Kimmo Korhonen

GEOMAGIA50.v3: 1. general structure and modifications to the archeological and volcanic database

BackgroundGEOMAGIA50.v3 is a comprehensive online database providing access to published paleomagnetic, rock magnetic, and chronological data from a variety of materials that record Earth’s magnetic field over the past 50 ka.FindingsSince its original release in 2006, the structure and function of the database have been updated and a significant number of data have been added. Notable modifications are the following: (1) the inclusion of additional intensity, directional and metadata from archeological and volcanic materials and an improved documentation of radiocarbon dates; (2) a new data model to accommodate paleomagnetic, rock magnetic, and chronological data from lake and marine sediments; (3) a refinement of the geographic constraints in the archeomagnetic/volcanic query allowing selection of particular locations; (4) more flexible methodological and statistical constraints in the archeomagnetic/volcanic query; (5) the calculation of predictions of the Holocene geomagnetic field from a series of time varying global field models; (6) searchable reference lists; and (7) an updated web interface. This paper describes general modifications to the database and specific aspects of the archeomagnetic and volcanic database. The reader is referred to a companion publication for a description of the sediment database.ConclusionsThe archeomagnetic and volcanic part of GEOMAGIA50.v3 currently contains 14,645 data (declination, inclination, and paleointensity) from 461 studies published between 1959 and 2014. We review the paleomagnetic methods used to obtain these data and discuss applications of the data within the database. The database continues to expand as legacy data are added and new studies published. The web-based interface can be found at http://geomagia.gfz-potsdam.de.

GEOMAGIA50.v3: 2. A new paleomagnetic database for lake and marine sediments

BackgroundGEOMAGIA50.v3 for sediments is a comprehensive online database providing access to published paleomagnetic, rock magnetic, and chronological data obtained from lake and marine sediments deposited over the past 50 ka. Its objective is to catalogue data that will improve our understanding of changes in the geomagnetic field, physical environments, and climate.FindingsGEOMAGIA50.v3 for sediments builds upon the structure of the pre-existing GEOMAGIA50 database for magnetic data from archeological and volcanic materials. A strong emphasis has been placed on the storage of geochronological data, and it is the first magnetic archive that includes comprehensive radiocarbon age data from sediments. The database will be updated as new sediment data become available.ConclusionsThe web-based interface for the sediment database is located at http://geomagia.gfz-potsdam.de/geomagiav3/SDquery.php. This paper is a companion to Brown et al. (Earth Planets Space doi:10.1186/s40623-015-0232-0, 2015) and describes the data types, structure, and functionality of the sediment database.

Hydrogeological Effects on Superconducting Gravimeter Measurements at Metsähovi in Finland

The purpose of this study is to gain a better knowledge of superconducting gravimeter (SG) data at the Metsahovi Gravity station in Southern Finland. Because SG data have a high precision (1ngal) and are very sensitive to various environmental effects, we must isolate and analyze the characteristics of these effects before we are able to consider their effects in data. As a result of extensive studies we have isolated four hydrogeological sources influencing the gravity field at the Metsahovi site. The first one, the time-varying amount of surface and soil water close to the station causes an immediate effect on gravity after rains. The second source, the water flow in the fractures of crystalline bedrock above the groundwater table below the station can be observed soon after rains. The third one, the porosity variation of the bedrock within the range of groundwater level variation is a long-term effect, which influence on the gravity field can vary over a wide range. The last source, the flow rate diffe...