The contribution of space geodetic techniques to interseismic velocity estimation, and thus seismic hazard
modelling, has been recognized since two decades and made possible in more recent years by the increased availability
and accuracy of geodetic measurements. We present the preliminary results of a feasibility study performed within the
CHARMING project (Constraining Seismic Hazard Models with InSAR and GPS), funded by the European Space Agency
(ESA). For a 200 km x 200 km study area, covering the Abruzzi region (central Italy) we measure the mean surface
deformation rates from Synthetic Aperture Radar and GPS, finding several local to regional deformation gradients
consistent with the tectonic context. We then use a kinematic finite element model to derive the long-term strain rates, as
well as earthquake recurrence relations. In turn these are input to state-of-the-art probabilistic seismic hazard models, the
output of which is validated statistically using data from the Italian national accelerometric and macroseismic intensity
databases.Published373-3773T. Pericolosità sismica e contributo alla definizione del rischioN/A or not JCRope

Atzori, S.

Berardino, P.

Carafa, M. M. C.

D'Amico, V.

Devoti, R.

Fornaro, G.

Kastelic, V.

Meletti, C.

Merryman Boncori, J. P.

Pezzo, G.

Pietrantonio, G.

Riguzzi, F.

Salvi, S.

Visini, F.

English

Earth-prints

6th International INQUA Meeting on Paleoseismology, Active Tectonics and Archaeoseismology,  
19-24 April 2015, Pescina, Fucino Basin, Italy 
 
 
INQUA Focus Group on Paleoseismology and Active Tectonics 
 
 
 
Interseismic ground velocities of the Central Apennines from GPS and SAR measurements and 
their contribution to seismic hazard modelling: preliminary results of the ESA CHARMING 
project  
 
Pezzo, G.(1), Merryman Boncori, J.P. (1), Visini, F. (2), Carafa, M.M.C. (3), Devoti, R. (1), Atzori, S. (1), Kastelic, V., (3), Berardino, P. (4), Fornaro, G. 
(4), Riguzzi, F. (1), Pietrantonio, G. (1), D’Amico, V. (2), Meletti, C. (2), and Salvi, S. (1) 
 
(1) Istituto Nazionale di Geofisica e Vulcanologia (INGV), Centro Nazionale Terremoti, Via di Vigna Murata 605, 00143 Roma, Italy, 
(2) Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Pisa, Via della Faggiola 32, 56126 Pisa, Italy, 
(3) Istituto Nazionale di Geofisica e Vulcanologia (INGV), Tettonofisica e Vulcanologia, Via dell’Arcivescovado 8, 67100 L'Aquila, Italy, 
(4) Istituto per il Rilevamento Elettromagnetico dell’Ambiente (IREA) del Consiglio Nazionale delle Ricerche (CNR), Via Diocleziano 328, 
80124 Napoli, Italy. 
 
Abstract: The contribution of space geodetic techniques to interseismic velocity estimation, and thus seismic hazard 
modelling, has been recognized since two decades and made possible in more recent years by the increased availability 
and accuracy of geodetic measurements. We present the preliminary results of a feasibility study performed within the 
CHARMING project (Constraining Seismic Hazard Models with InSAR and GPS), funded by the European Space Agency 
(ESA). For a 200 km x 200 km study area, covering the Abruzzi region (central Italy) we measure the mean surface 
deformation rates from Synthetic Aperture Radar and GPS, finding several local to regional deformation gradients 
consistent with the tectonic context. We then use a kinematic finite element model to derive the long-term strain rates, as 
well as earthquake recurrence relations. In turn these are input to state-of-the-art probabilistic seismic hazard models, the 
output of which is validated statistically using data from the Italian national accelerometric and macroseismic intensity 
databases. 
 
