Developments on the EPOS-IP strain rate product

Transcription

1 Developments on the EPOS-IP strain rate product Athanassios Ganas, NOA, Greece, Vasilis Kapetanidis, NOA-NKUA, Greece Faramarz Nilfouroushan, LM, Gävle, Sweden, University of Gävle, Sweden Holger Steffen, LM, Gävle, Sweden, University of Gävle, Sweden Martin Lidberg, LM, Gävle, Sweden Aline Deprez, CNRS-UGA, Grenoble, France Anne Socquet, CNRS-UGA, Grenoble, France Andrea Walpersdorf, CNRS-UGA, Grenoble, France Antonio Avallone, INGV, Rome, Italy Nicola D Agostino, INGV, Rome, Italy Juliette Legrand, ROB, Brussels, Belgium Carine Bruyninx, ROB, Brussels, Belgium Eduard Nastase, INCDFP RA, Bucharest, Romania, Constatin Ionescu, INCDFP RA, Bucharest, Romania, Ambrus Kenyeres, BFKH, Budapest, Hungary, Tomasz Liwosz, WUT, Warsaw, Poland, Wolfgang Soehne, BKG, Frankfurt-am-Main, Germany Machiel Bos, UBI/C4G, Covilhã, Portugal Rui Fernandes, UBI/C4G, Covilhã, Portugal 1

2 OUTLINE of PRESENTATION 1. Strain rates are of great importance for Solid Earth Sciences. Within the EU Horizon 2020 project EPOS-IP WP10 TCS-GNSS (Global Navigation Satellite System - GNSS thematic core services) a series of products focused on strain rates derived from GNSS data is envisaged. 2. In this contribution, we present preliminary results from 452 permanent European GNSS stations, operating until 2017 and processed at UGA-CNRS (Université Grenoble Alpes, Centre National de la Recherche Scientifique). 3. We calculated the strain-rate field using two open-source algorithms recommended by EPOS-IP, namely the VISR (Velocity Interpolation for Strain Rate) algorithm (Shen et al., 2015) and STIB (Strain Tensor from Inversion of Baselines), developed by Masson et al., (2014) as well as the SSPX software suite (Cardozo and Allmendinger, 2009). 4. We compared the results derived from different methods and discuss the similarities and differences. 5. We also validated our results w.r.t literature. 2

3 1. GNSS velocity data EPOS Velocity data (452 permanent stations with data spanning more than 3 years) Processed with DD for positions operating until 2017 by UGA-CNRS, with MIDAS (UNR) for velocities Italy grid LON/LAT: 4.5 E<=lon<=20 E, 35 N<=lat<=48.5 N) 213 stations Greece grid LON/LAT: 19.5 E<=lon<=29 E, 34 N<=lat<=42 N) 20 stations Note The first product is focused on Italy and Greece because of a) magnitude of strain-rate w.r.t rest of Eurasia and b) availability of stations 3

4 GNSS data (left) GNSS stations (red triangles) in Europe, (right) GNSS velocities (ITRF08 frame) in the CNRS MIDAS data 4

5 GNSS Stations Map: Italy (+Alps, Dinarides) (left) GNSS stations (red triangles) in Italy, (right) GNSS velocities in the CNRS MIDAS data 5

6 GNSS Stations Map: Greece (left) GNSS stations (red triangles) in Greece, (right) GNSS velocities in the CNRS MIDAS data 6

7 2a. VISR result: strain-rates in Greece Model Configuration: spatial smoothing Min 1 km Max 500 km Incr. 1 km Dist. Weight: Gaussian Spat. Weight: Voronoi Weight 6 Unc Thresh 0.5 Grid step 0.5 Compression domains (Ionian Sea, N. Aegean Sea) are mapped satisfactorily Compression enters into central Greece which is not justified by seismology/geology extension in central Greece is correct in azimuth but underestimated in magnitude East-west switch is not well resolved 7

