HR: 16:00h
AN: GP24A-01 INVITED     [Abstracts]
TI: A Novel Database to Rank and Display Archeomagnetic Intensity Data
AU: * Donadini, F
EM: fabio.donadini@helsinki.fi
AF: Division of Geophysics, University of Helsinki, Gustav Hällströmin katu 2 P.O. Box 64, Helsinki, 00014 Finland
AU: Korhonen, K
EM: kimmo.korhonen@hut.fi
AF: Laboratory of Geoenvironmental Technology, Helsinki University of Technology, Otakaari 1, P.O. Box 1000, Espoo, 02015 Finland
AU: Riisager, P
EM: pri@snm.ku.dk
AF: GeoBiosphere Science Centre, University of Lund, Sölvegatan 12, Lund, 22362 Sweden
AU: Pesonen, L J
EM: lauri.pesonen@helsinki.fi
AF: Division of Geophysics, University of Helsinki, Gustav Hällströmin katu 2 P.O. Box 64, Helsinki, 00014 Finland
AU: Kahma, K
EM: kimmo.kahma@fimr.fi
AF: Finnish Institute of Marine Research, Lyypekinkuja 3 A, P.O. Box 33, Helsinki, 00931 Finland
AB: To understand the content and the causes of the changes in the Earth's magnetic field beyond the observatory records one has to rely on archeomagnetic and lake sediment paleomagnetic data. The regional archeointensity curves are often of different quality and temporally variable which hampers the global analysis of the data in terms of dipole vs non-dipole field. We have developed a novel archeointensity database application utilizing MySQL, PHP (PHP Hypertext Preprocessor), and the Generic Mapping Tools (GMT) for ranking and displaying geomagnetic intensity data from the last 12000 years. Our application has the advantage that no specific software is required to query the database and view the results. Querying the database is performed using any Web browser; a fill-out form is used to enter the site location and a minimum ranking value to select the data points to be displayed. The form also features the possibility to select plotting of the data as an archeointensity curve with error bars, and a Virtual Axial Dipole Moment (VADM) or ancient field value (B_a) curve calculated using the CALS7K model (Continuous Archaeomagnetic and Lake Sediment geomagnetic model) of (Korte and Constable, 2005). The results of a query are displayed on a Web page containing a table summarizing the query parameters, a table showing the archeointensity values satisfying the query parameters, and a plot of VADM or B_a as a function of sample age. The database consists of eight related tables. The main one, INTENSITIES, stores the 3704 archeointensity measurements collected from 159 publications as VADM (and VDM when available) and B_a values, including their standard deviations and sampling locations. It also contains the number of samples and specimens measured from each site. The REFS table stores the references to a particular study. The names, latitudes, and longitudes of the regions where the samples were collected are stored in the SITES table. The MATERIALS, METHODS, SPECIMEN_TYPES and DATING_METHODS tables store information about the sample materials, intensity determination methods, specimen types and age determination methods. The SIGMA_COUNT table is used indirectly for ranking data according to the number of samples measured and their standard deviations. Each intensity measurement is assigned a score (0--2) depending on the number of specimens measured and their standard deviations, the intensity determination method, the type of specimens measured and materials. The ranking of each data point is calculated as the sum of the four scores and varies between 0 and 8. Additionally, users can select the parameters that will be included in the ranking.
DE: 1503 Archeomagnetism
DE: 1521 Paleointensity
DE: 1560 Time variations: secular and longer
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005