Iaga Paleomagnetic Databases with access

Since the release of the Global Paleomagnetic Database (GPMDB) in 1991, there have been successive updates every two years, with the current version being 3.1. The authors have now constructed a set of four databases that have been sponsored by the International Association of Geomagnetism and Aeronomy (IAGA). These include the GPMDB together with the Paleointensity Database (PALIN), the Polarity Transitions Database (TRANS) and the Secular Variation Database (SECVR). Each of these databases is now released to operate under Microsoft Access V2.0 and are specifically designed so as to operate independently of each other. The design and operation of these databases with Access is described in this second supplement to the Global Paleomagnetic Databases.     

WATEQB – BASICA REVISION OF WATEQF FOR IBM PERSONAL COMPUTERS

Abstract. WATEQB is a BASICA revision for IBM PC of WATEQF, a geochemical model for chemical equilibrium and saturation of natural waters. This model computes the speciation of inorganic ions and complex species in solution for a given water analysis.
WATEQB is identical to the FORTRAN IV version from the standpoint of chemical process; however, the structure of the program differs from the original version. The structure of the program is not complex and allows the user to try some new modifications, if necessary.
Due to the limited memory of personal computers and in contrast to the large volume of the original version of the program, the author has created four data files, one of which is of random access type. Reading the thermochemical data is possible through these four data files.
This paper demonstrates how to set up the input data to execute WATEQB and describes the program rather than the model. The users of WATEQB will increase as personal computers become more common.     

Harmonization check of M w within the central, northern, and northwestern European earthquake catalogue (CENEC)

Large data sets covering large areas and time spans and composed of many different independent sources raise the question of the obtained degree of harmonization. The present study is an analysis of the harmonization with respect to the moment magnitude M _w within the earthquake catalogue for central, northern, and northwestern Europe (CENEC). The CENEC earthquake catalogue (Grünthal et al., J Seismol, 2009) contains parameters for over 8,000 events in the time period 1000–2004 with magnitude M _w ≥ 3.5. Only about 2% of the data used for CENEC have original M _w magnitudes derived directly from digital data. Some of the local catalogues and data files providing data give M _w, but calculated by the respective agency from other magnitude measures or intensity. About 60% of the local data give strength measures other than M _w, and these have to be transformed by us using available formulae or new regressions based on original M _w data. Although all events are thus unified to M _w magnitude, inhomogeneity in the M _w obtained from over 40 local catalogues and data files and 50 special studies is inevitable. Two different approaches have been followed to investigate the compatibility of the different M _w sets throughout CENEC. The first harmonization check is performed using M _w from moment tensor solutions from SMTS and Pondrelli et al. (Phys Earth Planet Inter 130:71–101, 2002; Phys Earth Planet Inter 164:90–112, 2007). The method to derive the SMTS is described, e.g., by Braunmiller et al. (Tectonophysics 356:5–22, 2002) and Bernardi et al. (Geophys J Int 157:703–716, 2004), and the data are available in greater extent since 1997. One check is made against the M _w given in national catalogues and another against the M _w derived by applying different empirical relations developed for CENEC. The second harmonization check concerns the vast majority of data in CENEC related to earthquakes prior to 1997 or where no moment tensor based M _w exists. In this case, an empirical relation for the M _w dependence on epicentral intensity (I ₀) and focal depth (h) was derived for 41 master events, i.e., earthquakes, located all over central Europe, with high-quality data. To include also the data lacking h, the corresponding depth-independent relation for these 41 events was also derived. These equations are compared with the different sets of data from which CENEC has been composed, and the goodness of fit is demonstrated for each set. The vast majority of the events are very well or reasonably consistent with the respective relation so that the data can be said to be harmonized with respect to M _w, but there are exceptions, which are discussed in detail.     

