| 摘要 |
A method and apparatus in which a capacitor (10) is disposed in direct contact with the earth (130), and a short voltage pulse is applied to the capacitor (10) to transmit a pulse of electromagnetic radiation having a broad frequen- cy band into the earth (130). In a preferred embodiment, a portion of the electromagnetic radiation that has propagat- ed through the subsurface (130a, 130b) is detected (20) and processed to image the subsurface. The size (L) of the trans- mitting capacitor (10) should be sufficiently small to satisfy the relation Re[kL] < 1, where k is the wavenumber in the earth formation of each frequency component of radiation transmitted into the earth. In a preferred embodiment, the voltage pulse applied to the transmitting capacitor (10) has frequency components in a broad band front below 1 MHz to above 100 MHz, and the only frequency components of the detected electromagnetic radiation that are processed to image the subsurface have frequency in the range from about 500 KHz to 25 MHz.
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