the second mainshock was inevitably triggered by the first one, most probably along the continuation of the Bam earthquake fault.     

Analysis of Signals from an Unique Ground-Truth Infrasound Source Observed at IMS Station IS26 in Southern Germany

Quantitative modeling of infrasound signals and development and verification of the corresponding atmospheric propagation models requires the use of well-calibrated sources. Numerous sources have been detected by the currently installed network of about 40 of the final 60 IMS infrasound stations. Besides non-nuclear explosions such as mining and quarry blasts and atmospheric phenomena like auroras, these sources include meteorites, volcanic eruptions and supersonic aircraft including re-entering spacecraft and rocket launches. All these sources of infrasound have one feature in common, in that their source parameters are not precisely known and the quantitative interpretation of the corresponding signals is therefore somewhat ambiguous. A source considered well-calibrated has been identified producing repeated infrasound signals at the IMS infrasound station IS26 in the Bavarian forest. The source results from propulsion tests of the ARIANE-5 rocket’s main engine at a testing facility near Heilbronn, southern Germany. The test facility is at a range of 320 km and a backazimuth of ~280° from IS26. Ground-truth information was obtained for nearly 100 tests conducted in a 5-year period. Review of the available data for IS26 revealed that at least 28 of these tests show signals above the background noise level. These signals are verified based on the consistency of various signal parameters, e.g., arrival times, durations, and estimates of propagation characteristics (backazimuth, apparent velocity). Signal levels observed are a factor of 2–8 above the noise and reach values of up to 250 mPa for peak amplitudes, and a factor of 2–3 less for RMS measurements. Furthermore, only tests conducted during the months from October to April produce observable signals, indicating a significant change in infrasound propagation conditions between summer and winter months.     

巴基斯坦达尔巴丁(Dalbandin）地震前观测到的电离层foF2异常变化

电离层foF2变化对地震反应非常敏感,与地震有关的电离层扰动变化结果似乎非常有望用于地震短期预测。格林威治时间2011年1月18日20:23分,一次7.2级的大地震发生在巴基斯坦的达尔巴丁(28.73oＮ, 63.92oＥ）。本文研究中,我们必须利用架设在巴基斯坦的伊斯兰堡（33.78oN, 73.06oE）、玛尔坦（32.26oN,71.51oE）和卡拉奇（24.89oN,67.02oE）三个垂直探测台站获得的白天（08:00 a.m. - 05:00 p.m.）小时值数据找出地震前的foF2异常变化特征。结果显示,在达尔巴丁地震前几天,foF2出现了显著变化;并且距离震中最近的台站观测到的频率与幅度异常变化大于较远的位于孕震区边缘的台站。尽管地震异常特征显著,但增加其它电离层参数可以提高foF2异常的高置信度水平。     

Azimuthal anisotropy in lithosphere on the Chinese mainland from observations of SKS at CDSN

Ａｚｉｍｕｔｈａｌ　ａｎｉｓｏｔｒｏｐｙ　ｉｎ　ｌｉｔｈｏｓｐｈｅｒｅ　ｏｎ　ｔｈｅ　Ｃｈｉｎｅｓｅ　ｍａｉｎｌａｎｄ　ｆｒｏｍ　ｏｂｓｅｒｖａｔｉｏｎｓ　ｏｆ　ＳＫＳ　ａｔ　ＣＤＳＮ（郑斯华）（高原）Ａｚｉｍｕｔｈａｌａｎｉｓｏｔｒｏｐｙｉｎｌｉｔ...     