The Evolution of the Eastern Part of the Terek Mouth Area in the Period of the Caspian Sea Level Rise: Mapping Based on Aerospace Materials

The evolution of the eastern part of the Terek mouth area in the period of the current rise of the Caspian Sea level has been traced by aerial and space photographs made at different times. With the help of computer processing of the photographs, a set of maps have been compiled including maps of the eastern part of the Terek delta (including the former Agrakhan Bay and the Agrakhan Peninsula with a new delta) in 1978, 1991, and 1997, as well as a map of its dynamics in the period of its most radical changes (1978–1991). The response of the coastal environment to the sea level rise has been analyzed, and the correctness of the forecasts of changes in the coastal zone has been evaluated.     

Operational predictability of winter blocking at ECMWF: an update

Seven winters of analyses and forecasts from the operational archives of the European Centre for Medium Range Weather Forecast had been previously analyzed to assess the performance of the model in forecasting blocking events. This work updates some of this previous diagnostic work to the last five winters, from 1987/88 to 1991/92. The data set therefore covers all winter seasons (DJF) from 1980/81 to 1991/92, and consists of daily northern hemisphere 500 hPa geopotential height analyses and of the ten corresponding forecasts verifying on the same day (“Lorenz data”). Local blocking and sector blocking have been defined, using different modifications of the original Lejenas and Økland index. The comparison between the first seven and the last five winters, within the restrictions imposed by limited length of the data set, suggests a much improved situation as far as model climatology of blocking is concerned, especially over the Euro-Atlantic region. Operational predictability of blocking as an initial value problem is also shown to be measurably improved, in both Atlantic and Pacific sectors. All such improvements are shown to have taken place together with a considerable reduction of the model systematic error. Nevertheless, forecasting blocking in the medium range remains a difficult task for the model. More work is needed to understand whether the improvements are to be ascribed to the increased model resolution or to better physical parametrisations.     

基于Matlab的强震数据处理技术实现

强震动观测数据通常由强震仪原始二进制加速度记录组成,在国内外相关强震数据库下载的强震记录均为解码、处理后的ASCII格式文本文件,非原始文件,记录格式不同,但均由数据头段和数据区2部分组成。以我国未校正加速度记录(UA)数据格式为例,探讨基于Matlab程序的强震数据处理技术,并识别记录的地震动特性,为强震数据多领域应用提供技术支持。     

PALEOMAGIA: A PHP/MYSQL database of the Precambrian paleomagnetic data

Most paleomagnetic applications require a precise, rationally organized and up-todate catalogue or database of paleomagnetic results worldwide. These include reconstructions of continents, calculations of the Apparent Polar Wander Paths (APWPs) or paleolatitude drift curves, testing the Geocentric Axial Dipole (GAD) model, studies of geomagnetic paleosecular variation or reversal asymmetries, comparison of coeval results obtained from different types of rocks, estimation of inclination shallowing in sedimentary rocks and understanding the delay in remanence acquisition caused by slow cooling in large intrusions. For this purpose, various databases, such as the Global Paleomagnetic Database (GPMDB), and the Magnetics Information Consortium Database (MagIC) have been generated. This paper presents a new relational database (PALEOMAGIA) where 3278 entries of Precambrian data have been split geographically, sorted according to age and rock types and ranked using a revised version of the Van der Voo grading scheme. The latest geochronologic information is included wherever available. Significant effort has been put to the retrieval and archiving of data published in the last decade, which are virtually nonexistent in GPMDB. Here we present the database and its browser-based user interface from a scientific and a technical point of view.     

Modelling the release to the Kara Sea of radioactive waste from the icebreaker Lenin: Version II

In progressing its work for the International Arctic Seas Assessment Project (IASAP), under the auspices of the International Atomic Energy Agency (IAEA), the Source Term Working Group has developed a FORTRAN model to predict a radiation release profile into the Kara Sea from reactor fuel and activated components of the nuclear icebreaker Lenin. The model accounts for the degradation of containment materials through corrosion and other mechanisms, and predicts annual release rates to 4500 years into the future. Version I of the model was developed as a spreadsheet program from the original data gathered by the Working Group and the results were published by Timms et al. (1994); revised information on the method of disposal necessitated a change to the program, which is presented in this paper as Version II. The model is being applied to other marine reactors dumped in the Kara Sea in a programme of work for the IASAP aimed at assessing the collective release profile from all significant dump sites in this region.     