Key words: Active Tectonics, Seismic Hazard, SAR, GPS 
 
Introduction 
The CHARMING project (Constraining Seismic Hazard 
Models with InSAR and GPS) is a feasibility study funded 
by the European Space Agency's (ESA) Support to 
Science Element (STSE) Pathfinders 2013 programme. 
The context of CHARMING is Probabilistic Seismic Hazard 
Assessment (PSHA), i.e. the scientific field which aims to 
quantify the probability that ground motion at a 
specified site will exceed some level of a given shaking 
parameter of engineering interest  (e.g. Peak Ground 
Acceleration, PGA) during a specified future time frame 
The main aim of the project is to investigate whether 
surface deformation measurements, derived from GPS 
and Synthetic Aperture Radar (SAR) data, can be 
successfully incorporated into PSHA models and 
improve their quality. In particular, we investigate 
several aspects related to the marginal benefit provided 
by the integration of SAR compared to GPS alone, since 
to our best knowledge this project represents the first 
attempt worldwide to incorporate SAR measurements 
into PSHA models. 
The areas of interest analyzed within the project include 
a large portion of central and southern Italy. A restricted 
development area, comprising the central Abruzzi 
region, is used for technique developement and 
validation. At a later stage the developed methods shall 
be applied to a wider experimental area (larger rectangle 
in Fig. 1). For these areas we generate interseismic 
velocity maps, using a combination of ~100 permanent 
GPS stations (Fig. 1) and measurements derived from 
coast-to-coast acquisitions of the ERS-1/2 AMI, ENVISAT 
ASAR and ALOS PALSAR satellite SAR sensors (Fig. 2). The 
geodetic measurements are screened to exclude 
contributions of non-tectonic origin (e.g. subsidence). 
Subsequently, a kinematic finite element model and a 
tapered Gutenberg-Richter model are applied to the 
mean velocity measurements to derive long term strain 
rates and earthquake rates, i.e. the number of 
earthquakes in a given time period above an established 
magnitude threshold, Finally, state of the art PSHA 
modelling techniques are used to generate probabilistic 
models for PGA and other shaking parameters. A 
statistical validation of the PSHA model output is carried 
out, using data from national accelerometric and 
macroseismic intensity databases. 
 
 
 
Figure 1: GPS stations and networks within the 
development (smaller) and experimental (larger) areas 
(dashed blue rectangles). Orange polygons represent 
composite and individual seismogenic sources according to 
the DISS v.3.1.1 catalogue (Working Group, DISS 2010). 
Yellow stars represent major earthquakes (Mw > 5.0), 
occurred since 1992. 
6th International INQUA Meeting on Paleoseismology, Active Tectonics and Archaeoseismology,  
19-24 April 2015, Pescina, Fucino Basin, Italy 
 
 
INQUA Focus Group on Paleoseismology and Active Tectonics 
 
 
 
 
Figure 2: Spatial (top) and temporal (bottom) coverage for (A) ERS-1 and ERS-2 SAR ascending tracks, (B) ENVISAT ASAR 
descending tracks acquired with Imaging Swath 2 (IS2), and (C) ALOS PALSAR Fine Beam Single and Dual ascending tracks. 
See the caption of Fig. 1 for other plot features. 
 
Geodetic data and methods 
GPS data were processed with the method of Devoti et 
al., (2014) to obtain mean deformation rates. Only 
stations with >3 years of observations were retained. For 
the stations in the epicentral area of the the Mw 6.3 2009 
L'Aquila earthquake, measurements were truncated to 
Dec. 31. 2008.  
SAR image processing was performed with the 
combined Persistent Scatterer and Small Baseline 
approach of (Hooper et al., 2008), implemented in the 
StaMPS (Stanford Method for Persistent Scatterers) 
software. One of the tracks (ENVISAT 308 descending) 
was independently processed with the Small Baseline 
Subset (SBAS) technique of (Berardino et al., 2002). 
Ascending and descending passes of the ENVISAT and 
ERS-1/2 satellites and ascending passes of the ALOS 
PALSAR sensor (Fig. 2) were processed to derive SAR 
line-of-sight (LoS) deformation rate maps. These were 
then calibrated with GPS measurements, projected onto 
the LoS, to ensure a common reference frame and to 
correct residual long-wavelength errors in the SAR 
measurements arising from atmospheric propagation, 
orbital uncertainties and other sources (Marinkovic and 
Larsen, 2013). East and Up Cartesian deformation 
components can be derived in regions of overlap 
between at least one ascending and one descending 
SAR acquisition. 
In the project's development phase, two experimental 
approaches are also investigated. The first consists in the 
application of the Intermittent SBAS (ISBAS) approach 
(Sowter et al., 2013), which can potentially provide a 
significant increase in the coverage of the LoS 
measurements. The second is based on a multi-temporal 
extension of the Spectral Diversity or Multi Aperture 
InSAR (MAI) technique (Scheiber and Moreira, 2000; 
Bechor & Zebker 2006), and could potentially provide a 
high sensitivity also to the flight-path (~N-S) 
deformation component. 
 
