We investigated the Late Pleistocene-Holocene crustal vertical movements off the coast of Marzamemi village in SE Sicily, Italy. By using a Synchronous Correlation Approach (SCA), we analysed ...terraced landforms that characterize a submerged sector within one of Southern Italy's most seismically active regions. In this area, the emerging portion of the NE-SW oriented bulge of the African foreland structurally shapes the coastal and marine regions off Marzamemi village.
Based on a newly created 17 km2 high-resolution bathymetric map generated from a Multibeam Echosounder (MBES) survey conducted in June 2021, we identified and examined four main paleo-shorelines identifying four submerged terraces. Terraced landforms play a crucial role in reconstructing Quaternary glacial and interglacial stages, offering insights into associated sea level fluctuations. Through the application of the SCA, our goal is to refine the chronology of these recently mapped and submerged marine terraces off the Marzamemi village, thereby contributing to the calculation of associated rates of crustal vertical movements. We demonstrate that these rates persist constantly throughout the Late Pleistocene-Holocene epoch, suggesting overall tectonic stability, with a slight and likely local fault-related subsidence. We explore a few chronology scenarios, raising questions about whether these submerged marine terraces are indeed recording the Late Pleistocene-Holocene limit or not. This research contributes to a better understanding of the geological dynamics in this region and sheds light on the potential factors influencing coastal landscape development over time.
•Geomorphological evolution of submerged paleoshorelines mapped in the Marzamemi offshore (SE Sicily) by GIS analysis is reconstructed•New ages estimation for undated submerged paleoshorelines are provided•New rates of crustal vertical movements in the Marzamemi offshore (SE Sicily) are estimated•Future works on the faulting activity affecting SE Sicily over the last 80 ka is stressed
Vertical land motions are a key element in understanding how sea levels have changed over the past century and how future sea levels may impact coastal areas. Ideally, to be useful in long‐term sea ...level studies, vertical land motion should be determined with standard errors that are 1 order of magnitude lower than the contemporary climate signals of 1 to 3 mm/yr observed on average in sea level records, either using tide gauges or satellites. This metrological requirement constitutes a challenge in geodesy. Here we review the most successful instrumental methods that have been used to determine vertical displacements at the Earth's surface, so that the objectives of understanding and anticipating sea levels can be addressed adequately in terms of accuracy. In this respect, the required level of uncertainty is examined in two case studies (global and local). A special focus is given to the use of the Global Positioning System (GPS) and to the combination of satellite radar altimetry with tide gauge data. We update previous data analyses and assess the quality of global satellite altimetry products available to the users for coastal applications. Despite recent advances, a near‐plateau level of accuracy has been reached. The major limitation is the realization of the terrestrial reference frame, whose physical parameters, the origin and the scale factor, are beyond the scope of a unique technique such as the GPS. Additional practical but nonetheless important issues are associated with the installation of GPS antennas, such as ensuring that there is no unknown differential vertical motion with the tide gauge.
Key Points
Vertical land motion: a key element to understanding sea level change along the coasts
Updated results on vertical land motion from the primary space geodetic methods
Discussion on the predominance of subsidence or uplift along the world coasts
NGA-West2 research project Bozorgnia, Yousef; Abrahamson, Norman A; Al Atik, Linda ...
Earthquake spectra,
08/2014, Volume:
30, Issue:
3
Journal Article
Peer reviewed
The NGA-West2 project is a large multidisciplinary, multi-year research program on the Next Generation Attenuation (NGA) models for shallow crustal earthquakes in active tectonic regions. The ...research project has been coordinated by the Pacific Earthquake Engineering Research Center (PEER), with extensive technical interactions among many individuals and organizations. NGA-West2 addresses several key issues in ground-motion seismic hazard, including updating the NGA database for a magnitude range of 3.0-7.9; updating NGA ground-motion prediction equations (GMPEs) for the "average" horizontal component; scaling response spectra for damping values other than 5%; quantifying the effects of directivity and directionality for horizontal ground motion; resolving discrepancies between the NGA and the National Earthquake Hazards Reduction Program (NEHRP) site amplification factors; analysis of epistemic uncertainty for NGA GMPEs; and developing GMPEs for vertical ground motion. This paper presents an overview of the NGA-West2 research program and its subprojects.
