Seismic source influence in pulse attenuation studies

Abstract

Analysis of pulse rise time data produced from repetitive piezoelectric and magnetostrictive seismic sources shows that the change in rise time as a function of distance is source dependent. Thus a linear rise time law of the form τ = τ0 + CT/Q, with C source independent, cannot be used to assess the attenuation of rock in situ. In fact, application of such a law to the data results in a significant overestimate in the value of Q. A numerical example is also presented to show that in terms of filter theory a linear rise time law is ill founded. An alternative, source independent method of assessing the attenuation is employed for both constant‐Q and non‐constant‐Q models, and it is found that either model may be made to give a reasonable fit to the data. However, it is shown that if a non‐constant‐Q mechanism is operating, then there is probably less than a 5% change in Q over the frequency range 0.80–70.OkHz.

2-D Image of Seismic Attenuation beneath the Deep Seismic Sounding Profile "Quartz," Russia

“…JANNSEN et al (1985), BADRI and MOONEY (1987), TONN (1989, 1991), and MATHENEY and NOWACK (1995 compared different techniques, finding that each of these methods work well in favourable situations while some of them have significant limitations. Thus, amplitude-decay techiques strongly depend on the correct evaluation of the geometric spreading effects; pulse broadening and time rise approaches are often source-dependent (BLAIR and SPATHS, 1984). On the contrary, spectral ratio methods and related techniques employing instantaneous wavelet attributes are less affected by focusing and source signature.…”

NEAR‐SOURCE PULSE PROPAGATION: APPLICATION TO Q‐DETERMINATION1

“…Blair andSpathis 1982, 1984;Badri and Mooney 1987;Hatherly 1986;Newman and Worthington 1982;Tonn 1989Tonn , 1991Jongmans 1990a). Two main methods are generally used to determine the seismic wave attenuation factor or its inverse, the quality factor Q.…”

Seismic Neighboring Traces Attenuation Tomography in Time Domain

“…Gladwin and Stacey [4] made use of the pulse broadening phenomena of waves in propagation to propose a rise-time principle. Kjartansson [5] and Blair et al [6,7] . further developed this principle, and estimated the quality factor (Q-value) with rise-time.…”