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Annex B: Kefalonia (data processing report)

Surface displacement due to the 2014/02/03 Kefalonia earthquake - INGV/NOA working notes
Processed data

Date (YYYYMMDD)	Time	Sensor	Pass	Beam	Incidence angle (°)
20140202	16:31	CSKS1	Desc	H4-08	38
20140210	16:31	CSKS2	Desc	H4-08	38
20140128	16:23	TDX-1	Asc	-	22
20140208	16:23	TDX-1	Asc	-	22

Tab. SAR acquisitions used in this study.

Id	Date-1 (YYYYMMDD)	Date-2 (YYYYMMDD)	Pass	Beam	Btemp (days)	Bperp (m)	Dfdc (Hz)
I1	20140202	20140210	Desc	H4-08	8	320	-47
I2	20140128	20140208	Asc	-	11	108	-73

Tab. InSAR pairs used in this study. The last three columns indicate the temporal, spatial (perpendicular) baselines and the difference in Doppler centroid.
Area of interest


Fig. Map of Kefalonia adapted from Karymbalis et al., 2013. Black rectangle shows area of interest for SAR displacement plots in this document.

Coseismic deformation patterns

Deformation patterns are shown in the radar line-of-sight (LoS), considered positive from ground to satellite, and in the flight-path (azimuth) direction. In the following we comment on the patterns observed in three different areas, denoted as Sectors 1, 2 and 3 in Fig. (top-left). The fault traces sketched in the plots are discussed in the "Preliminary Interpretation" section. East, North, and Up components were derived through a weighted least sware inversion of all the LoS and azimuth measurements, accounting for the spatially varying heading and incidence angles.

Fig. InSAR phase coherence magnitude (left) and wrapped phase (right). Top row: I1 (COSMO-SkyMed). Bottom row: I2 (TanDEM-X).

Sector 1

In the descending LoS, measured with DInSAR (Fig. , left) and offset tracking (Fig. , left), negative values up to -19 cm, compatible with susidence and/or westward motion, are observed close to the right-lateral fault trace. The LoS displacement reaches zero or slightly positive values at the edge of the plotted area (max. 2 cm in the southeastern corner).

In the descending azimuth, measured with MAI (Fig. , right) and offset tracking (Fig. , right), positive values are observed, compatible with a southward motion component. The spatial variations of this deformation, mimic that of the LoS component, with higher values close to the right-lateral fault trace, at the tip of the Gulf of Argostoli, gradually decreasing to zero at the borders of the area of interest.

In the ascending LoS, measured with DInSAR (Fig. , left) offset tracking (Fig. , left), negative values up to -7 cm, compatible with subsidence and/or eastward motion, are observed close to the right-lateral fault trace. Compared to the descending LoS, a different spatial variation pattern is observed (cfr. also wrapped DInSAR interferograms in Fig. ), in which zero values are reached already in a radius of 5 km from the right-lateral fault trace, and maintained within the rest of the area of interest. Many areas are masked out due to layover on several slopes, favoured by the steep TD-X incidence angle (Tab. ).
In the ascending azimuth, measured with MAI (Fig. , right) offset tracking (Fig. , right), negative values are observed, compatible with a southward motion component, in agreement with the descending azimuth results.
The East, North, Up components, Fig. , reveal that this sector is undergoing a southward motion and a compression, characterized by westward motion and subsidence.
Sector 2

In the descending LoS, measured with DInSAR (Fig. , left) and offset tracking (Fig. , left), from north to south, three different patterns are observed: in the northmost part of the sector DInSAR yields an almost zero motion, whereas offset tracking shows a slightly positive one, compatible with a moderate uplift and/or eastward motion. Moving southwards, DInSAR measures moderate negative values of -4 cm, compatible with a moderate subsidence and/or westward motion. Finally, further to the south, both DInSAR and offset tracking show a positive gradient towards the border with Sector 3, compatible with an increasing uplift and/or eastward motion.
In the descending azimuth, measured with MAI (Fig. , right) and offset tracking (Fig. , right), negative values are observed in the northern and central part of the sector, indicating a northward motion component. Towards the south-west, the deformation tends to zero, whereas at the border with Sector 3 a discontinuity is observed, with a transition to positive values, compatible with southward motion.

In the ascending LoS, measured with DInSAR (Fig. , left) and offset tracking (Fig. , left), moderate positive values are observed in the northmost part of the sector, compatible with uplift and/or westward motion. In the central portion of the sector the positive values reach their maximum at the border with Sector 1. Further south, towards the border with Sector 3, values first decrease (green) and then increase again (blue), always remaining positive.
In the ascending azimuth, measured with MAI (Fig. , right) offset tracking (Fig. , right), positive values are observed, indicating a northward motion component, in agreement with the descending azimuth results. At the border with Sector 3 a discontinuity is observed, associated with a transition towards negative values, indicating a southward motion component. Also this is in agreement with the descending azimuth results.
The East, North, Up components, Fig. , reveal that this sector is undergoing a northward motion and an uplift, as well as a generally moderate westward motion, which however reaches higher values in a central latitude band.
Sector 3

In the descending LoS, measured with DInSAR (Fig. , left) and offset tracking (Fig. , left), positive values up to 13 cm are observed, with the peak displacement falling about 3 km north-west of Lixouri. This is compatible with an uplift and/or an eastward motion.
In the descending azimuth, measured with MAI (Fig. , right) and offset tracking (Fig. , right), positive values are observed, indicating a southward motion component.

