Options
Zlotnicki, J.
Loading...
Preferred name
Zlotnicki, J.
6 results
Now showing 1 - 6 of 6
- PublicationOpen AccessDrag-out effect of piezomagnetic signals due to a borehole: the Mogi source as an example(2007-02)
; ; ; ; ; ; ; ; ; ; ;Sasai, Y.; Disaster Prevention Division, Bureau of General Affairs, Tokyo Metropolitan Government, Tokyo, Japan ;Johnston, M. J. S.; US Geological Survey, Menlo Park, CA, U.S.A. ;Tanaka, Y.; Graduate School of Science, Kyoto University, Japan ;Mueller, R.; US Geological Survey, Menlo Park, CA, U.S.A. ;Hashimoto, T.; Graduate School of Science, Hokkaido University, Japan ;Utsugi, M.; Graduate School of Science, Kyoto University, Japan ;Sakanaka, S.; Faculty of Engineering and Resource Science, Akita University, Japan ;Uyeshima, M.; Earthquake Research Institute, The University of Tokyo, Japan ;Zlotnicki, J.; Observatoire de Physique du Globe de Clermont-Ferrand, France ;Yvetot, P.; Observatoire de Physique du Globe de Clermont-Ferrand, France; ; ; ; ; ; ; ; ; We show that using borehole measurements in tectonomagnetic experiments allows enhancement of the observed signals. New magnetic dipoles, which vary with stress changes from mechanical sources, are produced on the walls of the borehole. We evaluate such an effect quantitatively. First we formulate a general expression for the borehole effect due to any arbitrary source models. This is valid everywhere above the ground surface as well as within the cylindrical hole. A first-order approximate solution is given by a line of horizontal dipoles and vertical quadrupoles along the central axis of the borehole, which is valid above the ground surface and a slightly away (several tens of cm) from the top of the borehole. Selecting the Mogi model as an example, we numerically evaluated the borehole effect. It turned out that the vertical quadrupoles produce two orders of magnitude more intense magnetic field than the horizontal dipoles. The borehole effect is very local, i.e. detectable only within a few m from its outlet, since it is of the same order or more than the case without a borehole. However, magnetic lines of force cannot reach the ground surface from a deeper portion (>10 m) of a borehole.127 162 - PublicationOpen AccessDiscussion on telluric field and seismic activity in Central Greece(2000-06)
; ; ; ;Vargemezis, G.; Geophysical Laboratory of Thessaloniki, Greece ;Tsokas, G. N.; Geophysical Laboratory of Thessaloniki, Greece ;Zlotnicki, J.; Laboratoire Geophysique d'Orleans (LGO-CNRS), Orleans, France; ; Two stations were installed in the Southeastern Thessaly basin (Central Greece), recording the geomagnetic and telluric fields from 1993 to 1996. The aim was to detect long-term abnormal changes of the telluric field, which were possibly related to imbedding earthquakes. Between January 1993 and October 1996, 213 and185 (Neraida and Mavrolofos stations respectively) abnormal changes of the telluric field were observed in association with the seismic activity. The duration of these changes varied from several minutes to 24 days and the maximum amplitude was 3.8 mV/m. Data recording detected 625 and 917 seismic events for Neraida and Mavrolofos station respectively. The percentage of the earthquakes associated with the telluric anomalies is 27% and 16% respectively for each station. Both percentages are considered to be very low. Telluric activity was followed by a burst of seismic activity in areas spreading to different directions from the stations. A correlation of the characteristics of the telluric field with the earthquake magnitude was attempted, but no reliable relationship was obtained.115 450 - PublicationOpen AccessMonitoring of the geomagnetic and geoelectric field in two regions of Greece for the detection of earthquake precursors(1997-03)
; ; ; ; ; ;Vargemezis, G.; Geophysical Laboratory, University of Thessaloniki, Greece ;Zlotnicki, J.; Laboratoire de Geophysique d'Orleans, France ;Tsokas, G.; Geophysical Laboratory, University of Thessaloniki, Greece ;Papazachos, B. C.; Geophysical Laboratory, University of Thessaloniki, Greece ;Papadimitriou, E. E.; Geophysical Laboratory, University of Thessaloniki, Greece; ; ; ; Two magnetotelluric stations have been installed in the South-Eastern Thessaly basin (Central Greece), which have recorded the geomagnetic and geoelectric fields since 1993. The aim is to detect long lasting abnormal changes of the geoelectric field which may be due to impending earthquakes. The geoelectric recordings were checked against the climatic changes such as temperature changes and precipitation and no correlation was observed. Ten anomalies were observed with characteristics similar to seismoelectric signals which have been reported in the literature and thus we can assume that these changes constitute precursory phenomena. The duration of these signals varies from several days to a few weeks. Some of them keep on developing until the occurrence of an earthquake, and others appear like transient changes several days before. The high seismicity of the area where the stations are located creates difficulties in the correlation of the signals with certain shocks.155 141 - PublicationOpen AccessSelf-potential chenges associated with volcanic activity: Short-term signals associated with March 9, 1998 eruption on La Fournaise volcano (Reunion Island)(2001-04)