Scattered Surface Wave Energy in the Seismic Coda

One of the many important contributions that Aki has made to seismology pertains to the origin of coda waves (Aki, 1969; Aki and Chouet, 1975). In this paper, I revisit Aki's original idea of the role of scattered surface waves in the seismic coda. Based on the radiative transfer theory, I developed a new set of scattered wave energy equations by including scattered surface waves and body wave to surface wave scattering conversions. The work is an extended study of Zeng et al. (1991), Zeng (1993) and Sato (1994a) on multiple isotropic-scattering, and may shed new insight into the seismic coda wave interpretation. The scattering equations are solved numerically by first discretizing the model at regular grids and then solving the linear integral equations iteratively. The results show that scattered wave energy can be well approximated by body-wave to body wave scattering at earlier arrival times and short distances. At long distances from the source, scattered surface waves dominate scattered body waves at surface stations. Since surface waves are 2-D propagating waves, their scattered energies should in theory follow a common decay curve. The observed common decay trends on seismic coda of local earthquake recordings particular at long lapse times suggest that perhaps later seismic codas are dominated by scattered surface waves. When efficient body wave to surface wave conversion mechanisms are present in the shallow crustal layers, such as soft sediment layers, the scattered surface waves dominate the seismic coda at even early arrival times for shallow sources and at later arrival times for deeper events.     

Adaptation of the SNOWMAP algorithm for snow mapping over eastern Canada using Landsat-TM imagery

Abstract

The snow mapping algorithm SNOWMAP was adapted to Landsat-TM data and to the context of eastern Canada. Six Landsat-5 TM scenes were used. It was found that the original version of SNOWMAP greatly underestimates snow cover extent. The modification made to the original algorithm, by cancelling the minimum threshold of 0.1 on the NDVI value, allows gaps to be filled in. In addition, a spatial correction procedure applied to the modified SNOWMAP algorithm results improves snow detection under coniferous forests. Based on a limited data set of ground-based observations (only 40 sites were available), the modified SNOWMAP seems to perform better in snow detection than the original version of the algorithm. An application case is presented in order to demonstrate the relevance of the modified SNOWMAP results as a high spatial-resolution reference for the validation of historical snow maps derived from medium spatial-resolution satellite data.

Citation Chokmani, K., Dever, K., Bernier, M., Gauthier, Y. & Paquet, L.-M. (2010) Adaptation of the SNOWMAP algorithm for snow mapping over eastern Canada using Landsat-TM imagery. Hydrol. Sci. J. 55(4), 649–660.     

VELOCITY SPECTRA AND THEIR USE IN STRATIGRAPHIC AND LITHOLOGIC DIFFERENTIATION*

Velocity Spectra which were originally developed for the optimum stacking of seismic data have been found to give considerable information concerning lithologic and stratigraphic changes in the geologic section. In the Gulf of Mexico shale sections and sand bodies have been recognized on the Velocity Spectra display, and in the Caribbean last year a first attempt was made to utilize Velocity Spectra information for the determination and mapping of lithology. Since that time, a new program has been developed which takes dip into account when computing the interval velocity. This program has been applied to a seismic section in the North Sea which has resulted in a geologic model derived from interval velocities which were found to be quite consistent. Such a model can be of great value in geological interpretation.     

