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Seismic tomography of the area of the 2010 Beni-Ilmane earthquake sequence, north-central Algeria.

Abacha I, Koulakov I, Semmane F, Yelles-Chaouche AK - Springerplus (2014)

Bottom Line: This sequence, which lasted several months, was triggered by conjugate E-W reverse and N-S dextral faulting.These high values may indicate high fluid contents in the aftershock area.These fluids could have been released from deeper levels by fault movements during earthquakes and migrated rapidly upwards.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche en Astronomie, Astrophysique et Geophysique, BP. 63, Bouzareah, Alger, Algeria.

ABSTRACT
The region of Beni-Ilmane (District of M'sila, north-central Algeria) was the site of an earthquake sequence that started on 14 May 2010. This sequence, which lasted several months, was triggered by conjugate E-W reverse and N-S dextral faulting. To image the crustal structure of these active faults, we used a set of 1406 well located aftershocks events and applied the local tomography software (LOTOS) algorithm, which includes absolute source location, optimization of the initial 1D velocity model, and iterative tomographic inversion for 3D seismic P- and S-wave velocities (and the Vp/Vs ratio), and source parameters. The patterns of P-wave low-velocity anomalies correspond to the alignments of faults determined from geological evidence, and the P-wave high-velocity anomalies may represent rigid blocks of the upper crust that are not deformed by regional stresses. The S-wave low-velocity anomalies coincide with the aftershock area, where relatively high values of Vp/Vs ratio (1.78) are observed compared with values in the surrounding areas (1.62-1.66). These high values may indicate high fluid contents in the aftershock area. These fluids could have been released from deeper levels by fault movements during earthquakes and migrated rapidly upwards. This hypothesis is supported by vertical sections across the study area show that the major Vp/Vs anomalies are located above the seismicity clusters.

No MeSH data available.


Related in: MedlinePlus

Examples reconstructions for six models with single synthetic anomalies 3×3 km of lateral size placed in different parts of the study region to further investigate the effect of smearing. In all these cases, the amplitudes of anomalies were 5%.
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Fig4: Examples reconstructions for six models with single synthetic anomalies 3×3 km of lateral size placed in different parts of the study region to further investigate the effect of smearing. In all these cases, the amplitudes of anomalies were 5%.

Mentions: Seismo-tectonic context of the 2010 Beni-Ilmane seismic sequence (fromYelles et al.2013)with the seismic networks. The brown rectangles represent the drillings in the region and some among them attained around 4000 m of depth. The red dashed box shows the tomography area shown in Figures 3,4 and6.


Seismic tomography of the area of the 2010 Beni-Ilmane earthquake sequence, north-central Algeria.

Abacha I, Koulakov I, Semmane F, Yelles-Chaouche AK - Springerplus (2014)

Examples reconstructions for six models with single synthetic anomalies 3×3 km of lateral size placed in different parts of the study region to further investigate the effect of smearing. In all these cases, the amplitudes of anomalies were 5%.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230316&req=5

Fig4: Examples reconstructions for six models with single synthetic anomalies 3×3 km of lateral size placed in different parts of the study region to further investigate the effect of smearing. In all these cases, the amplitudes of anomalies were 5%.
Mentions: Seismo-tectonic context of the 2010 Beni-Ilmane seismic sequence (fromYelles et al.2013)with the seismic networks. The brown rectangles represent the drillings in the region and some among them attained around 4000 m of depth. The red dashed box shows the tomography area shown in Figures 3,4 and6.

Bottom Line: This sequence, which lasted several months, was triggered by conjugate E-W reverse and N-S dextral faulting.These high values may indicate high fluid contents in the aftershock area.These fluids could have been released from deeper levels by fault movements during earthquakes and migrated rapidly upwards.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche en Astronomie, Astrophysique et Geophysique, BP. 63, Bouzareah, Alger, Algeria.

ABSTRACT
The region of Beni-Ilmane (District of M'sila, north-central Algeria) was the site of an earthquake sequence that started on 14 May 2010. This sequence, which lasted several months, was triggered by conjugate E-W reverse and N-S dextral faulting. To image the crustal structure of these active faults, we used a set of 1406 well located aftershocks events and applied the local tomography software (LOTOS) algorithm, which includes absolute source location, optimization of the initial 1D velocity model, and iterative tomographic inversion for 3D seismic P- and S-wave velocities (and the Vp/Vs ratio), and source parameters. The patterns of P-wave low-velocity anomalies correspond to the alignments of faults determined from geological evidence, and the P-wave high-velocity anomalies may represent rigid blocks of the upper crust that are not deformed by regional stresses. The S-wave low-velocity anomalies coincide with the aftershock area, where relatively high values of Vp/Vs ratio (1.78) are observed compared with values in the surrounding areas (1.62-1.66). These high values may indicate high fluid contents in the aftershock area. These fluids could have been released from deeper levels by fault movements during earthquakes and migrated rapidly upwards. This hypothesis is supported by vertical sections across the study area show that the major Vp/Vs anomalies are located above the seismicity clusters.

No MeSH data available.


Related in: MedlinePlus