Seismic coda attenuation after the M_w = 6.2 Armenia (Colombia) earthquake of 25 January 1999

Abstract

[1] Seismic wave attenuation in the central region of the Colombian Andes is studied using coda waves. Most of the events used occurred in the region on the occasion of the Armenia 25 January 1999 earthquake. The estimation of the decay rate of coda amplitudes (called coda Q À1 or Q c À1 ) is performed by means of the single isotropic scattering method of Sato [1977]. The attenuation parameters Q i À1 (intrinsic absorption), Q s À1 (scattering loss), and Q t À1 (total attenuation) are also estimated using the multiple lapse time window method of Hoshiba et al. [1991]. The frequencies of interest lie between 1 and 15 Hz. Results show that scattering attenuation is predominant for the frequency bands 1.5 ± 0.5 and 13.5 ± 1.5 Hz, whereas the intrinsic absorption and scattering contribute in equal shares to total attenuation for the 3 ± 1, 5 ± 1, 7.5 ± 1.5, and 10.5 ± 1.5 Hz frequencies. A comparison among the estimated attenuation parameters indicates that Q c À1 is close to total attenuation for all the studied frequency bands. On the other hand, no evidence in support of temporal changes of Q c À1 before and after the main shock has been found. Finally, the regionalization of Q c À1 values seems to correlate well with the geotectonic characteristics of the region.INDEX TERMS: 7203 Seismology: Body wave propagation; 7218 Seismology: Lithosphere and upper mantle; 9360 Information Related to Geographic Region: South America;

Variation of Seismic Coda Wave Attenuation in the Garhwal Region, Northwestern Himalaya

“…The frequency dependency parameter estimated in this region is higher as compared to other regions indicating more heterogeneous upper lithosphere; however, it is similar to that for the northwestern Himalaya, Garwhal Himalaya, Turkey, Italy, Spain. Variation of frequency parameter is also not significant at smaller LT and shallow events in some other parts of the world (IBANEZ et al, 1990; Washington (Havskov et al, 1989) Western Anotolia (Akinci et al, 1994) Kutch (Gupta et al, 2006) Koyna (Gupta et al, 1998) Garhwal Himalaya (Gupta et al, 1995) Western Himalaya (Kumar et al, 2005) Dead Sea (Van Eck, 1988) Western Himalaya (Mukhopadhyay et al, 2006) Colombia (Ugalde et al, 2002) Southern India (Tripathi & Ugalde, 2004) Chamoli (Mandal et al, 2001) Bhuj (Mandal et al, 2004) Koyna (Mandal & Rastogi, 1998) Maxico (Rodriguez et al, 1983 (Gupta et al, 1995) Western Himalaya (Kumar et al, 2005) Western Himalaya (Mukhopadhyay et al, 2006) Chamoli (Mandal et al , 2001) Western et al, 1994). The coda attenuation parameter estimated in the present study is comparable to the estimates obtained by other workers for the Indian lithosphere (GUPTA et al, 1995(GUPTA et al, , 1998(GUPTA et al, , 2006MANDAL and RASTOGI, 1998;MANDAL et al, 2001MANDAL et al, , 2004TRIPATHI and UGALDE, 2004;KUMAR et al, 2005;MUKHOPADHYAY et al, 2006).…”

“…The single scattering model of AKI and CHOUET, (1975) was extended to non-coincident source and receiver by SATO (1977), thus enabling one to analyze the coda waves just after the S-wave arrival. The Q c , quality factor of coda wave, has been estimated extensively in different parts of the world (AKI and CHOUET, 1975;SATO, 1977;ROECKER et al, 1982;PULLI, 1984;WU, 1985;DEL PEZZO et al, 1987AKI, 1988, 1989;HAVSKOV et al, 1989;IBANEZ et al, 1990;PUJADES et al, 1991;CANAS et al, 1991;AKINCI et al, 1994;LATCHMAN et al, 1996;ZELT et al, 1999;UGALDE et al, 2002;TRIPATHI and UGALDE, 2004;GIAMPICCOLO et al, 2004;YUN et al, 2007) and the conclusion is that, in general, it is higher in stable regions and lower in tectonically active regions (SATO and FEHLER, 1998). The estimated Q c values well fit the frequency dependent power law relation (Q c af n ) at higher frequencies (f [ 1 or so).…”

S-waves attenuation and separation of scattering and intrinsic absorption of seismic energy in southeastern Sicily (Italy)

“…Finally, since the MLTWA technique has been widely applied to several areas in the world (e.g. Mayeda et al 1992; Hoshiba 1993; Akinci et al 1995; Pujades et al 1997; Akinci & Eydoğan 2000; Bianco et al 2002; Ugalde et al 2002; Bianco et al 2005), differences and analogies observed among southeastern Sicily and other tectonic settings will be discussed.…”

Deep Earth Structure: Seismic Scattering in the Deep Earth

“…Single-scattering studies include Sato (1978), Aki (1980), Pulli (1984), Dainty et al (1987), Kosuga (1992), and Baskoutas (1996). Multiple lapse-time studies are summarized in Figure 5 and include Fehler et al (1992), Mayeda et al (1992), Hoshiba (1993), Jin et al (1994), Akinci et al (1995), Canas et al (1998), Ugalde et al (1998Ugalde et al ( , 2002, Hoshiba et al (2001), Bianco et al (2002Bianco et al ( , 2005, Vargas et al (2004), Goutbeek et al (2004), Mukhopadhyay and Tyagi (2008), Badi et al (2009), Chung et al (2010, Carcolé and Sato (2010), Lee et al (2010), and Del Pezzo et al (2011). Values of the coefficient go for S-to-S scattering range from about 0.002 to 0.05 km À1 (mean free paths of 20-500 km) for frequencies between 1 and 30 Hz.…”