Magnetic anomaly around Marian Cove in King George Island, Antarctica

第2回極域科学シンポジウム/第31回極域地学シンポジウム 11月16日（水） 国立国語研究

Magnetic anomaly around Marian Cove in King George Island with bathymetric and topographic data into consideration

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月29日（木） 国立極地研究所 ３階ラウン

Regular meeting of presentation training for undergraduate and graduate students in the course of Applied Earth Science, Akita University

We have weekly meeting of introducing latest researches in the course of Applied Earth Sciences, department of Earth Science and Technology, faculty of Engineering and Resource Science, Akita University. Regular participants are students and university staff (professor, associate professor, assistant professor and technician) belonging to the laboratories in the Applied Earth Science course. So the attendant students are fourth grade of undergraduates and graduates. Students usually introduce latest paper in the field of geosciences published in specialized journals. University staff members introduce their own research or report their visits associated with research activities. Presentations are done on the front of the audience. We call the meeting as "Zasshikai" which literally means "journal meeting" in Japanese. The meeting is regularly held in the evening of Monday during the first and second semesters and very good training place of presentation especially for students. Here I intend to introduce the activity of this meeting

＜Original Papers＞An automatic analysis of the curve matching method for electric sounding under layered strata

The curve matching method has traditionally used for analysis of the resistivity method, which is so-called electric sounding, under layered strata. In the curve matching method, at first we plot observed values of apparent resistivity on a logarithmic coordinate tracing paper. Then we analyze the subsurface resistivity structure with comparing the observed curve with the theoretical one for two-layered strata. Although the linear filter method, which can calculate the theoretical curve easily and accurately, is more popular in late years, the curve matching method has an advantage of visualizing the analysis process. In this manuscript, an automatic analysis of the curve matching method for Wenner electrode configuration is introduced. In the program code, Marquardt method, one of the non-linear least square methods, is used to fit the theoretical curve with the observed one. The examples of applying the automatic analysis to practical data and its availability are shown as well as the flow chart of the method

Electric Soundings at Tegata-Yama

Electric soundings have been carried out anually at Tegata-Yama, Akita city, northeast of Japan. They are part of the class ‘Experiment of Applied Geophysics I’ opened in Akita University for third year students of geology and geophysics cource, Department of Earth Science and Technology, Faculty of Engineering and Resource Science. We have carried out vertical soundings using the Wenner electrode distribution at several sites these years. We assign students a report including construction of one-dimensional resistivity structure using the curve matching method based on the data aquired themselves. But we do not have comprehensive image of subsurface resistivity structure in consideration of the data aquired over years. We examine the data obtained resent years and show several representative results of the electric soundongs around the top of Tegata-Yama hill in this manuscript. We intend to use this summary of the results in order to help the progressive understanding of the subsurface structure of Tegata-Yama area in the future

Cooling Shape of Vents beneath Fumaroles at Kuju-Iwoyama Inferred from Geomagnetic Changes by Repeated Surveys

Geothermal changes in the subsurface volcanic and geothermal areas can be inferred from monitoring the geomagnetic changes. We installed several proton precession magnetometers for continuous observation and set up tens of observation sites for repeated survey in the geothermal area at Kuju-Iwoyama, Kyushu Island, Southwest of Japan, after the vapor eruption (phreatic explosion) event in October of 1995. So far, we carried out repeated surveys three times - in March to April of 1999, August to September of 1999, and December of 1999 to January of 2000 for more than 30 sites. Geomagnetic changes in the total force close to 40nT/year were observed at some observation sites during less than one year. The amounts of changes obtained by the repeated surveys were consistent with those obtained by the continuous observations.In this study we indicate that installing a number of sites for repeated survey made it possible to reveal the shape of cooling or heating bodies to some extent. An inclined and cone-shaped cooling body beneath major fumaroles is inferred at Kuju-Iwoyama

Aeromagnetic Survey at Iwate Volcano

We conducted the first aeromagnetic survey at Iwate volcano, northeast of Japan. Our initial and ultimate purpose is detection of geomagnetic changes by repeated aeromagnetic surveys. One cause of geomagnetic secular change is thermal effect due to magnetization changes by heat supply or dissipation. This effect is supposed to be most significant at active volcanic regions. The positioning techniques by satellite system such as GPS have promoted recent years. It becomes more applicable to geomagnetic changes, since such changes are very sensitive against the observed position. We have not carried out sufficient repeated aeromagnetic surveys yet. Iwate volcano, however, is appropriate field for detection of magnetic changes. We introduce the outline of our survey in order to be helpful to figure out the possible problem in the future study. In addition, we discuss at some extent about obtained magnetic anomalies with mainly topography and describe the obtained knowledge at present

1998 Seismic Exploration, ASO98, in ASO Volcano

A seismic exploration, ASO98, was conducted in Aso Volcano in central Kyushu, Japan. The purpose of this exploration was both to obtain the detailed seismic structures beneath the central cones and to detect the kinematic character of volcanic tremors of Aso Volcano. Six shot points with chemical explosions and a temporary network with 296 seismic stations were deployed over the central cones in a range of 10 km east-west by 9 km north-south. All explosions were completed on 26 November, 1998, and seismic records were successfully acquired at each of 290 stations. This paper reports on the details of ASO98, such as examples of acquired seismic traces for shots, locations of stations and shots, Final first arrival times, amplitude distributions, and examples of records acquired of volcanic tremors. These data are expected to provide much knowledge about volcanic seismology and about Aso Volcano. Further analyses will be described in forthcoming papers