An Analysis of Vertical Crustal Movements along the European Coast from Satellite Altimetry, Tide Gauge, GNSS and Radar Interferometry

The main aim of the article was to analyse the actual accuracy of determining the vertical movements of the Earth’s crust (VMEC) based on time series made of four measurement techniques: satellite altimetry (SA), tide gauges (TG), fixed GNSS stations and radar interferometry. A relatively new issue is the use of the persistent scatterer InSAR (PSInSAR) time series to determine VMEC. To compare the PSInSAR results with GNSS, an innovative procedure was developed: the workflow of determining the value of VMEC velocities in GNSS stations based on InSAR data. In our article, we have compiled 110 interferograms for ascending satellites and 111 interferograms for descending satellites along the European coast for each of the selected 27 GNSS stations, which is over 5000 interferograms. This allowed us to create time series of unprecedented time, very similar to the time resolution of time series from GNSS stations. As a result, we found that the obtained accuracies of the VMEC determined from the PSInSAR are similar to those obtained from the GNSS time series. We have shown that the VMEC around GNSS stations determined by other techniques are not the same.

Slow earthquake signatures in the ratio between acoustic and internal gravity wave amplitudes in coseismic ionospheric disturbances

<p>Frequency spectra of seismic waves from a fault rupture reflects the size of the faults, i.e. relatively large amplitudes of long period waves are excited by larger earthquakes. Anomalies in rise times of the fault movements would also influence the spectra. For example, earthquakes characterized by slow faulting, known as tsunami earthquakes, excite large tsunamis for the amplitudes of short-period seismic waves. In this study, we compare amplitudes of long- and short-period atmospheric waves excited by vertical crustal movements associated with earthquake faulting. Such atmospheric waves often reach the ionospheric F region and cause coseismic ionospheric disturbances (CID) observed as oscillations in ionospheric total electron content (TEC), with ground Global Navigation Satellite System (GNSS) receivers. CID often includes long-period internal gravity wave (IGW) components in addition to short period acoustic wave (AW) components. The latter has a period of ~4 minutes and propagate by 0.8-1.0 km/s, while the former has a period of ~12 minutes and propagate as fast as 0.2-0.3 km/s. Here we compare amplitudes of these two different waves for five earthquakes, 2011 Tohoku-oki (Mw9.0), 2010 Maule (Mw8.8), 1994 Hokkaido-Toho-Oki (Mw8.3), 2003 Tokachi-oki (Mw8.0), and the 2010 Mentawai (Mw7.9) earthquakes, using data from regional dense GNSS networks. We found two important features, i.e. (1) larger earthquakes show larger IGW/AW amplitude ratios, and (2) Mentawai earthquake, a typical tsunami earthquake, exhibits abnormally large IGW amplitudes relative to AW amplitudes. These findings demonstrate that earthquakes with longer durations for faulting, or with longer times for vertical crustal movements, excite longer period atmospheric waves such as IGW more efficiently.</p>

In search of marine terraces from Central Dobrogea (Casimcea Plateau, Western Black Sea). Preliminary inquires on distribution, extension and vertical crustal movements

Casimcea Plateau is an uplifted (exhumated) peneplain cut in Proterozoic green–schists and one of the oldest tec­tonic units around the Black Sea. Despite its overall monotonous physiognomy, the plateau is crossed by Casimcea Valley and presents a seaward façade to the east which preserves (sub)horizontal surfaces as testimonies of the paleoenvironmental changes (sea level and climate). This research aims to identify the marine and fluvio–marine terraces and to define their vertical distribution based on the morphometric analysis of two study sites (north – Ceamurlia; south – Tașaul Lake) using EU-DEM. 6 levels were identified as possible marine terraces within the 2–50 m altitude range and also some inferences were made concerning the age of the lower three levels. Also, the present work highlights a differential (stronger) uplift of the northern sector between Peceneaga – Camena and Ostrov – Sinoe faults reflected by both the elevation difference of 5–6 m between the terraces staircases identified at the two sites and by the elevation gaps analysed on an array of cross-fault transects carried on over Ostrov – Sinoe fault.

