《测绘学报》1998年分类总目次     

On Distributed Wide Area Differential GPS Real Time Kinematic Positioning System 《测绘学报》1998,27(4)

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P- and S-Wave Site Response of the Seismic Network RESNOM Determined from Earthquakes of Northern Baja California, Mexico     

R. R. Castro  RESNOM Working Group 《Pure and Applied Geophysics》1998,152(1):125-138

—We determined the response to P- and S-wave incidence of the permanent stations of the seismic network of Baja California (RESNOM) using two independent methods. We selected 65 events with magnitudes between 2.2 and 4.8 and hypocentral distances ranging between 5 and 330 km. The site response of the ten stations analyzed was first estimated using average spectral ratios between the horizontal and the vertical components of motion (H/V ratios). As a second approach we performed a simultaneous inversion for source and site. In order to invert the spectral records to determine the site response, we made an independent estimate of the attenuation for two different source-station path regions. Then we corrected the spectral records for the attenuation effect before we made the inversion. Although the average H/V ratio of many sites is inside the error bars of the site response estimated with the spectral inversion, the spectral inversion tends to give higher values. For the S wave some sites show similar frequency of predominant peak when comparing the responses obtained with both methods. In contrast, for the P waves the H/V ratios disagree with the results of the inversion. In general, the site response of the stations is strongly frequency dependent for both P and S waves. We also found that the natural frequency of resonance of the sites is near 0.5 Hz for P and near 0.8 Hz for the S waves.  相似文献   

Radio observations of the 1968 September solar eclipse     

Solar Eclipse Radio Observation Group 《Chinese Astronomy and Astrophysics》1982,6(4):311-318

This paper summarizes the analysis of the radio observations of the solar eclipse at wavelengths 3.2, 11.1 and 21 cm in Xinjiang, on 1968 Sept. 22. From the observations, we have determined the flux densities, angular diameters and heights of the localized radio sources on the solar disk, circumstances of the radio eclipse, equivalent radius of the radio Sun and certain features of a small radio burst that occurred during the eclipse. We have also investigated the correlation between the flux density of the localized sources and the activity of the active regions, as measured by the integrated brightness of plages and the sunspot area.  相似文献   

Heat flow variation with depth in Poland: evidence from equilibrium temperature logs in 2.9-km-deep well Torun-1     

Jacek?Majorowicz  Jan??afanda  Torun- Working Group 《International Journal of Earth Sciences》2008,97(2):307-315

High-precision temperature measurements were carried out up to a depth of 2,930 m in the 5.5-km-deep well Torun-1, 26 years after completion of drilling. The temperature log provides equilibrium thermal state information for the Polish Lowland at the western margin of the Precambrian craton. Geothermal gradient calculated from the equilibrium temperature log, together with estimates of thermal conductivity from ‘net rock’ geophysical well logging analysis and available core measurements, yields heat flow in the range 50–60 mW/m² below 2-km depth. Heat flow of 50 mW/m² plus ∼10 mW/m² generated within thick sediments and highly metamorphosed sedimentary wedge is typical for the western margin of the Precambrian East European craton. Heat-flow variations with depth can be explained by a model of surface-temperature changes >10°C (glaciation to Holocene). Torun-1 Working Group: Marta Wróblewska, Jacek Majorowicz, Jan Szewczyk, Jan Šafanda, Vladimír Cermák  相似文献   

Bridging High School and Introductory Undergraduate Courses in Geographic Information Science and Technology     

AP® GIS&T Study Group 《The Journal of geography》2018,117(4):165-173

This article presents the findings of a study to determine the degree of consistency in what is taught and learned in high school and college-level introductory courses in geographic information science and technology (GIS&T). A content analysis identified sixteen topics that are generally representative of the knowledge, skills, and abilities developed in introductory undergraduate courses. The findings were used to propose a standard college-level survey course in GIS&T that could inform future efforts to introduce more academically rigorous GIS&T coursework in high schools, such as through the Advanced Placement Program.  相似文献   

Last deglaciation and Holocene environmental change at high altitude in the Pyrenees: the geochemical and paleomagnetic record from Marboré Lake (N Spain)     

B. Oliva-Urcia  A. Moreno  M. Leunda  B. Valero-Garcés  P. González-Sampériz  G. Gil-Romera  M. P. Mata  HORDA Group 《Journal of Paleolimnology》2018,59(3):349-371

Sedimentological, geochemical and magnetic data in a ~ 7-m sequence from Marboré Lake (2612 m asl, central Pyrenees) provide information about environmental variability since the last glacier retreat (14.6 cal ka BP) in high-altitude Pyrenean environments. The sediment sequence is composed of millimeter- to centimeter-thick rhythmites made of finer greyish laminae and coarser-grain, carbonate-bearing laminae arranged in varied patterns throughout the sequence. Finer laminae are interpreted as deposition during periods of predominantly ice-covered conditions, whereas coarser, carbonate-bearing sediments reflect periods of higher runoff. The age model, based on 13 ¹⁴C dates and a reservoir effect assessed with ²¹⁰Pb and ¹³⁷Cs, is coherent with known synchronous vegetation changes across the Pyrenees. Warmer intervals such as GI-1 (14.6–12.8 cal ka BP, Bølling/Allerød period), 10.4–8.2 cal ka BP in the Early Holocene, 7.5–5.2 cal ka BP in the Mid Holocene and the Medieval Climate Anomaly (AD 900–1300), are characterized by peaks in productivity and higher carbonate preservation. Deposition during colder periods such as GS-1 (12.8–11.7 cal ka BP), the Neoglacial (ca. 5.2–3.5 cal ka BP) and the Little Ice Age (last 400 years) show an increase in finer laminae. The presence of magnetite throughout the whole section suggests that Marboré Lake maintained predominantly oxic conditions since its formation. Changes in magnetic properties and the increase in magnetite from 3.5 cal ka BP to present, however, indicate a more oxic environment at the lake bottom during the last few millennia. The occurrence of Pb concentration peaks in sediments of Roman and modern age demonstrates the global distribution of heavy metal deposition, even into high-mountain lakes.  相似文献   

