53 research outputs found
MADAM: A temporary seismological survey experiment in Aetolia-Akarnanian region (Western Greece)
The Aetolia-Akarnanian region, in Western Greece, is considered to be part of a micro-plate in formation, named the Ionian Island-Akarnanian Block (IAB), in the larger-scale Central Mediterranean tectonic context. The IAB accommodates the deformations between the surrounding tectonic structures that are the Corinth Gulf, the Hellenic subduction, the Kefalonia Transform Fault and the Apulian collision. This work presents the first results of a dense temporary seismic survey in the Aetolia-Akarnanian region (from the Amvrakikos Gulf to the Patras Gulf). Our local dense network has been designed in order to avoid gaps and to allow the recording of a major part of the Akarnania seismicity. With a semi-automatic events detection and picking program, we detected more than 15000 events from October 2015 to December 2018. With this important data set we constrained a 1D local velocity model. The comparison with the previous published models shows a possible significant velocity variation inside the region and especially at the Trichonis lake graben. Thanks to our data set and our velocity model, we precisely located 12723 seismic events with magnitude 0 < ML < 4.6, and a magnitude of completeness Mc = 1.0, that represents actually the most important catalogue for the Aetolia-Akarnania. Seismicity highlights specific seismic structures as clusters and a seismic plane below the West of Corinth Gulf that are briefly discussed
Insights for the melt migration, the volcanic activity and the ultrafast lithosphere delamination related to the Yellowstone plume (Western USA)
The YellowstoneâEast Snake River Plain hotspot track has been intensely studied since several decades and is widely considered to result from the interaction of a mantle plume with the North American plate. An integrated conclusive geodynamic interpretation of this extensive data set is however presently still lacking, and our knowledge of the dynamical processes beneath Yellowstone is patchy. It has been argued that the Yellowstone plume has delaminated the lower part of the thick Wyoming cratonic lithosphere. We derive an original dynamic model to quantify delamination processes related to mantle plumeâlithosphere interactions. We show that fast (âŒ300 ka) lithospheric delamination is consistent with the observed timing of formation of successive volcanic centres along the Yellowstone hotspot track and requires (i) a tensile stress regime within the whole lithosphere exceeding its failure threshold, (ii) a purely plastic rheology in the lithosphere when stresses reach this yield limit, (iii) a dense lower part of the 200 km thick Wyoming lithosphere and (iv) a decoupling melt horizon inside the median part of the lithosphere. We demonstrate that all these conditions are verified and that âŒ150 km large and âŒ100 km thick lithospheric blocks delaminate within 300 ka when the Yellowstone plume ponded below the 200 km thick Wyoming cratonic lithosphere. Furthermore, we take advantage of the available extensive regional geophysical and geological observation data sets to design a numerical 3-D upper-mantle convective model. We propose a map of the ascending convective sheets contouring the Yellowstone plume. The model further evidences the development of a counter-flow within the lower part of the lithosphere centred just above the Yellowstone mantle plume axis. This counter-flow controls the local lithospheric stress field, and as a result the trajectories of feeder dykes linking the partial melting source within the core of the mantle plume with the crust by crosscutting the lithospheric mantle. This counter-flow further explains the 50 km NE shift observed between the mantle plume axis and the present-day Yellowstone Caldera as well as the peculiar shaped crustal magma chambers
The cooperative IGS RT-GIMs: a reliable estimation of the global ionospheric electron content distribution in real time
The Real-Time Working Group (RTWG) of the International GNSS Service (IGS) is
dedicated to providing high-quality data and high-accuracy products for Global
Navigation Satellite System (GNSS) positioning, navigation, timing and Earth
observations. As one part of real-time products, the IGS combined Real-Time
Global Ionosphere Map (RT-GIM) has been generated by the real-time weighting
of the RT-GIMs from IGS real-time ionosphere centers including the Chinese
Academy of Sciences (CAS), Centre National d'Etudes Spatiales (CNES),
Universitat PolitĂšcnica de Catalunya (UPC) and Wuhan University
(WHU). The performance of global vertical total electron content (VTEC)
representation in all of the RT-GIMs has been assessed by VTEC from
Jason-3 altimeter for 3 months over oceans and dSTEC-GPS technique with
2Âżd observations over continental regions. According to the
Jason-3 VTEC and dSTEC-GPS assessment, the real-time weighting technique is
sensitive to the accuracy of RT-GIMs. Compared with the performance of
post-processed rapid global ionosphere maps (GIMs) and IGS combined final GIM
(igsg) during the testing period, the accuracy of UPC RT-GIM (after the
improvement of the interpolation technique) and IGS combined RT-GIM (IRTG) is
equivalent to the rapid GIMs and reaches around 2.7 and 3.0 TECU (TEC unit,
1016ÂżelÂżm-2) over
oceans and continental regions, respectively. The accuracy of CAS RT-GIM and
CNES RT-GIM is slightly worse than the rapid GIMs, while WHU RT-GIM requires a
further upgrade to obtain similar performance. In addition, a strong
response to the recent geomagnetic storms has been found in the global
electron content (GEC) of IGS RT-GIMs (especially UPC RT-GIM and IGS combined
RT-GIM). The IGS RT-GIMs turn out to be reliable sources of real-time global
VTEC information and have great potential for real-time applications including
range error correction for transionospheric radio signals, the monitoring of
space weather, and detection of natural hazards on a global scale. All the IGS
combined RT-GIMs generated and analyzed during the testing period are
available at https://doi.org/10.5281/zenodo.5042622 (Liu et al., 2021b).his research has been supported by the
China Scholarship Council (CSC). The contribution from UPC-
IonSAT authors was partially supported by the European Union-
funded project PITHIA-NRF (grant no. 101007599) and by
the ESSP/ICAO-funded project TEC4SpaW. The work of An-
drzej Krankowski is supported by the National Centre for Research
and Development, Poland, through grant ARTEMIS (grant nos.
DWM/PL-CHN/97/2019 and WPC1/ARTEMIS/2019)Peer ReviewedPostprint (published version
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