8 Model Configuration: spatial smoothing Min. 100 km Max. 500 km Incr. 30 km Dist. Weight Gaussian Spat. Weight Voronoi Weight 6 Unc. Thresh 0.5 Grid step 0.5 strain orientation seems correct strain character seems correct strain magnitude underestimated VISR result: strain-rates in Italy 8

9 Model Configuration: spatial smoothing Min 100 km Max 500 km Incr 30 km Dist Weight Gaussian Spat Weight Voronoi Unc Thresh 0.5 Grid step 0.5 VISR result: strain-rates in Italy influence of Wt increase Left Wt=12, middle Wt=24, right Wt=48 increase of Wt = smoother strain field, compression in the Po valley vanishes 9

10 2b. STIB: main processing parameters Smoothing Distance (e.g. 10km, 30km, 50km, 200km etc.) Grid configurations Europe Min Max Step Longitude Latitude Italy Min Max Step Longitude Latitude Greece Min Max Step Longitude Latitude The STIB approach uses the length variations of the baselines between each pair of the geodetic stations to provide a map of the deformation over the whole area covered by the network, reducing the impact of erroneous data and noise. The computation of the strain rate tensor is obtained by inversion of the variation of the length of all the baselines obtained from the geodetic network. 10

11 STIB result: principal strain-rate axes in Greece grid step of 0.5. Left ) smoothing distance 50 km Right ) smoothing distance 100 km Compression domains (Ionian Sea, N. Aegean Sea) are mapped satisfactorily orientation of extension in central Greece deviated by degrees picked up 90 degrees switch in extension along mainland Greece 11

12 STIB result: principal strain-rate axes in Italy - grid step of 0.5. Left) smoothing distance 30 km Right ) smoothing distance 50 km Extension resolved across the Apennines - compression in the Po valley, Dinarides strain magnitude reasonable ~50 ns/yr Apennines no significant differences between km smoothing distance 12

13 SSPX: main processing parameters Grid configurations Europe Min Max Step Longitude Latitude Italy Min Max Step Longitude Latitude Greece Min Max Step Longitude Latitude

14 SSPX result: principal strain-rate axes in Greece Italy - grid step 43 km. 14

15 Comparison of VISR-SSPX results for Italy (common nodes = 733) Product: Dilatation_Italy (VISR original VISR interpolated at SSPX nodes SSPX) GNSS stations are shown as yellow triangles 15

16 Statistical Comparison of results for Italy (common nodes = 733) VISR parameters are Wt=12, smoothing distances 1-200km Diagonal lines indicate 1:1 fit 16

17 3a. Product Validation - Greece Chousianitis Ganas Evangelidis (2015) result: strain-rate in mainland Greece Floyd et al. (2010) result: principal strain-rate axes in broader Aegean 17

18 3b. Product Validation - Italy Figure 11 D'Agostino (2014) result: principal strain-rate axes in Italy 18

19 3b. Product Validation - Italy 1. A good match exists between the EPOS product and the Quaternary faults which are accommodating the extension in the Calabrian Arc (Calabria + NE Sicily) 2. We have also highlighted where compression is mapped. 3. This compression is the result of the Eurasia and Africa collision and it is "shared" between the SBT and the thrust fault system offshore north of Sicily. 19

20 DOI: /zenodo Principal axes of strain plotted using gmtstrainplot.sh script. Yellow circles show EPOS GNSS sites with their codes 20

21 4. Summary of Preliminary results 1. We presented preliminary results from 452 permanent European GNSS stations, operating until 2017 and processed at UGA-CNRS with DD technique. 2. We calculated the strain-rate field using two open-source algorithms recommended by EPOS-IP, namely the VISR and STIB as well as the SSPX software suite. 3. Overall, our first results reproduce the gross features of tectonic deformation in both Italy and Greece, such as NE-SW extension across the Apennines and N-S extension in Central Greece. 4. It is anticipated that the significant increase of GNSS data amount associated with the operational phase of EPOS in the forthcoming years will be of great value to perform an unprecedented, reliable strain rate computation over the Eurasian plate. 21

22 Thanks! 22