Publication Date:
2022-03-07
Description:
The Pollino range is a region of slow deformation where earthquakes generally nucleate on
low-angle normal faults. Recent studies have mapped fault structures and identified fluid related
dynamics responsible for historical and recent seismicity in the area. Here, we apply
the coda-normalization method at multiple frequencies and scales to image the 3-D P-wave
attenuation (QP) properties of its slowly deforming fault network. The wide-scale average
attenuation properties of the Pollino range are typical for a stable continental block, with a dependence
of QP on frequency of Q−1
P
= (0.0011 0.0008) f (0.36 0.32). Using only waveforms
comprised in the area of seismic swarms, the dependence of attenuation on frequency increases
[Q−1
P
= (0.0373 0.0011) f (−0.59 0.01)], as expected when targeting seismically active faults.
A shallow very-low-attenuation anomaly (max depth of 4–5 km) caps the seismicity recorded
within the western cluster 1 of the Pollino seismic sequence (2012, maximum magnitude
Mw = 5.1). High-attenuation volumes below this anomaly are likely related to fluid storage
and comprise the western and northern portions of cluster 1 and the Mercure basin. These
anomalies are constrained to the NW by a sharp low-attenuation interface, corresponding to
the transition towards the eastern unit of the Apennine Platform under the Lauria mountains.
The low-seismicity volume between cluster 1 and cluster 2 (maximum magnitude Mw = 4.3,
east of the primary) shows diffuse low-to-average attenuation features. There is no clear indication
of fluid-filled pathways between the two clusters resolvable at our resolution. In this
volume, the attenuation values are anyway lower than in recognized low-attenuation blocks,
like the Lauria Mountain and Pollino Range. As the volume develops in a region marked
at surface by small-scale cross-faulting, it suggests no actual barrier between clusters, more
likely a system of small locked fault patches that can break in the future. Our model loses
resolution at depth, but it can still resolve a 5-to-15-km-deep high-attenuation anomaly that
underlies the Castrovillari basin. This anomaly is an ideal deep source for the SE-to-NW
migration of historical seismicity. Our novel deep structural maps support the hypothesis
that the Pollino sequence has been caused by a mechanism of deep and lateral fluid-induced
migration.
Description:
Natural Environment Research Council (NERC) Centre for Doctoral Training (CDT) in Oil and Gas.
University of Aberdeen.
Description:
Published
Description:
536–547
Description:
4T. Sismicità dell'Italia
Description:
JCR Journal
Keywords:
body waves
;
seismic attenuation
;
seismic tomography
;
04.06. Seismology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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