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Seismic shots

Detonating cords are also employed for seismic shots in the desert and at sea. They are also used for clearing blasts in oil and gas wells, which restore the flow from blocked boreholes special cords with a wire reinforced sheat are used for this purpose. [Pg.131]

Fig. 8. Onshore seismic field operation, using the shot hole energy method. Energy from a controlled explosion is directed toward underlying rock structures and is reflected to indicate shape of formation below—in this case an anticline. Geophones placed on the ground surface by the surveying crew measure and record the reflected acoustic energy. With the survey truck safely away from the shot hole, the explosives are detonated by an assigned radio frequency from tile truck... Fig. 8. Onshore seismic field operation, using the shot hole energy method. Energy from a controlled explosion is directed toward underlying rock structures and is reflected to indicate shape of formation below—in this case an anticline. Geophones placed on the ground surface by the surveying crew measure and record the reflected acoustic energy. With the survey truck safely away from the shot hole, the explosives are detonated by an assigned radio frequency from tile truck...
Cook (Ref) reported that only the S-wave and the induced ground wave were apparent in seismic disturbances from surface explns at Tooele, Utah and for unconfined or dirt-covered shots the induced ground wave had an index 5-30 times greater than the S-wave. Synchronous ground-wave induction apparently requires simply matching of the frequency of the air blast with the natural frequency of the ground in the region of the blast. [Pg.426]

Seismic Waves from a Shot-Generated Cavity , Suppl Note, Geological Survey, Menlo Park, Ca (1967) 50) L. Rudlin et al, The Early... [Pg.767]

Teller contrived nevertheless to follow the progress of the test. He stationed himself at a seismograph in a basement room of the Berkeley geology building. Herbert York, acting director at Livermore, timed a shortwave radio to the frequency of the Mike shot telemetry. When the shot was fired he called Teller in Berkeley. The two physicists had calculated the time a seismic wave from a successful shot would require to travel under the Pacific basin to northern California— about fifteen minutes. Teller remembers ... [Pg.777]

The seismic reflection method is the most extensively used of all geophysical techniques, its principal employment being in the oil industry. In this technique, the depth of investigation is large compared with the distance from the shot to detector array. This is to exciude refraction waves. Indeed, the method is able to record information from a large number of horizons down to depths of several thousands of metres. [Pg.349]

Seismic ground motions may be modeled as a zero-mean filtered Gaussian shot-noise random process with a Kanai-Tajimi spectrum... [Pg.5]

If the OBS experiment is combined with multichannel or wide-angle seismics, the recorded airgun shots of the seismic profiles can be used to determine the position of the instmment on the seafloor. The calculation will be done after recovery no additional ranging with the onboard unit is necessary. The procedure is similar to the direct ranging via the acoustic release unit at least three shots evenly distributed around the OBS are necessary. Knowing the exact time and position of the shots, the sound velocity of water, and the water depth, the distances between... [Pg.1745]

In case if a volcano is located close to the seashore, it is possible to use underwater air guns as sources of seismic signal (Fig. 2a). The advantage is that air-gun shots are rather cheap... [Pg.3118]

Fig. 2 Schemes for active-source experiments using air-gun shots (a) and for ambient noise tomography (b). Blue triangles depict seismic stations red dots are sources... Fig. 2 Schemes for active-source experiments using air-gun shots (a) and for ambient noise tomography (b). Blue triangles depict seismic stations red dots are sources...
Good solutions for areas which are close to the seashore are the underwater air-gun shots which can be used to generate high-quality and sufficiently powerful seismic signal and can surround the target area (Fig. 2a). Nowadays, this scheme is widely used in experiments in many volcanic areas. Among many different studies, three examples are selected here ... [Pg.3125]

Antarctic which was studied by Zandomeneghi et al. (2009). This island has a circular shape and is suitable for performing air-gun shots inside and outside the circle. Using onshore and offshore seismometers made this observation system suitable for high-resolution tomography studies. The inversion of travel time data revealed the seismic structures down to 2 km which appeared to be linked with the main geological structures. The circular rim of the caldera is associated with high-velocity lineaments. Inside the caldera, a low-velocity anomaly is observed. [Pg.3125]

FIGURE 4 Sensitivity curve (thick solid line) for a 3-km baseline interferometer with 30-kg test masses. The sources of noise are outlined standard quantum limit (thin solid line) seismic noise (long dashed line) gravity gradient noise (dotted line) thermal noise (short dashed line) shot noise (dash-dot line). [Pg.116]

Despite the fact that the significant term for shot noise is the effective optical length NL, it is still important to have a large physical arm length L. In fact, the other sources of noise at low frequency are thermal noise and seismic noise, which are displacement noises causing the motion of the optical elements according to... [Pg.117]

The sensitivity of forthcoming laser interferometers is limited by seismic noise at low frequencies (from a few hertz to tens of hertz according to the isolation strategy), by thermal noise up to some hundreds of hertz, and by shot noise above. Other sources of noise, however, can contribute to the total noise budget ... [Pg.118]


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See also in sourсe #XX -- [ Pg.77 , Pg.277 ]




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Seismic

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