Results of locating the IASPEI GT(0-5) reference events using the standard ISC procedures

The International Seismological Centre (ISC) is charged with production of the definitive global bulletin of seismic events, based on the most comprehensive set of parametric data collected from all over the world. Almost every event in the bulletin retains the original hypocentral solutions reported to the ISC by contributing agencies. In addition, where possible, the ISC computes its own solution, which is intended to be the most accurate where the data from several networks are used. It is because of the requirement for consistency of the bulletin over the years that the procedures used at the centre to compute hypocentres have remained rather conservative despite considerable advances made in the field of earthquake location.The ISC has developed and put into operation a new data management system. As a result, it is now possible to review and subsequently introduce more up-to-date methods of locating seismic events into the operations. The ISC Governing Council called for a workshop dedicated to location procedures, which was held during the 2005 IASPEI General Assembly in Santiago, Chile.To compare the accuracy of different location algorithms, a list of 156 reference events (IWREF) was selected prior to the workshop. The list includes geographically well distributed earthquakes and explosions with positions known with an accuracy of up to 5 km. It covers the period of 1954-2001 and includes all station readings and hypocentral solutions of different agencies available for these events in the ISC bulletin. Although the original ISC solutions are included, these may be different from the solution obtainable now due to changes in the ISC procedures over the years. This paper presents the results of relocation of these events using standard ISC location procedures as of 2005. These new ISC locations and analysis of their shifts with respect to reference locations present a benchmark for further improvement.     

The European-Mediterranean Earthquake Catalogue (EMEC) for the last millennium

The catalogue by Grünthal et al. (J Seismol 13:517?C541, 2009a) of earthquakes in central, northern, and north-western Europe with M _w????3.5 (CENEC) has been expanded to cover also southern Europe and the Mediterranean area. It has also been extended in time (1000?C2006). Due to the strongly increased seismicity in the new area, the threshold for events south of the latitude 44°N has here been set at M _w????4.0, keeping the lower threshold in the northern catalogue part. This part has been updated with data from new and revised national and regional catalogues. The new Euro-Mediterranean Earthquake Catalogue (EMEC) is based on data from some 80 domestic catalogues and data files and over 100 special studies. Available original M _w and M ₀ data have been introduced. The analysis largely followed the lines of the Grünthal et al. (J Seismol 13:517?C541, 2009a) study, i.e., fake and duplicate events were identified and removed, polygons were specified within each of which one or more of the catalogues or data files have validity, and existing magnitudes and intensities were converted to M _w. Algorithms to compute M _w are based on relations provided locally, or more commonly on those derived by Grünthal et al. (J Seismol 13:517?C541, 2009a) or in the present study. The homogeneity of EMEC with respect to M _w for the different constituents was investigated and improved where feasible. EMEC contains entries of some 45,000 earthquakes. For each event, the date, time, location (including focal depth if available), intensity I ₀ (if given in the original catalogue), magnitude M _w (with uncertainty when given), and source (catalogue or special study) are presented. Besides the main EMEC catalogue, large events before year 1000 in the SE part of the investigated area and fake events, respectively, are given in separate lists.     

b-Values of two tectonic parts in the circum-pacific belt

Two different data sets have been applied to compute theb-parameter of the magnitude-frequency relation for two different areas in the circum-Pacific belt. These areas are: a) South America, Middle America and Mexico, b) all the remaining island arcs of the circum-Pacific belt, starting from Alaska and the Aleutian islands and proceeding southeastwards. The first data set spreads over 77 years, while the second one covers a 90-year period. In both cases the results clearly showed that theb-values are lower in the first of the above-mentioned areas, while respectively higher in the second. This is due to the tectonic conditions in these areas as estimated during the present work.     

