This technical report presents preliminary analysis results from two GNSS stations near the epicenter of large earthquakes in Thessaly, Greece on March 3rd and 4th, 2021. The earthquakes were magnitudes 6.0 and 5.9. Analysis of data from stations KLOK and LARM found permanent displacements of -4.0cm east and -2.7cm north at KLOK and 0.4cm east and 0cm vertical at LARM due to the earthquakes. More detailed analysis is still underway to better estimate the offsets.

1. NATIONAL TECHNICAL UNIVERSITY OF ATHENS
DIONYSOS SATELLITE OBSERVATORY
HIGHER GEODESY LABORATORY
Preliminary analysis results for continuous GNSS stations at Thessaly (3 & 4/03/2021)
Dr. Dimitris Anastasiou, Xanthos Papanikolaou
This technical report dated 9 March 2021 presents preliminary results obtained from the analysis of
GNSS stations available in the region of Thessaly and near the epicenter of the large earthquakes
sequence that took place place on the 3rd
and 4th
of March 2021.
The earthquake sequence was dominated by two large earthquakes; information on these events are
presented in the following table, as provided by the National Observatory of Athens (see
http://www.gein.noa.gr/services/full_catalogue.php)
Date Time
(GMT)
Latitude
(degrees)
Longtitude
(degrees)
Depth
(km)
Magnitude
(local)
2021 MAR 3 10 16 08.3 39.7591 22.2102 8 6.0
2021 MAR 4 08 38 19.1 39.7993 22.1260 5 5.9
30s GNSS data analysis
Dionysos Satellite Observatory routinely processes GPS/GNSS data from continuous stations around
Greece. The core of this processing engine is Bernese GNSS Software, version 5.2 [1].
Two stations are of special interest, located close enough the epicenter of the earthquakes that could be
displaced at a level identifiable by GPS/GNSS analysis. These are KLOK
(http://geodesy.gein.noa.gr:8000/nginfo/klok/), included in GEIN’s NOANET network and LARM
(https://epncb.oma.be/_networkdata/siteinfo4onestation.php?station=LARM00GRC) which is a
European Permanent Network (EPN) site. We present time-series results obtained at DSO for the two
aforementioned stations, for the time interval relevant to the earthquake sequence.
The depicted time series plots, present the time period from station installation date up today.
The permanent displacements observed, are presented in the following table. Note that:
1. the displacement presented here, is the accumulated displacement of the earthquake sequence,
2. the offsets are computed as the difference between the relevant values in the past 10 days and
the three days following the events, aka the 5th
, 6th
and 7th
of March,
3. ultra-radip products and forecast Numerical Weather Model (NWM)[2] products were used to
estimated coordinates for the days of the earthquake sequence,
4. vertical (Up) displacements are statistically insignificant; a safer estimation could be made
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2. using the whole data span of the sites, taking into account harmonic signals,
5. as noted, these are preliminary results; more reliable offset estimates will be made at a latter
stage, as the post-seismic sequence degrades and we have more data at our disposal.
Station Region dN(cm) dE(cm) dU(cm)
KLOK Klokotos -4.0 -2.7 0.2
LARM Larisa 0.4 0.0 0.0
References
[1] Dach, R., U. Hugentobler, P. Fridez, and M. Meindl (2007), Bernese gps software, version 5.0, Jet.
Propul. Lab., Astronomical Institute, University of Bern.
[2] re3data.org: VMF Data Server; editing status 2020-12-14; re3data.org - Registry of Research Data
Repositories. http://doi.org/10.17616/R3RD2H
Note: This document will be under constant update; any interested parties are kindly requested to
contact DSO for further results.
Contact Info
Dionysos Satellite Observatory
dso@survey.ntua.gr
Dr. Demitris Anastasiou, Adjunct Lecturer UniWA
dganastasiou@gmail.com
Xanthos Papanikolaou, PhD Candidate NTUA
xanthos@mail.ntua.gr
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3. Station KLOK
3

4. Station LARM
4

5. Preliminary results for GNSS stations displacements
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