Observed Characteristics of Regional Seismic Phases and Implications for P/S Discrimination in the European Arctic

—?In this paper, we use data from seismic stations operated by NORSAR, the Kola Regional Seismological Centre (KRSC) and IRIS to study the characteristics of regional phases in the European Arctic, with emphasis on the P/S ratio discriminant. While the detection and location capability of the regional station network is outstanding, source classification of small seismic events has proved very difficult. For example, the m _b ?=?3.5 seismic event near Novaya Zemlya on 16 August, 1997 has been the subject of extensive analysis in order to locate it reliably and to classify the source type. We consider the application of the P/S discriminant in the context of this event and other events observed at regional distances in the European Arctic. We show that the P/S ratios of Novaya Zemlya nuclear explosions measured in the 1–3?Hz filter band scale with magnitude, indicating a need for caution and further research when applying P/S discriminants. Using mainly data from the large NORSAR array, we note that observed P/S amplitude ratios in the European Arctic show large variability for the same source type and similar propagation paths, even when considering closely spaced observation points. This effect is most pronounced at far regional distances and relatively low frequencies (typically 1–3?Hz), but it is also significant on closer recordings (around 10 degrees) and at higher frequencies (up to about 8?Hz). Our conclusion from this study is that the P/S ratio at high frequencies (e.g., 6–8?Hz) shows promise as a discriminant between low-magnitude earthquakes and explosions in the European Arctic, but its application will require further research, including extensive regional calibration and detailed station-source corrections. Such research should also focus on combining the P/S ratio with other short-period discriminants, such as complexity and spectral ratios.     

1997—2016年中国大陆地区地磁台站观测环境变化定量分析

本文利用CHAOS-6地磁场模型计算1997—2016年中国大陆地区34个地磁台站模型值,分析比较模型计算值与台站实测值之间的差异,利用国际参考场模型IGRF12计算结果进行佐证。结果表明:地磁异常场模量△T作为地磁台站观测环境的一种标志,年变化显示:①中国大陆地区34个地磁基准台绝大部分位于地磁正常区或弱磁异常区,只有少数几个地磁台位于强磁异常区;②判断1个地磁台的地磁场环境,只测量总强度（F）是不够的,必须进行三分量绝对观测,利用地磁异常场模量△T评价地磁台的地磁场环境更全面、更科学合理。     

Time Variations in the Parameters of Dynamic Systems of Geodeformation Processes

Izvestiya, Physics of the Solid Earth - The variability of a correlation dimension parameter of geophysical fields is studied in the tectonically active region of the Parkfield segment of the...     

Variations in Ionospheric Parameters during the Formation of a Polarization Jet

Geomagnetism and Aeronomy - The calculation results and experimental data on the formation and development of a polarization jet in subauroral latitudes are compared. It is shown that the...     

Correlation of the Cosmic-Ray Cutoff Rigidity with Heliospheric and Geomagnetic-Activity Parameters at Different Phases of a Magnetic Storm in November 2004

Geomagnetism and Aeronomy - The correlation of the variations in geomagnetic cutoff rigidity of cosmic rays ΔR with the interplanetary medium parameters and geomagnetic activity indices Dst...     

汶川8.0级地震天水前兆资料异常特征及震情分析与研究

通过对天水地区监测和收集的2008年前兆资料整理分析,在汶川8.0级地震前,天水电磁和地下流体等前兆测项均有明显短临异常,同震效应突出。本文在回溯总结这些异常的基础上提出震情分析的思路和问题探讨,对今后本地区的地震趋势判断提供参考。     

利用远震接收函数反演山西地区台站下方的地壳厚度及泊松比

利用2008—2013年山西数字地震台网远震宽频带记录波形资料,运用H-Kappa叠加方法得到各台站下方的地壳厚度和波速比。研究结果表明,山西地区地壳厚度存在明显的差异。研究区内地壳平均厚度约39km,南北地壳厚度变化幅度较大,其中SHZ(上皇庄台)地壳厚度最大为43km,ANZ(安泽台)地壳厚度最小为36km,南北两端差异达7km。泊松比值在0.24~0.31之间变化,与全球的泊松比估计值相当。山西的地壳厚度与地表地形存在着明显正相关,而地壳厚度和泊松比则呈现负相关的关系。     

