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RECONSTRUCTION OF TEMPERATURE SERIES OF NORTH CHINA FROM 1380s TO 1980s

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Science China Chemistry 1991年第6期34卷 751-759页

作者：王绍武 department of geophysics Peking University Beijin 100871 PRC

The decade mean temperature anomaly series was reconstructed on the basis of histori-cal documents recorded in substantive local gazetteers. Firstly, the severity of the cold weath-er events such as snowing and severe frost, which were frequently described in gazetteers,was estimated by using modern instrumental temperature observations. Secondly, the assort-ed cold events were classified into three classes according to the severity. the severity indexof them being --0.5, -- 1.0 and --2.0 respectively. The severity index was found fot eachseason since 1380 AD while there were somc descriptions of cold events. Finally, the re-gression coefficients between the decade sum of severity index and decade mean seasonal tem-perature anomalies was calculated. It shows that the severity index of--1 is equal to --0.2℃of the temperature anomaly. Then the decade mean seasonal temperature anomaly serieswas reconstructed from the 1380s (1380--1389 AD) to the 1980s. The series shows that therewere two cold periods; one between the 1550s and 1690s, another during the 1800s--1860s. Thelowest decade mean temperature anomaly reacked -- 1.8℃ in winter and varicd from 1--1.1to --1.4℃ for other seasons. In spring and summer series, the first cold period was mani-fested well. In autumn tbe second cold period was prominent. But in winter both the firstand the second cold periods were clearly observed. The timing of the cold periods found inthe present paper was earlier by 70 and 40 years respectively than that found by Chu Kochen(1973), which was mainly based on winter temperature documents in South China. It sug-gests that the timing of the cold period in the Litt1e Ice Age varied from place to placeeven within the Chinese territory.

关键词： climate change paleoclimate Little Ice Age climate reconstruction

STUDY ON ATMOSPHERIC TRACE GAS NO_2

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Science China Chemistry 1990年第9期33卷 1124-1135页

作者：张呈祥赵柏林毛节泰 department of geophysics Peking University Beijing 100871 PRC

The content of NO_2 in the atmosphere is one of the important factors for atmospheric environmental appreciation. An automatic solar spectrophotometer (ASS) system has been developed in order to observe the content of NO_2 in the atmosphere. The column content of atmospheric NO_2 has been obtained by use of radiative transfer equation and maximum resembled method, through the ground-based observation of direct solar radiative spectrum of 4470—4490. Some months' observations of NO_2 have been made in the suburbs of Beijing. The results have been discussed here.

关键词： NO_x NO_2 atmospheric trace gas

Stress interactions between normal faults and adjacent strike-slip faults of 1997 Jiashi earthquake swarm

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Science China Earth Sciences 2008年第3期51卷 431-440页

作者： CHEN John YongShun department of geophysics School of Earth and Space Sciences Peking University China

During a 4-month period starting from 21 January, 1997, an earthquake swarm of seven major events (Ms≥6.0) struck the Jiashi region at the northwestern corner of the Tarim Basin in Xinjiang,, China. Previous relocation studies suggested that these strong earthquakes had occurred along at least two parallel rupture zones. According to the relocated hypocenters and focal mechanisms of the events, we have constructed fault models for these seven earthquakes to calculate the Coulomb stress changes produced by each of these events. Furthermore, we extended our model calculations to include an ad- jacent 1996 Ms=6.9 Artushi earthquake, which occurred one year before the Jiashi earthquake swarm. Our calculations show that the Coulomb stress change caused by the preceding events was around 0.05 MPa at the hypocenter of the 4th event, and higher than 0.08 MPa at the hypocenters of the 2nd, 3rd, 5th and 6th events. Our results reveal a Coulomb stress interactive cycle of earthquake triggering between two adjacent normal and strike-slip faults.

关键词： Jiashi earthquake swarm normal fault strike-slip fault Coulomb stress change earthquake triggering

The variation in the magnetic fluctuation anisotropy across the front boundaries of magnetic clouds and its geomagnetic response

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Chinese Science Bulletin 2002年第10期47卷 863-867页

作者： LIU Rui & WEI Fengsidepartment of geophysics, Peking University, Beijing 100871, China Lab for Space Weather, Center for Space Science and applied Research, Chinese Academy of Sciences, Beijing 100080, China department of geophysics Peking University Beijing China Lab for Space Weather Center for Space Science and Applied Research Chinese Academy of Sciences Beijing China

A statistical study of magnetic fluctuations near the front boundaries of magnetic clouds is approached with the method of Minimum Variance Analysis, based on the data of ImpS and Wind spacecraft. New discoveries are that (1) fluctuation anisotropy tends to increase across the front boundaries of magnetic clouds; (2) there is a good correlation between the fluctuation anisotropy and the geomagnetic activity indices; and (3) in some cases, although there is southward field component immediately after the front boundary, Kp index descends (or Dst index ascends) with a corresponding decrease of the fluctuation anisotropy; in other cases with no distinct southward field component, Kp index ascends (or Dst index descends) with a corresponding increase of the fluctuation anisotropy. Thus we suggest that the fluctuation anisotropy might be a useful indicator in diagnosing the magnetic activities of magnetic clouds.

关键词： front boundary of magnetic clouds geomagnetic activity fluctuation anisotropy.

