Spatial Heterogeneity of Uplift Pattern in the Western European Alps Revealed by InSAR Time‐Series Analysis

Abstract

The European Alpine belt results from the complex continental collision phases between Africa and Eurasia (Coward & Dietrich, 1989;Schmid & Kissling, 2000). While convergence is still active and is attested by Adria indentation in the Eastern and Central Alps, it stopped in the Western Alps, where the present-day kinematics are characterized by the anticlockwise rotation of Adria microplate with respect to Eurasia (e.g., Calais et al., 2002). Global Navigation Satellite System (GNSS) measurements highlight extensive and transcurrent horizontal strain rates in the western part of the belt, without any measured shortening across it (Calais et al., 2002;Serpelloni et al., 2016Serpelloni et al., , 2018. The dynamic processes that have been suggested to affect the Western Alps involve intrinsic surficial (isostatic adjustments to deglaciation and erosion) and deep sources (slab pull or break-off and mantle upwelling), as well as far-field microplate kinematics, but their respective contributions to present-day crustal deformation are an ongoing debate (e.g., Sternai et al., 2019).GNSS and leveling measurements in the Western Alps indicate that vertical velocities of a few mm/yr are expected, which is an order of magnitude higher than the horizontal motions (

Swarms and mainshock–aftershocks sequences are both triggered by fluids in the Ubaye Region (Western Alps)

“…Similar stress-states have been reconstructed for the last swarms (2003-2004 and 2012-2015) occurring in the Ubaye Region (Leclère et al 2013;Fojtíková and Vavryčuk, 2018). Focal mechanisms of the largest events are from several catalogues: Fréchet and Pavoni (1979), Leclère et al (2013), Thouvenot et al (2016), FMHex20 (Mazzotti et al 2021) and Mathey et al (2021a). Their colours show the depth of the events.…”

“…Thereafter, we gathered all the available focal mechanisms in a catalogue (full Ubaye Region catalogue). This catalogue is composed of the FMHex20 catalogue from Mazzotti et al (2021), mechanisms from Fréchet and Pavoni (1979), Leclère et al (2013), Thouvenot et al (2016), and Mathey et al (2021a). In total, 799 focal mechanisms composed the full Ubaye Region catalogue, those with a magnitude larger than ML LDG 3.4 (4% of the events) are displayed in Fig.…”

“…For this sequence, only 3 focal mechanisms were already computed (Thouvenot et al 2016;Mathey et al 2021a). We choose to refine the analysis by computing the focal mechanisms of the largest events in the relocated catalogue of De Barros et al, 2019. In total, 15 seismic stations were used: 7 from the temporary network and 8 permanent ones (3 from the INGV network (University of Genoa., 1967;INGV Seismological Data Centre, 2006); 5 from the RESIF network (RESIF, 1995)).…”

Referencing of Continental‐Scale InSAR‐Derived Velocity Fields: Case Study of the Eastern Tibetan Plateau

“…Other hydrological signals are also apparent in both the cosine and sine maps, especially within catchment basins or at the foothills of mountains ranges in desert areas. The cosine maps also display strong residual tropospheric delays with pronounced phase‐elevation relationships in deeply incised valleys of southeastern Tibet where the ERA‐5 atmospheric correction is not accurate (Mathey et al., 2022). An in‐depth analysis of the seasonal pattern is beyond the scope of the present paper.…”

Imaging the Spatiotemporal Evolution of Plate Coupling With Interferometric Radar (InSAR) in the Hikurangi Subduction Zone

“…We use the NSBAS (New Small BAseline Subset) processing chain to process the interferograms that are then unwrapped and inverted to obtain a time series that captures the evolution of surface displacement (Thollard et al., 2021). To ensure robust estimates of the surface displacement time series and minimize potential biases linked to soil moisture and agricultural vegetation, we construct the interferogram network using a combination of short and long‐temporal baselines (Dodds et al., 2022; Mathey et al., 2022). To enhance the signal‐to‐noise ratio, we multi‐look the interferograms with a window size of 64 pixels in range and 16 pixels in azimuth, resulting in a spatial resolution of approximately 160 m × 240 m. Tropospheric signals are mitigated using the ERA‐5 reanalysis weather model before unwrapping.…”