; ; ; ; ; ;Zlotnicki, J.; UMR6530, Clermont-Ferrand, France ;Le mouel, J. L.; Laboratoire de GéomagnèTisme, IPGP, Paris, France ;Sasai, Y.; Earthquake Research Institute, University of Tokyo, Japan ;Yvetot, P.; UMR6524, Laboratoire de Geophysique d'Orleans, France ;Ardisson, M. H.; UMR6524, Laboratoire de Geophysique d'Orleans, France; ; ; ; After six years of quietness La Fournaise volcano entered into activity on March 9, 1998. Fissures opened gradually downwards on the northern flank of the cone. Two cones, Kapor and Krafft built, from which lava poured until September 1998. Several other vents opened during this eruption. Mappings, surveys, and continuous recordings of the Self-Potential have been performed on the volcano for twenty years. SP mappings disclose the variability of large scale SP anomalies due to the modification of the hydrothermal system over some ten years. Most of the eruptions take place along a Main Fracture Zone (MFZ) in which ground water flows prevail. SP measurements have also regularly been made on the northern flank of the cone, on a west-east profile crossing the MFZ. Between 1981 and 1992 an enlargement and a shift of the MFZ to the east are evidenced. In particular, the eastern fissural axis trending N35°E could be related to the possible collapse of the east flank of the volcano. After a decrease between 1992 and 1997, the SP anomaly was enhanced again by the 1998 eruption. Short scale, about 250 m wide, 750 mV amplitude anomalies were superimposed on a large scale one, 2500 m wide, and about 250 mV in amplitude. For several years, continuous stations have been measuring the electric field along two directions, with a 20 s sampling, in order to record the genesis of SP signals associated with the volcanic activity. Oscillations belonging to the ULF band were evidenced several days before the 1988 eruption, some of them at 9 km from the summit. Their amplitude reached several tens mV/km. These oscillations sometimes present a phase lag from one station to another; they progressively shift towards the location of the future effusive vents. The polarisation of the oscillations is similar to the polarisation of longer SP variations (1 h period or more) and are correlated with the structural anisotropy. Finally, during the last hours preceding the effusive activity, huge SP signals, up to a few Volts/km, appeared at the stations located on the MFZ, and especially on the branch where the magma migrated. We interpret these SP signals as due to electrokinetic effects generated by fluid flow in cracks opened by the stress field changes.153 248 - PublicationOpen AccessEvaluation of electric and magnetic field monitoring of Miyake-jima volcano monitoring of Miyake-jima volcanomonitoring of Miyake-jima volcano (Central Japan): 1995-1999(2001-04)
; ; ; ; ; ; ; ; ;Sasai, Y.; Earthquake Research Institute, University of Tokyo, Japan ;Zlotnicki, J.; Observatoire de Physique du globe de Clermont-Ferrand, Universitè Blaise Pascal et UMR6524, Aubiére cedex, France ;Nishida, Y.; Graduate school of science, Hokkaiodo University, Sappoto, Japan ;Uyeshima, M.; Earthquake Research Institute, University of Tokyo, Japan ;Yvetot, P.; Observatoire de Physique du globe de Clermont-Ferrand, Universitè Blaise Pascal et UMR6524, Aubiére cedex, France ;Tanaka, Y.; Volcano Research Center; Graduate Schoool of science, Kyoto University, Aso, Kumamoto, Japan ;Watanabe, H.; Earthquake Research Institute, University of Tokyo, Japan ;Takahashi, Y.; Earthquake Research Institute, University of Tokyo, Japan; ; ; ; ; ; ; full abstract in pdf130 452 - PublicationOpen AccessEnergy and polarization of the telluric field in correlation with seismic activity in Greece(2001-04)
; ; ; ;Vargemezis, G.; Geophysical Laboratory of Thessaloniki, Greece ;Zlotnicki, J.; Observatoire de Physique du Globe de Clermont-Ferrand, UMR6524, France ;Tsokas, G. N.; Geophysical Laboratory of Thessaloniki, Greece; ; Many attempts have been made to disclose anomalous changes of the electromagnetic field in relation with tectonic earthquakes. We tentatively develop a new approach based on the energy and polarity of the electric field, and apply this method to the seismicity in Greece. The study of the parameters of the horizontal electric field is realized in a time interval of five years. The data set allows the study of long-term variations of the field. Further, we examined the possible relation of the geoelectric activity with long distance seismicity (up to 500 km). The energy of the electric signal was estimated and correlated with the logarithm of the seismic moment (M 0 ). The values of the seismic moment estimated for each earthquake were summed for daily intervals, and the logarithm of the sum was computed. The same process was applied to the energy of the geoelectric field. Then, a correlation was attempted between the energy of the geoelectric field and the seismic moment referring to daily intervals. In two cases, changes in the energy of the horizontal geoelectric field were observed before the burst of the seismic activity. The energy of the telluric field increased several months before the burst of seismic activity and recovered right after the occurrence of the mainshocks. The hodograms of the horizontal geoelectric field show polarization changes regardless of the magnetic field. This is possibly attributed to the process of generation of electric currents before major earthquakes. Due to high and continuous regional seismicity in Greece, it was impossible to attribute the response of the polarization to the activation of specific seismic areas. It seems that the long-term energy variations of the horizontal geoelectric field as well as the polarization are related to forthcoming seismic activity. Therefore, long-term energy variations of the horizontal geoelectric field as well as the polarization could be used in tandem with other possible precursors in order to contribute to earthquake prediction studies.296 757