VARIATION IN SEISMIC NOISE AT SEISMIC STATIONS WITH IMPLICATIONS FOR EVENT DETECTION

Jamshaid Ali, M. Daud Daud, M. Qaisar, Zahid Ali

Abstract


A network of 23 analog seismic stations was established in Pakistan to monitor seismic activity. The instrumentation of seismic stations includes short period seismometers with natural period at 1 Hz. The seismic noise conditions of five seismic stations are studied to determine the detection capability in the frequency range from 1.0 Hz to 10.0 Hz regarding monitoring of local and regional seismicity. The Power spectral density of noise level of the records was computed by taking day and night samples during winter and summer seasons. The seismic noise levels at these stations range from –120 db to –157 db between 1.0 to 10 Hz, which is well within the limits defined by the Peterson’s new low and high noise model. The observed noise variations recorded during day and night range from 5 db to 17 db, depending on the site of the station. The detect-ability estimates of the selected five seismic stations installed at Fort Munroe, Cherat, Thammi Wali, Dhulian and Sargodha assume a conservative signal-to-noise ratio of 3. These stations showed detection capability 3.1, 3.3, 3.4, 3.5 and 3.8 magnitudes at 1000 km distance respectively.

Full Text:

Untitled

References


Abdel Gawad, M., (1971). Wrench movements in the Baluchistan arc and relation to Himalayan-Indian ocean tectonics. Bull Geol. Soc. Am., V. 82, pp. 1235-1250.

Aki, K., & Richard, P. G., (1980). Quantitative seismology. Freeman, San Francisco, V. I, p. 498.

Bormann, P., (1998). Conversion and comparability of data presentations on seismic back ground noise. J. Seism., V. 2, pp. 37-45.

Dewey, J. & Bird, J. (1970). Mountain belts and the new global tectonics. J. Geophys. Res., V. 75, pp. 2625-2647.

Gansser, A., (1964). Geology of the Himalayas. Wiley, New York, p. 289.

Islam, S. R., (1959). The Indus submarine canyon. Pak. Geog. Review, V. 14, pp. 32-34.

Jacob, K. H. & Quittmeyer, R. L., (1979). The Makran region of Pakistan and Iran: Trench arc system with active plate subduction. In: Geodynamics of Pakistan (Farah, A. & Dejong K. A., eds). Geol. Surv., Quetta, pp. 305-317.

Kazmi, A. H., (1966). Geology of Indus plain. Geology Dept., Cambridge Univ., U. K., p. 98.

Kazmi, A. H., and Jan, M. Q., (1977). Geology and tectonics of Pakistan, Graphic publishers Karachi, Pakistan.

Molnar, P. & Tapponier, P., (1975). Cenozoic tectonics of Asia: effects of continental collision. Science, V. 189, pp. 419-426.

McKenzi, D. & Sclater J. G., (1971). The evaluation of Indian Ocean since the late Cretaceous. Royal Astron. Soc. Geophys. J., V. 24.

Nowroozi, A., (1971). Seismo-tectonics of the Persian plate, Eastern Turkey, Caucasus and Hindu Kush region. Bull. Seism. Soc. Am., V. 61, pp. 823-850.

Peterson, J., (1993). Observations and modeling of seismic back ground noise. U. S. Geol. Survey Open–File Report 93-322, p. 95.

Richter, C. F., (1958). Elementary Seismology, W.H. Freeman & Co., San Francisco.

White, R. S., (1979). Deformation of the Makran Continental margin. Geol. Surv. Pak., Quetta.

Withers, M. M., R. C. Aster, C.J. Young and E.P. Chael, (1996): High frequency analysis of seismic background noise as function of wind speed and shallow depth, Bull. Seism. Soc. Am., V. 86, pp. 1507-1515.

Young, C. J., E. P. CHAEL, M. M. Wither and R. C. Aster, (1996). A comparison of the high (› 1 Hz) surface and subsurface noise environment at three sites in the United States, Bull. Seism. Soc. Am., V. 86, pp. 1516-1528.


Refbacks

  • There are currently no refbacks.

Couldn't lock the file.