The quest for conditional independence in prospectivity modeling： weights-of-evidence, boost weights-of-evidence, and logistic regression

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Frontiers of Earth Science 2016年第3期10卷 389-408页

作者： Helmut SCHAEBEN Georg SEMMLER department of geophysics and Geoinformatics TU Bergakademie Freiberg Freiberg 09596 Germany

The objective of prospectivity modeling is prediction of the conditional probability of the presence T = 1 or absence T = 0 of a target T given favorable or prohibitive predictors B, or construction of a two classes {0,1} classification of T. A special case of logistic regression called weights-of-evidence （WofE） is geolo- gists＇ favorite method of prospectivity modeling due to its apparent simplicity. However, the numerical simplicity is deceiving as it is implied by the severe mathematical modeling assumption of joint conditional independence of all predictors given the target. General weights of evidence are explicitly introduced which are as simple to estimate as conventional weights, i.e., by counting, but do not require conditional independence. Complementary to the regres- sion view is the classification view on prospectivity modeling. Boosting is the construction of a strong classifier from a set of weak classifiers. From the regression point of view it is closely related to logistic regression. Boost weights-of-evidence （BoostWofE） was introduced into prospectivity modeling to counterbalance violations of the assumption of conditional independence even though relaxation of modeling assumptions with respect to weak classifiers was not the （initial） purpose of boosting. In the original publication of BoostWofE a fabricated dataset was used to ＂validate＂ this approach. Using the same fabricated dataset it is shown that BoostWofE cannot generally compensate lacking condi- tional independence whatever the consecutively proces- sing order of predictors. Thus the alleged features of BoostWofE are disproved by way of counterexamples, while theoretical findings are confirmed that logistic regression including interaction terms can exactly com- pensate violations of joint conditional independence if the predictors are indicators.

关键词： general weights of evidence joint conditionalindependence naive Bayes model Hammersley-Cliffordtheorem interaction terms statistical significance

Modal solutions in stratified multi-layered fluid-solid half-space

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Science China Earth Sciences 2002年第4期45卷 358-365页

作者：陈蔚天陈晓非 1. department of geophysics Peking University 100871 Beijing China

A new systematic and efficient algorithm to calculate the modal solutions of multi-lay- ered ocean-Earth model is presented. Our algorithm distinguishes itself as terseness of formulation, efficiency in numerical computation, and stableness at high frequencies, thus, thoroughly solving the problem of loss-of-precision at high frequencies. This new algorithm is expected to be very useful in studying the surface waves propagating in ocean-Earth model and other related topics.

关键词： normal mode, multi-layered ocean-Earth model, surface waves.

Discussion on origin of Pn velocity variation in China and adjacent region

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Acta Seismologica Sinica(English Edition) 2004年第1期17卷 1-11页

作者： PEI Shun-ping(裴顺平) XU Zhong-huai(许忠淮) WANG Su-yun(汪素云) Computational Geodynamics Laboratory Department of Geophysics Peking University Beijing 100871 China Institute of Geophysics China Seismological Bureau Beijing 100081 China Institute of Geophysics China Seismological Bureau Beijing 100081 China

Pn velocity lateral variation and anisotropy images were reconstructed by adding about 50 000 travel times from the regional seismic networks to the datum set of near 40 000 travel times from National Seismic Network of China used by WANG, et al. We discussed the relation of Pn velocity variation to Moho depth, Earths heat flow, distribution of Cenozoic volcanic rock and the result of rock experiment under high pressure and high temperature. The result of quantitative analysis indicates that Pn velocity is positively correlated with the crust thickness and negatively correlated with the Earths heat flow. Two linear regression equations, one between Pn velocity and crust thickness, and the other between Pn velocity and heat flow, were obtained. The rate of variation of Pn veloc-ity vP with pressure P, Pv/p, estimated from the velocity variation with crust thickness Hv/p, is close to the result obtained from the rock experiment under high pressure and high temperature. If the effect of crust thick-ness on Pn velocity is deducted from the velocity variation, then the low Pn velocity beneath Qinghai-Xizang pla-teau is more notable. The low Pn velocity regions well agree with the Cenozoic volcanic rock. In the several re-gions with significant anisotropy, the direction of fast Pn velocity is consistent with the orientation of maximum principal crustal compressive stress, and also with the direction of present-day crustal movement. It indicates that the fast Pn velocity direction may be related to the deformation or flow of top mantle material along the direction of maximum pressure.

关键词： Pn tomography anisotropy China and adjacent region

Crack mystery of the damaging Kumamoto earthquakes

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Science Bulletin 2016年第11期61卷 868-870页

作者： Dapeng Zhao Xin Liu department of geophysics Tohoku University College of Marine Geosciences Ocean University of China

The 2016 Kumamoto earthquake(M 7.3 in the Japan Meteorological Agency(JMA)scale)sequence wrote a new chapter of active seismotectonics and subduction dynamics in the Japan *** earthquake sequence,

关键词：地震序列破坏性日本气象厅裂缝活动构造 Moto 动力学上地壳

INVERSION OF A NONLINEAR DYNAMICAL MODEL FROM THE OBSERVATION

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Science China Chemistry 1991年第10期34卷 1246-1251页

作者：黄建平衣育红 department of geophysics Peking University Beijing 100871 PRC

A technique for inversion of a nonlinear dynamical model from the observations has been developed, and examined by using the Lorenz system. The results show that the Lorenz system can be accurately inversed by using the observation data set. This technique will be broadly used in establishing the nonlinear dynamical model from an actual data set.

关键词： observation data model inversion nonlinear dynamical model.