S-wave attenuation in northeastern Sonora, Mexico, near the faults that ruptured during the earthquake of 3 May 1887 Mw 7.5

Abstract

We used a new data set of relocated earthquakes recorded by the Seismic Network of Northeastern Sonora, Mexico (RESNES) to characterize the attenuation of S-waves in the fault zone of the 1887 Sonora earthquake (Mw 7.5). We determined spectral attenuation functions for hypocentral distances (r) between 10 and 140 km using a nonparametric approach and found that in this fault zone the spectral amplitudes decay slower with distance at low frequencies (f < 4 Hz) compared to those reported in previous studies in the region using more distant recordings. The attenuation functions obtained for 23 frequencies (0.4 ≤ f ≤ 63.1 Hz) permit us estimating the average quality factor QS = (141 ± 1.1 )f(0.74 ± 0.04) and a geometrical spreading term G(r) = 1/r0.21. The values of Q estimated for S-wave paths traveling along the fault system that rupture during the 1887 event, in the north–south direction, are considerably lower than the average Q estimated using source-station paths from multiple stations and directions. These results indicate that near the fault zone S waves attenuate considerably more than at regional scale, particularly at low frequencies. This may be the result of strong scattering near the faults due to the fractured upper crust and higher intrinsic attenuation due to stress concentration near the faults.Electronic supplementary materialThe online version of this article (doi:10.1186/2193-1801-3-747) contains supplementary material, which is available to authorized users.

Erratum to: S-wave attenuation in northeastern Sonora, Mexico, near the faults that ruptured during the earthquake of 3 May 1887 Mw 7.5

“…Black continuous line corresponds to the attenuation function found for the horizontal spectral amplitudes (cm/s 2 ) and dashed line corresponds to the attenuation function found for the vertical component of the acceleration spectral amplitudes (cm/s 2 ). This is the corrected Figure 6 in Villalobos-Escobar and Castro ( 2014 ).

Figure 2 Attenuation functions obtained for event 9 ( M L =3.5) for 10 of the 23 frequencies studied.

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“…The dots are the observed horizontal spectral amplitudes of event 9, continuous line represents the un-scaled attenuation function and the dashed line represents the attenuation function scaled by its respective source-size factor. This is the corrected Figure 7 in Villalobos-Escobar and Castro ( 2014 ).

Figure 3 Estimates of b (left frame) and Q (right frame) for N = 1.0 (see equation (4)) for the whole hypocentral distance range (10-140km).

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Figure 3 Estimates of b (left frame) and Q (right frame) for N = 1.0 (see equation (4)) for the whole hypocentral distance range (10-140km). This is the corrected Figure 8 in Villalobos-Escobar and Castro ( 2014 ).

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“…In the original version of this article (Villalobos-Escobar and Castro 2014 ), Figures 6, 7, and 8 were marked up incorrectly. Figure 6 should show examples of nonparametric attenuation functions, instead the incorrect Figure 6 shows values of the exponent b of the geometrical spreading function (equation 4) and estimates of the quality factor Q .…”