Publication Date:
2017-04-04
Description:
The three-dimensional pattern of elastic moduli (bulk modulus, Young modulus,
shear modulus) of the upper crust (0-10 km depth) has been determined in the Friuli
area (north-eastern Italy) from the 3D Vp, Vp/Vs and density structures. Firstly, 3D Pwave
velocity and P to S velocity ratio were modeled by joint inversion for
hypocentres and velocity structure. Then, we apply the tomographic inversion method
of Sequential Integrated Inversion (SII) to recover the three dimensional density
structure. The pattern of the elastic moduli is characterized by marked lateral and
depth variations that reflect the geologic-structural heterogeneity of the area,
produced by the superposition of several tectonic phases with different orientations
of the principal axes of stress. The bulk (K), Young (E) and shear (G) moduli image
a high rigidity body with an irregular shape, at 4-8 km depth. The body is
characterized by G ≥ 3.2·1010 N·m-2, K ≥ 6.8·1010 N·m-2 and E ≥ 8.4·1010 N·m-2 and is
associated to platform limestones and dolomitic rocks. The seismicity is mainly
located along the sharp variations of the moduli pattern, in or adjacent to high rigidity
zones. The most severe earthquakes (ML between 4.5 and 6.4), occurred in the study
area from 1976 to the present day, are located in a transition zone from high to low
rigidity patterns. Our interpretation is that the elastic moduli variations, closely related
to variability in rock mechanical properties, influence the occurrence of earthquakes
by processes of stress concentrations. The values of the elastic moduli recently
obtained from laboratory measurements on the main lithologic units fall in the middlehigh
range of the values obtained with the present investigation.
Keywords: Seismic tomography, gravity anomalies, seismicity, elastic moduli, Friuli, NE Italy
Description:
Published
Description:
191-212
Description:
3.3. Geodinamica e struttura dell'interno della Terra
Description:
JCR Journal
Description:
restricted
Keywords:
Seismic tomography
;
gravity anomalies
;
seismicity
;
elastic moduli
;
Friuli
;
NE Italy
;
04. Solid Earth::04.01. Earth Interior::04.01.04. Mineral physics and properties of rocks
;
04. Solid Earth::04.02. Exploration geophysics::04.02.02. Gravity methods
;
04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
;
04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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