Conflation of satellite altimetry and tide gauge records at coast

This study demonstrates that absolute (geocentric) and relative sea level trends, sea level acceleration, low frequency sea level variations and linear trends in vertical crustal movements experienced at a tide gauge station can be estimated simultaneously using conflated satellite altimetry and tide gauge measurements without the aid of GPS measurements. The formulation is the first of its kind in sea level studies and its effectiveness is exemplified using tide gauge, and satellite altimetry measurements carried out in the vicinity of a tide gauge station.

Space geodetic study of the 2019 typhoon Hagibis: PWV and crustal subsidence

<p>Strong typhoons hit the Japanese Islands repeatedly in 2019. Here we study one of these typhoons (2019 #19 Hagibis 915 hPa, 86 casualties) that landed central Japan on Oct.12 (local time) during the Rugby World Cup tournament, using two different space geodetic approaches, i.e. water vapor and crustal deformation. The first approach is the recovery of Precipitable Water Vapor (PWV) using the zenith wet delays (ZWD) estimated by the dense GNSS array in Japan GEONET. Because atmospheric water vapor concentrates in relatively low altitudes, high humidity is often difficult to recognize in ZWDs when the surface altitude is high. To overcome the difficulty, we reconstructed ZWDs, converted to sea-level values, by spatially integrating the tropospheric delay gradient (azimuthal asymmetry of water vapor) vectors. We also calculated convergence of such delay gradients, equivalent to water vapor convergence index (WVCI) proposed by Shoji (2013 Jour. Met. Soc. Japan). We found that very strong rainfall occurs in the region where both reconstructed ZWD and the delay gradient convergence index are high. Next, we studied vertical crustal movements associated with the water load brought by the typhoon, using the two solutions of the GEONET station coordinates, one from the official F3 solution and the other from the UNR data base. We confirmed subsidence down to ~2 cm in multiple regions where severe flood occurred. Such subsidence was observed to recover with a time constant of 1-2 days reflecting rapid drain of rain water to ocean due to large topographic slope and proximity to the sea. We could not identify, however, crustal uplift due to the low atmospheric pressure at the center of the typhoon.</p>

VERTICAL MOVEMENTS OF THE COAST AND SHELF OF THE BLACK AND MEDITERRANEAN SEAS DURING THE HOLOCENE

Vertical movement of Earth crust can modify the shape of the eustatic sea level curves. A method allows calculation of the eustatic sea level course using the known local curves. We were able to divide a number of local curves of the Mediterranean Sea to the eustatic and tectonic components. The data about dynamics of the vertical crustal movements in 27 points of the Mediterranean coast and shelf during the Holocene were obtained. It was found that the velocities of raising and dipping are unstable over time and can reach value of 10 mm/year. Satellite measurements have recorded the velocities of vertical movements in the range of -10 to +20 mm/year for some parts of Black Sea coast. Such movements of the Earth's crust undoubtedly have a large impact on coastal processes and should be considered in designing coastal structures.

VERTICAL MOVEMENTS OF THE COAST AND SHELF OF THE BLACK AND MEDITERRANEAN SEAS DURING THE HOLOCENE

Vertical movement of Earth crust can modify the shape of the eustatic sea level curves. A method allows calculation of the eustatic sea level course using the known local curves. We were able to divide a number of local curves of the Mediterranean Sea to the eustatic and tectonic components. The data about dynamics of the vertical crustal movements in 27 points of the Mediterranean coast and shelf during the Holocene were obtained. It was found that the velocities of raising and dipping are unstable over time and can reach value of 10 mm/year. Satellite measurements have recorded the velocities of vertical movements in the range of -10 to +20 mm/year for some parts of Black Sea coast. Such movements of the Earth's crust undoubtedly have a large impact on coastal processes and should be considered in designing coastal structures.