Publication Date:
2017-04-04
Description:
The deep structure of the North Ligurian margin and its contiguous Ligurian basin as well as the seismicity
recorded in these zones are neither well understood nor precisely constrained. In order to better address these questions,
there is a need for offshore instrumenting, which was realised for a duration of nearly 6 months during the GROSMarin
(Grand Réseau d’Observation Sous-Marin) experiment. An array of 21 ocean bottom seismometers was deployed over
the most active area of the margin and was complemented on land by mobile seismological stations that densified existing
permanent networks. We also realised the acquisition of deep refraction seismic shots at sea in order to get a 3D distribution
of velocities along the margin through travel time tomography. We present here a preliminary analysis of the
seismicity recorded during this experiment and a tomographic model of the margin structures obtained using data from
the offshore network only. Our results support the existence of a high velocity zone at the base of a domain interpreted
as transitional between continental and oceanic ones, on the northern part of the deep basin. A very similar pattern is observed
across the neighbouring margin of the Gulf of Lions and is most likely related to serpentinisation of the underlying
mantle during late rifting and continental break-up. North of this transition zone, we observe the basinward crustal
thinning of the continental crust beneath the margin that seemingly narrows eastward. To the south, our results hint at
transition to the oceanic domain. In contrast, our velocity distribution does not reveal a transition along strike between
transitional and oceanic domains, as previous works suggest. Some microseismic activity was recorded throughout the
duration of the experiment, on land and at sea. The number of detected events and precision of location were both
improved by our considering French and Italian permanent networks. The detection capabilities of our dense network
still need to be fully exploited
Description:
Published
Description:
305-321
Description:
3.3. Geodinamica e struttura dell'interno della Terra
Description:
JCR Journal
Description:
restricted
Keywords:
North Ligurian margin
;
Ocean bottom seismometers
;
Refraction tomography
;
Velocity structure
;
Crustal units
;
Microseismicity
;
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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