SU881568A1 - Seismic station - Google Patents

Description

(54) SEISMIC STATION

one

The invention relates to seismic reconnaissance and can be used to record seismic information,

A method and apparatus are known for accumulating, summing and correlating seismic data 1.

The device consists of a reference driver, a controlled vibrator, seismic channels of the receiving signal, a magnetic accumulator, a correlator and a recorder.

When the device is operated, the vibration effects are carried out according to a predetermined program and the results are recorded in the storage device in analog form. After several such cycles, the results are correlated and summed up, which are recorded.

The disadvantage of such a system is that the correlation is carried out after the observation.

Also known is a seismic survey method with a vibratory excitation source implemented by a device consisting of the same blocks as described, but the information is not represented in analogue, but in digital form, converted to one-bit form. This leads to the loss of part of the information, but allows the correlation

 in the process of observing in real

 time scale 2.

A disadvantage of this device is the time constraint of the reference signal.

10 The closest technical solution to the present invention is a device for conducting vibration seismic surveys and processing the obtained data. The source of seismic disturbances is a conventional vibrator with adjustable phases or a vibrator that creates rectangular pulses. In these cases, the vibrators are controlled by a variable frequency sinusoidal signal generated by a reference signal generator, the designs of which may be different. The recording system consists of an amplifier with

25 large constant gain, single-digit converters analog - code, correlator, operating with single-digit numbers, adder and magnetic recorder

30 resulting data.

This device uses the usual correlation scheme based on changing the reference and studied signals, obtaining the products of their values in discrete time intervals and forming the sum of a number of products for the corresponding time period 3.

However, in the process of one-bit encoding, inevitably, an error occurs that leads to a correlation error. A disadvantage of the known device is also the limited duration of the reference signal, and an increase in the duration of the reference signal, all other things being equal, increases the signal-to-noise ratio; the limitation of the duration of the reference signal is due to the design itself - the capacity of the recorder, and fundamentally unavoidable. In addition, a controlled vibrator is required for the operation. Accurate following of the vibrator active mass to the commands of the reference signal requires a rather cumbersome vibrator control system and additional energy costs, and the possibility of using manually controlled sources of vibration for seismic prospecting is excluded.

The aim of the invention is to increase the signal-to-noise ratio, increase the depth of research and simplify the design of a seismic station.

The goal is achieved by the fact that in a seismic station containing a reference signal channel, there is a series-connected reference signal sensor, an amplifier and a one-bit analog-to-code converter, a receiving signal channel that includes series-connected seismic receivers, an amplifier and a one-bit analog-code converter, and a correlator, a drive and a recorder connected in series, the output channel of the receiving signal is connected to the input of the correlator, the device is turned on at the output of each channel A device for forming the frequency composition of vibrations is turned on in the formation of signal crossings by zero through the output of the channel of the reference signal and the correlator, while the output of the accumulator is single with the input of the correlator.

. The drawing shows the structure of a seismic station.

The seismic station contains the channels of the reference 1 and receiving 2 signals, a device for forming the frequency composition of the vibration of the reference signal 3, the correlator 4, the drive 5 and the recorder 6. The reference channel 1 contains the sensor of the reference signal 7, the amplifier 8, the single-bit analog converter - code 9 and a device for forming a signal transition through zero 10. Receiving channel 2 contains seismic receivers 11, an amplifier 12, a one-bit transducer, an ana log - code 13, and a device for forming signal zero transitions. 14. Shaper frequency composition of the vibration of the reference signal 3 contains a duty cycle analyzer 15, the drive

The Q of the actual spectrum of the reference signal 16, the block of comparison 17 of the actual spectrum with the reference 18 and the resolution block 19.

The seismic station operates as follows.

5 Signals from seismic receivers 11 are installed by amplifier 12, converted into analogue by code converter by analogue code 13, centered by highlighting

0 zero crossings in block 14 are sent to the correlator 4. Signals from the reference signal sensor 7 are amplified by an amplifier 8, the analog is converted into a one-bit record by the converter — code 9, centered by selecting zero crossings by the block 10. Then determine the duty cycle between two pulses in the duty cycle analyzer 15, after

which forms a pulse in comparison block 17, where it is compared with the reference one coming from block 18. If the pulses with such a duty cycle are previously accepted below the norm, block 19 is allowed to pass this pulse to the correlator, otherwise a ban is generated. A special feature of the correlator is the use of a storage device for the formation of a coordinate mapping, for which

0 there is a feedback link between the output of the accumulator and the input of the correlator.

The implementation of the proposed device provides the benefits of methodical and feasibility

5 characters.

The methodological advantages are due to the fact that the characteristic of the correlation function, from the point of view of seismic signal extraction, improves even with the same conditions as the duration of the reference signal. The absence of limitations in the duration of the reference signal allows increasing the accumulations of the useful signal and, therefore, increasing the ratio of useful signal-interference (i.e., increasing the detail and depth of research).

Techno-economic advantages result from the fact that, especially due to the use of weak effects and the need to accumulate a useful signal, the time of action increases and exceeds the time of observation of the result of this effect.

for 2 times. In relation to this, the registration of the reference signal in the proposed device will require fewer elements. Register for the received signal in the proposed device no. All this allows to significantly reduce the cost of the device while increasing reliability.

One means of reducing the number of elements is the use of zero-crossing drivers. With one bit coding, one sinusoid is encoded by a number of consecutive positive and negative units that are involved in processing. So, at frequencies of the order of 30-40 Hz and time ticks equal to 2 ms, such units per period will be 12-15, and zero crossings per period 2. Therefore, the use of zero crossing shapers reduces information noise by 6-7 times each channel and 36–49 times after correlation. This allows you to save five bits of memory.

Certain advantages arise from the possibility of eliminating the control with a vibrator. Vibrators for seismic exploration are multi-ton structures that are difficult to maintain and transport.

The conditional economic effect from the use of this three-channel seismic station at the required facilities is 20 thousand rubles a year.

Claims (3)

1. US patent 3307145, CL. 340-155, published. 1967. 0 2. US patent No. 4037190, cl. 3-40-155.5, published. 1977. 3. US patent No. 4064481, cl. 340-155, published. 1977 (proto | type).