| 摘要 |
<p>The device monitors the electrical field present in the earth, by means of at least two electrrodes buried in the earth. The electrodes are connected through a shielded lead to a differential amplifier (DA). followed by a filter (F), an amplifier with variable gain (AV), a triggering circuit (T) and an alarm organ (B). The circuitry of the device is dimensioned so as to detect preferentially pulses of less than a second duration and an intensity of 5 to 50 mV m between the electrodes, and or pulses with 1 to 30 minutes duration and an intensity of 40 to 400 mu V/m between the electrodes. These two kinds of pulses occur generally a few minutes or less, and 6 - 8 hours before an earthquake, respectively, so that the latter can be predicted with sufficient accuracy.</p> |
