Separation of Intrinsic and Scattering Attenuation Using Single Event Source in South Korea

Abstract

Simultaneous use of numerous events in the multiple lapse time window analysis (MLTWA) method is the most effective way to obtain Q −1 i and Q −1 S values. Such simultaneous use of numerous events normally shows a large observational scatter, which may be caused by different radiation pattern and focal depth of each earthquake, and regional alteration of the local structure. To avoid these scattering factors, the current study attempted to use single event source as the input data in MLTWA for South Korea. The direct simulation Monte Carlo (DSMC) method was used to simulate the observations, which showed realistic results when the number of recorded stations was eight or more. The obtained values of seismic albedo (B 0 ) were less than 0.5, which were in accordance with the same in the previous results. Three envelopes constructed by combination of three regional values of Q −1 Lg at 1 Hz produced regional variations, of which the ones at high frequencies of Q −1 i and at low frequencies of Q −1 S were remarkable. This result, showing the local variation indicated an advantage of the study using single source event over the previous studies in South Korea that involved extensively distributed data. Because DSMC was known to be applicable to 3D structure due to its simple algorithm, the current study also tried to correct radiation pattern of the observations by inserting focal mechanism algorithm to the code of the DSMC method. Such insertion, however, generated extremely low values of Q −1 S because the geometrically shrunk receiver could not capture most of the scattered particles. This receiver problem is most likely to be a major obstacle of the 3D study of DSMC. In addition, the significant depth effect of Q −1 was identified for the prior MLTWA studies resulting from different measurement range and focal depth.

Coda Wave Attenuation Characteristics for North Anatolian Fault Zone, Turkey

“…The change in Qc as the depth increases, in other words as the lapse time increases has become a subject which many researchers have become interested in.Such studies are numerous especially inactive tectonic areas. In the studies when the lapse timeis 20 sec., [9] calculated Qc = 29f 0.9 in their study at Etna and Granada, [12] calculated Qc = 64f 0.9 in their study at volcanic area in the southeastern area of Sicily, [13] calculated Qc = 66f 1.16 in the Koyna area, and in the studies performed with a lapse time of 20 sec., Qc = 96f 1.09 had been calculated, and in the studies performed with a lapse time 40 sec. Qc = 131f 1.04 had been calculated.…”

CodaQin Different Tectonic Areas, Influence of Processing Parameters

“…Interpretation of the coda Q results in terms of scattering and intrinsic Q is not an exact science, as evidenced by the many often conflicting proposals (e.g., Frankel and Wennerberg, 1987;Bianco et al, 2002;Carcole and Sato, 2010;Rachman et al, 2015) and is out of scope for this study. We will also not try to compare coda Q estimates from our study with studies using other methods.…”

Anomalous attenuation of high-frequency seismic waves in Taiwan: observation, model and interpretation

“…(mainly western Europe) are marked by blue diamonds (Lacombe et al, 2003;Sens-Schönfelder & Wegler, 2006;Sens-Schönfelder et al, 2009) and volcanoes by red diamonds (Mayeda et al, 1992;Del Pezzo et al, 2001;Wegler, 2003;Ugalde et al, 2010). Minimum and maximum values for absorption and scattering in Japan (Carcolé & Sato, 2010), Korea (Rachman et al, 2015) and North America (Eulenfeld & Wegler, 2017) are also shown.…”