In the ascending LoS, measured with DInSAR (Fig. , left) aand offset tracking (Fig. , left), positive values are observed, compatible with uplift and/or westward motion. The peak is slightly shifted compared to the descending LoS results.
In the ascending azimuth, measured with MAI (Fig. , right) offset tracking (Fig. , right), negative values are observed, indicating a southward motion component, in agreement with the descending azimuth results.
The East, North, Up components, Fig. , reveal that this sector is undergoing a an eastward motion and an uplift, as well as a southward motion.

Fig. Left: I1 (COSMO-SkyMed) DInSAR Line of Sight displacement. Positive values indicate motion towards the satellite (i.e. uplift and/or eastward motion). Right: Multi Aperture Interferometry azimuth displacement. Positive values indicate motion in the satellite flight path (i.e. approx. southward).

Fig. Left: I2 (TanDEM-X) DInSAR Line of Sight displacement. Positive values indicate motion towards the satellite (i.e. uplift and/or westward motion). Right: Multi Aperture Interferometry azimuth displacement. Positive values indicate motion in the satellite flight path (i.e. approx. northward).

Fig. Left: I1 (COSMO-SkyMed) Offset tracking Line of Sight displacement. Positive values indicate motion towards the satellite (i.e. uplift and/or eastward motion). Right: Offset tracking azimuth displacement. Positive values indicate motion in the satellite flight path (i.e. approx. southward).

Fig. Left: I2 (TanDEM-X) Offset tracking Line of Sight displacement. Positive values indicate motion towards the satellite (i.e. uplift and/or westward motion). Right: Offset tracking azimuth displacement. Positive values indicate motion in the satellite flight path (i.e. approx. northward).

Fig. Top left: East displacement component. Top right: North displacement component. Bottom left: Up displacement component. Arrows indicate the magnitude and direction of the horizontal (East and North) displacement components.

Preliminary interpretation
The observed deformation patterns present 3 main discontinuities:

• 
  N-S discontinuity: observed in all LoS and azimuth maps between the Gulf of Myrtos and the Gulf of Argostoli. This discontinuity curves slightly towards north-east, so that overall it is well approximated by two linear segments, as shown in the plots.
  
• 
  NW-SE discontinuity: observed in ascending and descending azimuth deformation maps. The LoS maps do not show a clear discontinuity, but rather a spatial gradient with the same orientation. However local discontinuities with this orientation can also be found in the wrapped InSAR phases (cfr. Fig. top-right, where the NE-SW line intersects the southern coast of the Paliki peninsula).
  
• 
  NNW-SSE discontinuity: running almost parallel to the Gulf of Argostoli. Across the Gulf there is a clear change in fringe density in ascending and descending wrapped interferograms, as well as a sign inversion in the unwrapped LoS displacement maps.
  

Among the faults compatible with the geology of the area, the following 3 would appear to explain these discontinuities as well as the main deformation patterns:

Structure 1: an almost N-S oriented structure, approximated by two linear segments in the figures, west-dipping and with a mainly right-lateral mechanism, with a small inverse component. Sector 1 would therefore be the footwall, and Sector 2 the hanging wall of this fault. This is compatible with the focal solution from NOA concerning the mechanisms, although quite different strike and dip values are found (NOA moment tensor solutions: strike = 13°/108°, dip = 75°/73°, rake = 168°/15°). Geologically, this structure would be mostly under the Paliki peninsula, rather than being a north continuation of the east-dipping thrusts in the southern part of the island, running parallel to the Argostoli peninsula in Fig. .
Structure 2: a NE-SW oriented fault, near-vertical, with a main right-lateral mechanism. It is possible for this to be a transfer fault zone. Interestingly the orientation of this structure would be compatible with the focal mechanism of the 26 Jan. event. Also, it would have a similar orientation compared to the Kefalonia Transform Fault.
Structure 3: an almost N-S fault, west dipping, with a predominant thrust component. This would explain the uplift and easward motion components, Fig. . The possibility of such faults in this area would seem confirmed by the presence of other east-verging thrusts (Fig. ). However the link of this structure to Structure 1 is unknown and so is its exact position, due to water. The fringe density of the wrapped descending interferogram (Fig. , top-right), suggests however a greater proximity to Paliki.

Fig. Geological map of Kefalonia from Underhill, 2006.

Annex C: Pezzo et al., 2014 - Baluchistan (Accepted)