Asymmetry of geomagnetic polarity: Equatorial dipole,Pangaea, and the Earth’s core

The paper presents the results of analyzing the set of dual-polarity paleomagnetic results the Global Paleomagnetic Database (GPMDB). The dataset was expanded by the results from the Paleomagnetic Data Catalogue for the USSR and with new data published after 2005. Some results were rejected to avoid the influence of overprints of ancient and recent magnetization. Overall, 59 dual-polarity results for the lithospheric plates of Baltica, Laurentia, and Siberia with their immediate framing were selected for the analysis in the interval of ages 207–359 Ma. The new data confirmed the model of the paleomagnetic field, according to which the field contains a long-lived component corresponding to the equatorial dipole which is responsible for the non-antipodal paleomagnetic directions in the zones of normal and reverse polarity in sedimentary and volcanic rock sequences. Retaining its value of 5–8% of the central axial dipole, the equatorial dipole changed its polarity a few times during the interval 359–207 Ma. The northern poles of the dipole formed two antipodal groups on the Earth’s surface, which lie within or near the subduction zones on the periphery of the Pangaea Supercontinent. Such localization of the equatorial dipole is suggested to be related to the ascending branches of the mantle convection and to the topography of both boundaries of the outer Earth’s core.     

AUTOMATIC PICKING OF FIRST ARRIVALS AND PARAMETERIZATION OF TRAVELTIME CURVES*

One of the methods for studying the near-surface low-velocity zone and for subsequent determination of static corrections is the technique of employing first arrivals. During the past few years several computer algorithms, based on some simplifying assumptions, have been suggested for automatic determination of first arrivals. This paper suggests a new method for automatic picking of first arrivals, which works under quite general assumptions concerning the character of the data. The method is based on the use of correlation properties of signals and the application of a statistical criterion for the estimation of first arrivals time. A number of dimensionless parameters is used in the algorithm making it possible to regulate the level of reliability and the resolution of the picking procedure. The second stage of the algorithm is the parameterization of the traveltime curve, that is a division of the previously obtained t—x curve into separate rectilinear segments. The suggested algorithm of parameterization is based on an heuristic use of some properties of maximum likelihood estimates. This permits location of the breakpoints of the t—x curve and the estimation of the parameters of each rectilinear segment. A computer program has been written based on the picking and parameterization algorithm. This program has been tested on a large amount of field data and the results show that it works at least as well as the hand procedure.     

基于MapReduce的地震波形数据并行解压缩算法研究

近年来各省级地震台网SEED文件数据量急增。在数据处理过程中,利用原有的串行解压缩算法批量解压缩地震波形数据时存在操作繁琐、耗时较长的问题。本文引入了MapReduce并行编程模型,根据该编程模型思想结合原有串行解压缩算法,提出了一种并行解压缩地震波形数据的算法,并给出了算法的设计与实现。本文从正确性、运行效率以及可扩展性三个方面进行了对比实验,验证了使用并行算法解压缩数据的效率较高,并且能够一次实现批量地震波形数据的解压缩,且操作简单。     

Local magnitude revaluation for recent Italian earthquakes (1981–1996)

In the framework of a joint project of theItalian Gruppo Nazionale per la Difesadai Terremoti (GNDT) and the IstitutoNazionale di Geofisica (ING), devoted tothe reorganization of the Italianearthquake instrumental database from 1981to 1996, we approached the problem of thehomogeneous determination of localmagnitude in Italy. As a first step, webuilt a database of real Wood-Andersonamplitudes deduced from the available dataof the two instruments that were inoperation in Italy up to 1989 as well as ofsimulated Wood Anderson amplitudes computedby Very Broad Band recordings, availablesince 1990. The simultaneous computation ofthe attenuation function together with themagnitudes and the station residuals allowsus to verify that, for the Italian area,this function does not significantly differfrom the original one given by Richter. Inthe second step, the so obtained Mlmagnitudes are used as a reference data setto estimate a new empirical relation forthe duration magnitude Md using the unifiedphases database of the Italian NationalSeismic Network (RSNC) of ING and of themost important local seismic networksoperating in Italy. The same data set wasalso employed to calibrate magnitude Mabased on amplitudes coming from shortperiod vertical seismograms recorded by theRSNC automatic acquisition system. At lasta set of reasonable criteria to choose themost reliable among Ml, Md and Ma has beenformulated. The resulting set of magnitudesproved to be definitely better calibratedthan the one obtained by procedures in useat RSNC.     

Rediscussion on the seismic regime network

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