Shear wave splitting in the Eastern Alps observed at the TRANSALP network     

Jrn Kummerow  Rainer Kind  TRANSALP Working Group 《Tectonophysics》2006,414(1-4):117

Data from the temporary TRANSALP seismic network were analysed to investigate the seismic anisotropy in the upper mantle beneath the Eastern Alps. We operated mostly short period and some broadband stations in a dense linear array, which transects the Eastern Alps at 12° E longitude. Recorded SKS and SKKS phases with different backazimuths were used simultaneously to calculate the splitting parameters of delay time and fast axis direction for each seismic station. While we found variations in the delay times between 0.8 and 2.0 s, the determined fast axis directions prove to be rather consistent along the profile (60°–70° N). They coincide well with the trend of the Eastern Alps, thus suggesting orogen-parallel flow in the upper mantle. Our findings support the earlier proposed idea that the Adriatic indenter which was forced northwards into the European plate during the late stage of the Alpine orogeny, triggered an escape movement to the less constrained Pannonian basin to the east.  相似文献   

Geological characterization of the Prestige sinking area     

Ercilla G  Córdoba D  Gallart J  Gràcia E  Muñoz JA  Somoza L  Vázquez JT  Vilas F;Prestige Group 《Marine pollution bulletin》2006,53(5-7):208-219

The tanker Prestige sank off NW Iberia on the 19th November 2002. The stern and bow of the Prestige wreck are located on the southwestern edge of the Galicia Bank, at 3565 m and 3830 m water depths, respectively. This bank is a structural high controlled by major faults with predominant N-S, NNE-SSW, and NNW-SEE trends. It is characterized by moderate to low seismic activity. The faults have controlled the local depositional architecture, deforming, fracturing, relocating and distributing sediments since the Valangian (early Cretaceous). The Prestige sinking area corresponds to an asymmetric half-graben structure with a N-S trend, which conditions the present-day morphology. The faulted flank outcrops and its activity and erosion have favoured the occurrence of mass-movements (slumps, slump debris, mass-flows and turbidity currents), building valleys and depositional lobes. Nearsurface sediments comprise mostly terrigenous and biogenous turbiditic muds and sands with a minor presence of hemipelagic muds, except on the fault scarp where pelagites predominate. Potential geological hazards resulting from tectonic and sedimentary processes affect almost the entire Prestige sinking area.  相似文献   

基于熵值-理想点法的泥石流危险度研究     

刘朝安  高文龙  阙金声  陈剑平 《吉林大学学报(地球科学版)》2011,(Z1):201-206,226

泥石流危险度的划分是泥石流研究中的重点与难点,泥石流危险度的确定对于泥石流整体特征的把握具有十分重要的作用。采用熵值-理想点法建立了泥石流危险度划分模型,选取流域面积、主沟长度与泥石流沟相对最大高差等10个评价指标。利用现场3条泥石流沟作为工程评价对象,通过熵值法确定各评价指标的权重系数,并采用理想点法进行泥石流危险度的划分研究。根据模型分析结果,泥石流沟2与3属于高危险度(贴近度为0.79与0.83),泥石流沟1属于中危险度(贴近度为0.82)。泥石流危险度与现场情况及已有研究资料基本一致,证明了该法在泥石流危险度划分中的合理性与有效性。  相似文献   

Report of the Science Community Workshop on the proposed First Sample Depot for the Mars Sample Return Campaign     

Prepared by the MSR Campaign Science Group  A. D. Czaja  M.-P. Zorzano  the rest of the MCSG team  with Chairs  G. Kminek  M. A. Meyer  Members  D. W. Beaty  E. Sefton-Nash  B. L. Carrier  F. Thiessen  T. Haltigin  A. Bouvier  N. Dauphas  K. L. French  L. J. Hallis  R. L. Harris  E. Hauber  L. E. Rodriguez  S. P. Schwenzer  A. Steele  K. T. Tait  M. T. Thorpe  T. Usui  J. Vanhomwegen  M. A. Velbel  S. Edwin  K. A. Farley  D. P. Glavin  A. D. Harrington  L. E. Hays  A. Hutzler  M. Wadhwa 《Meteoritics & planetary science》2023,58(6):885-896

The Mars 2020/Mars Sample Return (MSR) Sample Depot Science Community Workshop was held on September 28 and 30, 2022, to assess the Scientifically-Return Worthy (SRW) value of the full collection of samples acquired by the rover Perseverance at Jezero Crater, and of a proposed subset of samples to be left as a First Depot at a location within Jezero Crater called Three Forks. The primary outcome of the workshop was that the community is in consensus on the following statement: The proposed set of ten sample tubes that includes seven rock samples, one regolith sample, one atmospheric sample, and one witness tube constitutes a SRW collection that: (1) represents the diversity of the explored region around the landing site, (2) covers partially or fully, in a balanced way, all of the International MSR Objectives and Samples Team scientific objectives that are applicable to Jezero Crater, and (3) the analyses of samples in this First Depot on Earth would be of fundamental importance, providing a substantial improvement in our understanding of Mars. At the conclusion of the meeting, there was overall community support for forming the First Depot as described at the workshop and placing it at the Three Forks site. The community also recognized that the diversity of the Rover Cache (the sample collection that remains on the rover after placing the First Depot) will significantly improve with the samples that are planned to be obtained in the future by the Perseverance rover and that the Rover Cache is the primary target for MSR to return to Earth.  相似文献