中国大陆GPS连续观测站测得的日本9.0级地震同震位移与震前变化

利用中国大陆GPS连续观测站资料, 获取了2011年3月11日日本9.0级地震造成的连续站同震位移。 计算结果表明, 位于我国东部尤其是东北地区的台站在水平方向都有明显的同震位移, 且离震中越近同震位移量越大, 其中绥阳站的水平同震位移量最大, 达到33 mm。 通过对时间序列分析发现, 有明显同震位移的连续站, 震前水平方向的运动速度都有放缓的趋势, 可能是一种形变前兆现象。 这些GPS观测到的同震位移及震前运动速度异常, 对于进一步研究前兆地壳运动、 地震动力学特征以及精化中国大陆地壳运动速度场都有重要意义。     

华北克拉通中部过渡带SKS波分裂研究:鄂尔多斯东南角的局部软流圈绕流

本文对布设在华北克拉通东西两块体交界区域的宽频带流动地震观测台阵和部分固定台站的远震波形记录开展了SKS波分裂研究.结果显示,鄂尔多斯块体内部的各向异性比较弱,剪切波分裂导致的时间延迟一般小于0.7 s.鄂尔多斯块体东缘的山西断陷带和太行山以及华北平原西部均表现出了比较强的各向异性,时间延迟大于1.0 s.特别是在太行山地区观测到的ENE趋向的快波偏振方向明显不同于鄂尔多斯块体和华北平原地区的近E-W和ESE方向的快波偏振方向.在华北克拉通东西两块体交界过渡带的太行山地区观测到的显著上地幔各向异性及变化可能对应于围绕鄂尔多斯块体东南角的局部软流圈绕流,而后者可能起因于鄂尔多斯块体的逆时针旋转以及青藏高原软流圈沿秦岭大别造山带向东的流动.     

Variation of Shear-wave Residuals and Splitting Parameters from Array Observations in Southern Tibet

—A tight array of seismographs spanning a 500 km traverse of southern Tibet resolved anisotropy from SKS with a spatial variation of its direction and an increase northward of the splitting delay, as well as of its first arrival residual. Both waves split by velocity anisotropy are slow relative to P and their waveform analysis may be interpreted to suggest attenuation anisotropy. The array here provides examples of residuals and splitting of other S waves which do not tightly conform to the anisotropy assumed in the simplest model of olivine of transverse isotropy with horizontal symmetry axis. S waves are also split, with parameters which vary along the array, and hence are relevant to near-receiver structure like those of SKS. Their splitting delay, for non-vertical incidence and polarization, appears larger than that for SKS. Residuals of S-wave first arrivals and splitting delays increase less northwards for S than SKS. Anisotropy with a slow vertical axis may account for these observations. Its origin may be related to horizontal shear or flow in low-velocity layers.     

用远震体波宽频带记录分析1993年10月2日中国新疆南部Mb6．2地震的震源过程

远震体波宽频带记录可以用来研究震源参数和破裂过程。利用宽频带地震记录的Ｐ波振幅，可以找到一种较方便地得到一次中强地震的震源机制解的计算方法。１９９３年１０月２日中国新疆南部Ｍｂ６．２地震是一个较为复杂的事件，利用宽频带波形资料和本文提出的一种简化的计算震源两个子事件相对位置的方法分析后认为，这次事件实质上是两次破裂的结果。Ｍｂ６．２地震事件发生前约２．３秒，有另一个小地震事件发生，两个事件之间的相对距离约为５．５ｋｍ，沿破裂面接走向以顺时针方向计，小地震事件相对于主破裂之间的方位是２９５°。对于以上提出的两种算法的结果，我们进行了宽频带地震波形正演拟合检验，证明了算法的有效性。新疆是个多地震地区，本文以新疆南部这次Ｍｂ６．２地震为中心，对方圆２００ｋｍ范围内的历史地震序列作了分析，并对这次地震的构造意义进行了讨论。     

Cycle Variations in the Photospheric and Interplanetary Magnetic Field and Solar Wind Parameters

Geomagnetism and Aeronomy - The influence of cycle changes in the polar and nonpolar photospheric magnetic fields on variations in the interplanetary magnetic field (IMF) and the solar wind...