Discussion 
Within the development area, the mean deformation 
rates from GPS and SAR show in general an excellent 
level of agreement. An example is shown in Fig. 3, for 
ENVISAT ASAR descending track 36, for which the 
differences show a standard deviation of 1.5 mm/year in 
the SAR LoS (Fig. 4). Our preliminary results also 
exemplify the complementarity of these two 
measurement techniques in the Central Apennines. 
While the GPS is essential to constrain the long-
wavelength patterns (>30 km), the SAR can potentially 
"fill in the gaps" between GPS measurements, thus 
defining more clearly the spatial extent of features and 
the location of transition zones.  
  
 
Figure 3: (A) Mean LoS from ENVISAT descending track 36 
and (B) from GPS projected onto the SAR LoS. Positive and 
negative values indicate motion towards and away from the 
radar respectively. Measurements are referred to the 
location of the TRIV station. SAR velocities represent an 
average of measurements in a 1 km radius from the GPS 
stations.  
 
A preliminary analysis of the GPS data highlights several 
signals ascribable to the local tectonics. The GPS vertical 
component (Fig. 5A) shows an overall NW-SE oriented 
uplift along the central Apennines from 0.5 to more than 
2 mm/yr. This long-wavelength velocity pattern could be 
attributed to the general NE-SW oriented extension of 
the Apennines chain (D'Agostino et al., 2001). Some local 
subsiding stations are also recognized, namely SMRA, 
6th International INQUA Meeting on Paleoseismology, Active Tectonics and Archaeoseismology,  
19-24 April 2015, Pescina, Fucino Basin, Italy 
 
 
INQUA Focus Group on Paleoseismology and Active Tectonics 
 
 
 
CHIE, LPEL and VTRA. For the latter three, the subsidence 
is likely to be very local. However, the SMRA subsidence, 
possibly associated to the combined action of sediment 
compaction and ground water pumping, appears to 
have a larger spatial scale in the SAR measurements (Fig. 
3A), so that a tectonic contribution cannot be entirely 
excluded.  
 
 
 
Figure 4: Scatter plot of InSAR (descending ENVISAT track 
36) and GPS velocities (projected along the SAR LoS).  
 
The GPS east and north velocities (Fig. 3A and 3B) show a 
regional pattern broadly consistent with the NE-SW 
Apenninic extension. At a more local scale however, we 
observe interesting velocity gradients between the 
ALRA, RMI2, CERA and ISER GPS stations, in the area 
north and east of PBRA and north INGP station. In the 
first case a > 1 mm/yr extension between the SORA-
BLRA-VVLO-OTRA block, with respect to the ALRA-RNI2-
CERA one, can be detected. The same area shows 
shortening velocity gradients in the GPS North 
component (> 1 mm/yr), resulting in a general NE-SW 
oriented left-lateral deformation zone located between 
the Matese mountains, to the south, and the Marsica 
ones, to the north. Although the processed SAR data is 
not centred on this area, the resulting LoS velocity map 
(Fig. 3A) seems to show similar deformation patterns. 
North of PBRA station, we observe two blocks (PBRA-
LPEL and ATRA-PSAN) moving eastward more quickly 
(from 1 to > 2 mm/yr) than CDRA-OVRA, SCRA-MANO 
and CHIE-FRRA blocks. In the same areas, for the North 
component, a N-S shortening (~ 1 mm/yr) between the 
PBRA-MANO-CDRA-OVRA block and the CHIE-FRRA-
PSAN-ATRA one can be detected. Thus, the resulting 
deformation pattern is a NE movement of the Maiella 
mountain zone (PBRA-LPEL) with respect to the Chieti 
(CHIE) one (i.e. a shortening) and a northward 
movement of the Gran Sasso zone (CDRA) with respect 
to the Chieti one, resulting in a general NE-SW oriented 
extension. SAR velocities seem compatible with these 
patterns, even though further processing of all adjacent 
tracks from all sensors is needed to confirm these trends. 
 
