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An M (sub L) scale in northeastern Iran

Jafar Shoja-Taheri, Saeid Naserieh and Amir Hosein Ghafoorian-Nasab
An M (sub L) scale in northeastern Iran
Bulletin of the Seismological Society of America (August 2008) 98 (4): 1975-1982

Abstract

Local-magnitude scales are derived for northeastern Iran (Khorasan province) from waveform data recorded at six stations from 205 local earthquakes, ranging in distance from 10 to 600 km. By averaging the horizontal components in a single measure, we used 1506 zero-to-peak amplitudes from synthetic Wood-Anderson seismograms to determine, in a least-squares sense, the appropriate -logA (sub 0) attenuation functions, the event local magnitude, and the station corrections. Both a parametric and a nonparametric description of -logA (sub 0) is considered while performing the inversions. In both cases, the constraint of 1-mm motion recorded at 100 km for M 3.0 earthquakes was used. To evaluate the distance correction curves in determining the local magnitude, M (sub L) , in northeastern Iran we applied both linear and trilinear inversions to our datasets. The result of the linear inversion for distance correction is given by: -logA (sub 0) = (1.370 + or - 0.050)log(R/100)+(0.0020 + or - 0.0001) (R-100)+3. For trilinear inversion we have applied the Monte Carlo technique. The resulting coefficients evaluated for the area are R (sub 1) = 106+ or -5 km; R (sub 2) = 347+ or -49 km; n (sub 1) = 1.380+ or -0.045; n (sub 2) = 0.597+ or -0.132; n (sub 3) = 0.415+ or -0.236; k = 0.0033+ or -0.0003, where n (sub 1) , n (sub 2) , and n (sub 3) are the coefficients of geometrical spreading for distances from the source to R (sub 1) , R (sub 1) to R (sub 2) , and beyond R (sub 2) . k is the coefficient of inelastic attenuation. The remarkable agreement between the parametric and nonparametric results confirms that both linear and trilinear attenuation functions that we made for deriving the parametric distance correction are equally reasonable. Moreover, inversion of bootstrap replications of our dataset furnished stable solutions. Station magnitude corrections range between -0.17 and 0.27, suggesting a variable and noticeable effect of station-site properties on recorded amplitudes.


ISSN: 0037-1106
EISSN: 1943-3573
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 98
Serial Issue: 4
Title: An M (sub L) scale in northeastern Iran
Affiliation: Ferdowsi University of Mashad, Earthquake Research Center, Mashad, Iran
Pages: 1975-1982
Published: 200808
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 23
Accession Number: 2008-116857
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch map
N35°00'00" - N38°00'00", E58°00'00" - E60°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200844
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