Attenuation of Coda Waves in the Saurashtra Region, Gujarat (India)

Abstract

The attenuation characteristics based on coda waves of two areas-Jamnagar and Junagarh of Saurashtra, Gujarat (India)-have been investigated in the present study. The frequency dependent relationships have been developed for both the areas using single back scattering model. The broadband waveforms of the vertical components of 33 earthquakes (Mw 1.5-3.5) recorded at six stations of the Jamnagar area, and broadband waveforms of 68 earthquakes (Mw 1.6-5) recorded at five stations of the Junagarh area have been used for the analysis. The estimated relations for the Junagarh area are: Q c = (158 ± 5)f (0.99±0.04) (lapse time : 20 s), Q c = (170 ± 4.4)f (0.97±0.02) (lapse time : 30 s) and Q c = (229 ± 6.6)f (0.94±0.03) (lapse time : 40 s) and for the Jamnagar area are: Q c = (178 ± 3)f (0.95±0.05) (lapse time : 20 s), Q c = (224 ± 6)f (0.98±0.06) (lapse time : 30 s) and Q c = (282 ± 7)f (0.91±0.03) (lapse time : 40 s). These are the first estimates for the areas under consideration.The Junagarh area appears to be more attenuative as compared to the Jamnagar area. The increase in Q c values with lapse time found here for both the areas show the depth dependence of Q c as longer lapse time windows will sample larger area. The rate of decay of attenuation (Q -1 ) with frequency for the relations obtained here is found to be comparable with those of other regions of the world though the absolute values differ. A comparison of the coda-Q estimated for the Saurashtra region with those of the nearby Kachchh region shows that the Saurashtra region is less heterogeneous. The obtained relations are expected to be useful for the estimation of source parameters of the earthquakes in the Saurashtra region of Gujarat where no such relations were available earlier. These relations are also important for the simulation of earthquake strong ground motions in the region.

Estimation of Coda Wave Attenuation in the East Anatolia Fault Zone, Turkey

“…Vol. 169, (2012) Estimation of Coda Wave Attenuation in the East Anatolia Fault Zone 1199 (AKI and CHOUET, 1975;ROECKER et al, 1982;HAVSKOV et al, 1989;IBANEZ et al, 1990;WOODGOLD, 1994;MITCHELL, 1995;GUPTA et al, 1998GUPTA et al, , 2006GIAMPICCOLA et al, 2002;KUMAR et al, 2005;SAHIN, 2008;MITCHELL et al, 2008;SHARMA et al, 2011). MORSY et al (2011 analyzed earthquakes data at different focal depths in the Gulf of Suez, Egypt.…”

“…Attenuation variations in the earth are usually greater than the velocity variations. Attenuation studies in time or frequency domain are carried out by using either natural or artificial sources, or by various methods considering body or surface waves (MITCHELL, 1975;CORREIG and MITCHELL, 1980;ROECKER et al, 1982;PULLI, 1984;IBANEZ et al, 1990;MOHANTY et al, 2009;MUKHOPADHYAY and SHARMA, 2010;FORD et al, 2010;SHARMA et al, 2011). Low value of Q (Q \ 200) is associated with the tectonically and seismically active regions, while high value of Q (Q [ 600) is characterized of seismically inactive and stable regions.…”

Coda Q in Eastern Indian shield

“…On the other hand, the attenuation value is comparatively less than that of Indian Shield (Singh et al 1999), Jabalpur Region (Singh et al 2004), and Central India (Mandal et al 2013) at low frequencies and gradually increases and exceeds at higher frequency. Although the attenuation value is greater than that of Sourashtra (Sharma et al 2012), Kachchh (Sharma et al 2008), and NW Himalaya (Kumar et al 2005) at lower frequency, decreases marginally at higher frequency. In addition, the attenuation value though relatively greater than Himalayan arc (Singh et al 2004) at lower frequency, both converges at higher frequency.…”

“…5), lesser attenuation relative to Eastern Canada (Chun et al 1987;Shin and Herrmann 1987), Canadian Shield (Hasegawa 1985), Eastern United States (Gupta and McLaughin 1987), Central Appalachia (Shi et al 1996), Gupta and Kumar (2002) 2. Sourashtra 170f 0.97 Sharma et al (2012) 3. Kachchh 148f…”

Nevşehir ve çevresindeki volkanik yapıların sismik soğurulma yöntemi ile belirlenmesi

“…Koda dalgalarının oluşum mekanizmaları üzerinde ilk çalışma Aki [1] ve Aki ve Chouet [2] tarafından yapılmış ve Aki [3] tarafından kodanın oluşumu üzerine modeller geliştirilmiştir. Bu modellerden tek saçılma modeli günümüze değin birçok araştırmacı tarafından yaygın bir şekilde kullanılmaktadır [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Koda dalgalarından elde edilen kalite faktörü Q, tektonik olarak aktif ve durağan bölgelerin ayırımını en iyi gösteren değişkendir.…”