Figure 5: UP (A), East (B) and North components of the 
GPS velocities from Devoti et al. (2014), development area 
(purple rectangle) and DISS catalogue seismic sources. 
 
Another interesting velocity gradient concerns the NE 
part of the development area, in which the MTER-MTRA 
block is moving westward (~1 mm/yr) and southward 
(~2 mm/yr) with respect the MTTO-INGP-AQUI block, 
which shows eastward and northward movements. 
These velocities result in a left-lateral deformation zone 
located north of L'Aquila (AQUI), where some seismic 
sources give place to others to the north. This structural 
setting is very similar to that of the southern side of the 
development area, near the CERA station, where we also 
observe a southward interruption of the main seismic 
sources, which give place to other structures. Moreover, 
comparing the GPS data distribution with historical data 
(Rovida et al., 2011) and seismological data 
(http://iside.rm.ingv.it) in the timespan of the geodetic 
6th International INQUA Meeting on Paleoseismology, Active Tectonics and Archaeoseismology,  
19-24 April 2015, Pescina, Fucino Basin, Italy 
 
 
INQUA Focus Group on Paleoseismology and Active Tectonics 
 
 
 
measurements (1992-2008 period), it is apparent that in 
both time intervals these two deforming areas are 
characterized by an intense seismic activity with respect 
to adjacent ones, thus strengthening a possible tectonic 
interpretation (Fig. 6). 
 
 
Figure 6: Historical (Rovida et al., 2011) and instrumental 
seismicity (1992-2008 period) (http://iside.rm.ingv.it), 
development area (purple rectangle) and DISS catalogue 
seismic sources. 
 
A preliminary model run was carried out on the GPS data 
alone, within the development area of interest. We built 
a finite element model to derive long term average 
velocity fields accounting for the main tectonic features 
of the study area. From this model, we then calculated 
the earthquake rates, i.e. the number of earthquakes in a 
given time period above an established magnitude 
threshold, following the Seismic Hazard Inferred From 
Tectonics (SHIFT) approach (Bird and Liu, 2007; Carafa 
and Kastelic 2014). Finally, state of the art PSHA 
modelling techniques were used to generate 
probabilistic models for horizontal peak ground 
acceleration (PGA) and other shaking parameters. Our 
preliminary results, in terms of PGA with 10% probability 
of exceedance in 50 years on hard ground (Fig. 7), show 
that expected PGA exceeding 0.2g characterize large 
part of Apennines and, in particular, two areas have the 
highest level of hazard with values exceeding 0.4g. 
 
 
 
Figure 7: Seismic hazard map showing the PGA distribution 
with 10% probability of exceedance in 50 years, computed 
on hard ground (VS30 > 800 m/s) and using the Akkar et al. 
(2014) ground motion model. 
A statistical validation of the PSHA model output was 
carried out using data from the national accelerometric 
and macroseismic intensity databases. Our first results 
suggest that our model is not rejected by the 
observations, thus supporting the viability of our 
approach for seismic hazard purposes. 
 
 
Acknowledgements: GP and JPMB were funded by the 
European Space Agency - INGV CHARMING project. FV, MMCC, 
VK were funded by the Abruzzo Project, code: 
RBAP10ZC8K_003, funded by the Italian Ministry of University 
and Research (MIUR). Some of the figures were prepared using 
the public domain GMT software (Wessel & Smith, 1998). 
 
 
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Interseismic ground velocities in Central Apennines from GPS and InSAR measurements: new contributions for seismic hazard models by preliminary results of ESA CHARMING project

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Interseismic ground velocities in Central Apennines from GPS and InSAR measurements: new contributions for seismic hazard models by preliminary results of ESA CHARMING project

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