Summary and Suggestions for the VAN measurements for Japan
P. Varotsos (University of Athens)
Short Description of Measurements
At a depth of 2m electrodes are buried at distances betwen 50m and 10km or so. The combination of short and long dipoles is absolutely necessary for the discrimination of true Seismic Electric Signals (SES) and artificial noise. The doubts expressed by non-experts in the past that VAN group measures noise have no basis as this way of eliminating the noise has been approved by an International Conference held at Lake arrowhead (California, June 1992 organized by National Science Foundation). In this conference, the USA expert an electrical measurements expressed their favorable opinion which was later (in 1993) published in Review of Geophysics.
Most of the VAN stations are installed in Army stations (soldiers having scientific background take care of our stations after the official agreement of the Ministry of National Defense).
The data (1 measurement per channel per second) are transmitted to a central station in Athenes through open telephone lines. After the recent 6.6 EQ on May 13, 1995 in Greece the Minister of Public Works officially announced that telephone line free of charge will be given to the group.
Total Results since Jan. 1, 1987 until present
13 earthquakes occurred with Ms(ATH)>=5.8 (i.e. Mb(USGS)=5.2 or 5.3). Three earthquakes were missed, one earthquake was unsuccessfully predicted, nine earthquakes ware successfully predicted.
a) A 6.0 earthquake occurred on May 4, 1995 30km ESE of Tessaloniki. The VAN prediction was issued on April 7 expecting a 5.8 earthquake at the area at which the earthquake actually occurred. The Greek Government officially confirmed the success of the prediction and also announced that measurements ware taken at the area at which the earthquake actually occureed.
b) A 6.6 earthquake occurred on May 13, 1995 in Northern Greece (epicenter at 40.0゜N, 21.6゜E) at the area which was previously considered to be aseismic (for more than 1000 years no such earthquakes had occured there). The final prediction was issued on April 30, 1995 and started an expected 6.0 earthquake close to Ioannina station which lies only 70km from the epicenter. This prediction was addressed to the Greek authorities, to 29 international institutes as well as the Royal Society (because a meeting for the VAN critical evaluation was going to be held on May 11 and 12).
Suggestions for Japan
(1) Immediate installation of the VAN network coordinated by the same group of Prof. Uyeda (in order to find the sensitive points).
(2) Immediate need of personal experienced in such type of measurements and dedicated for it.
(3) The arguments that high noise exists in Japan does not hold because recent experiments by the group of Prof. Uyeda showed noise level compatible to that in Greece.