JPS6259273B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is mounted on a ship sailing on the sea, emits sound waves into the sea, receives and records reflected waves from the seabed and the stratum boundary surface under the seafloor, and explores the stratum structure under the seafloor. This relates to the improvement of submarine geological exploration equipment.

As shown in FIG. 1, a conventional submarine geological exploration device includes a transmitting section 31 (sound source 1, transmitting circuit 2) and a receiving section 32.
(wave receiver 3, preamplifier 4, handpass filter 5, recording amplifier circuit 6, gain control circuit 7, control pulse generation circuit 8) and recording section 33 (recording circuit 9, synchronization pulse generation circuit 10).

In operation, the transmitting circuit 2 is activated by a signal from the control pulse generator 8, and the sound source 1 is activated by its output, which emits sound waves toward the ocean floor. Reflected waves from the ocean floor or the geological boundary surface beneath the ocean floor are converted into electrical signals by a wave receiver 3, and then input to a recording circuit 9 via a preamplifier 4, a bandpass converter 5, and a recording amplification circuit 6. Incidentally, in order to suppress reverberation immediately after transmission, the gain of the preamplifier 4 is controlled by the output of a gain control circuit 7 activated by a signal from a control pulse generation circuit 8.

Conventional submarine geological exploration devices such as those described above transmit and receive signals using a single frequency, so it was necessary to select a model or change to a sound source with a different frequency depending on the exploration purpose. This is due to the propagation characteristics of sound waves, etc. If the sound source is in a high frequency range, exploration records with high stratum resolution can be obtained, but on the other hand, the attenuation in the strata is large, so the exploration depth becomes shallow. On the other hand, if a sound source in a low frequency range is used, the attenuation will be small and the exploration depth will be deeper, but the degree of stratum resolution will be lower due to the wavelength etc. For this reason, even if sound sources with different frequencies are used to record on the same recorder, records in the high-frequency range will overlap the submarine records in the low-frequency range, making it impossible to obtain highly resolved records. There are also methods using multiple submarine geological exploration devices with different frequencies, but the sound source of the geological exploration devices generally has not only a single frequency component but also a fairly wide transmission frequency range, and since the recorders are asynchronous, each Reflected sound waves and the like often interfere with each other and cause problems on each recording. For these reasons, in order to obtain exploration records with high resolution and deep exploration depth, methods have been used in which the same survey area is surveyed separately using devices with different frequencies, but both methods result in a decrease in the image quality of the exploration records. However, there were disadvantages such as an increase in the amount of work and an increase in exploration costs.

The present invention provides a submarine geological exploration device that maintains a high degree of stratum resolution and enables exploration deep beneath the seabed.

That is, the device according to the present invention includes a transmitter that emits a plurality of sound waves with different frequencies toward the seabed, a receiver that converts reflected signals from the seabed and the subsea floor layer into electrical signals, and this receiver. a plurality of discriminating means for discriminating the output of the above into signal components corresponding to the different frequencies, an amplifier for amplifying the output of the discriminating means, and detecting a signal component reflected from the seabed from the output of at least one of the discriminating means. The apparatus comprises a detecting means, a means for suppressing the amplification factor of at least one of the amplifiers using the output of the detecting means, and a recording means for superimposing and recording the outputs of the amplifying means.

Next, an embodiment of the submarine geological exploration apparatus according to the present invention will be described with reference to FIG.

FIG. 2 shows a case in which sound waves of two frequencies are used, and a transmitting section 41 consisting of a plurality of sound sources 11a, 11b and transmitting circuits 12a, 12b receives a starting pulse from a control pulse generating circuit 20 of a receiving section 42. and send at the same time. Reflected waves from the seabed and the geological interface under the seabed are received by a wave receiver 13, converted into electrical signals, separated by a high-pass filter 14 and a low-pass filter 15, and then sent to preamplifiers 16a and 15, respectively.
16b and bandpass filter 18a, 1
8b. In the preamplifier, gain control circuits 17a and 17b suppress reverberation immediately after transmission, and a high frequency preamplifier 16a and bandpass filter 18
The output of the signal a is input to a seabed detection pulse generation circuit 19 to detect the seabed and generate a seabed pulse, and the gain of the low frequency range preamplifier 16b is controlled by the gain control circuit 17b using this seabed pulse.

In other words, the low frequency preamplifier 16b suppresses the gain immediately after transmission and immediately after detecting the seabed, and the gain control circuit 17
The gain is restored with the time constant set in b. This gain suppression recovery time constant can be adjusted arbitrarily, so that when the received signal of the high frequency range preamplifier 16a becomes small, the low frequency range preamplifier 16b
gains can be restored. The outputs of the respective bandpass filters 18a and 18b are superimposed in a superimposing circuit 21, amplified to a recording level in a recording amplification circuit 22, and supplied to a recording circuit 23 of a recording section 43, where they are displayed on recording paper as a replica of the cross-section of the seabed substratum structure. do. Further, the synchronizing pulse generating circuit 24 generates a reference pulse synchronized with the recording machine sweep of the recording section.

By using the submarine geological exploration device according to the above-described embodiments, it is possible to conduct deep exploration while maintaining high resolution in shallow areas during exploration of the submarine substratum, thereby improving exploration efficiency, improving the image quality of exploration records, and improving exploration. The effect is significant in terms of cost economy.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a conventional submarine geological exploration device, and FIG. 2 is a structural diagram of a submarine geological exploration device according to the present invention. 11a, 11b...sound source (transmitter), 12a, 1
2b... Transmission circuit, 13... Receiver, 14... High pass filter, 15... Low pass filter, 16a, 1
6b...Preamplifier, 17a, 17b...Gain control circuit, 18a, 18b...Band pass filter, 19
... seabed detection pulse generation circuit, 20 ... control pulse generation circuit, 21 ... superposition circuit, 22 ... recording amplification circuit,
31, 41... Transmitting section, 32, 42... Receiving section, 3
3,43...recording department.

Claims (1)

[Claims] 1. A transmitter that emits a plurality of sound waves with different frequencies toward the seabed, a receiver that converts reflected signals from the seabed and the subsea floor layer into electrical signals, and a receiver a plurality of discriminating means for discriminating the output into signal components corresponding to the different frequencies, an amplifier for amplifying the output of the discriminating means, and a detection for detecting a reflected signal component from the seabed from at least one output of the discriminating means. A submarine geological exploration device comprising: means for suppressing the amplification factor of at least one of the amplifiers by the output of the detecting means; and recording means for superimposing and recording the outputs of the amplifying means. . 2. The submarine geological exploration apparatus according to claim 1, wherein at least one output of the discriminating means, which is an input of the detection means, is a signal corresponding to the highest frequency. 3. The submarine geological exploration device according to claim 1, wherein the number of frequencies is two.