To examine the habitat usage of adult Pacific bluefin tuna (PBF), electronic tagging was conducted in the Sea of Japan during May and June of 2012-2017. Archival tags were internally implanted and ...pop-up satellite archival transmitting tags were deployed; data on the horizontal movements and diving behaviours of 36 individual PBF were successfully retrieved. In the summer spawning season, the tagged PBF were concentrated near Sado Island and Oki Island in the Sea of Japan, and they were distributed widely to the southwest (near Tsushima Island) or northeast (near the Tsugaru Strait) in the autumn and winter. We obtained the first long-term tracking record (246 d) for adult PBF, and this individual exhibited residency in a known spawning region during the spawning season in the proximity of warm-core eddy features. This fish spent most of the daytime below the thermocline between 30 and 150 m depths where the surface ambient temperature was 26.0 ± 1.5°C, but at night it ventured into the warm surface layer. Its whole-body heat transfer coefficient increased when it experienced warm waters (≥24°C), which we suggest is a physiological response to avoid overheating. The mean peritoneal cavity temperature was only 1.8°C higher than the ambient temperature, compared with 6.9°C higher during the cooler autumn-winter period. Our hypothesis is that the warm surface temperatures found in the spawning grounds induce a physiology-reproduction trade-off in adult PBF, which must behaviourally and physiologically thermoregulate their body temperature to gain spatial and temporal access to oceanographic conditions that may promote larval survivorship and growth.
GPS is accurately recording vertical motion of Earth's surface in elastic response to seasonal changes in surface water storage in California. California's mountains subside up to 12 mm in the fall ...and winter due to the load of snow and rain and then rise an identical amount in the spring and summer when the snow melts, the rain runs off, and soil moisture evaporates. We invert the GPS observations of seasonal vertical motions to infer changes in equivalent water thickness. GPS resolves the distribution of change in total water across California's physiographic provinces at a resolution of 50 km, compared to 200 km resolution from the Gravity Recovery and Climate Experiment. The seasonal surface water thickness change is 0.6 m in the Sierra Nevada, Klamath, and southern Cascade Mountains and decreases sharply to about 0.1 m east into the Great Basin and west toward the Pacific coast. GPS provides an independent inference of change in total surface water, indicating water storage to be on average 50% larger than in the NLDAS‐Noah hydrology model, likely due to larger changes in snow and reservoir water than in the model.
Key Points
GPS is used to determine changes in the storage of water and snow in California
GPS is used to distinguish between hydrological models
We provide a new analysis of glacial isostatic adjustment (GIA) with the goal of assembling the model uncertainty statistics required for rigorously extracting trends in surface mass from the Gravity ...Recovery and Climate Experiment (GRACE) mission. Such statistics are essential for deciphering sea level, ocean mass, and hydrological changes because the latter signals can be relatively small (≤2 mm/yr water height equivalent) over very large regions, such as major ocean basins and watersheds. With abundant new >7 year continuous measurements of vertical land motion (VLM) reported by Global Positioning System stations on bedrock and new relative sea level records, our new statistical evaluation of GIA uncertainties incorporates Bayesian methodologies. A unique aspect of the method is that both the ice history and 1‐D Earth structure vary through a total of 128,000 forward models. We find that best fit models poorly capture the statistical inferences needed to correctly invert for lower mantle viscosity and that GIA uncertainty exceeds the uncertainty ascribed to trends from 14 years of GRACE data in polar regions.
Key Points
We perform an inversion of GIA based on GPS and RSL data, varying mantle rheology and ice history
We derive formal uncertainty calculation of present‐day GIA, reflecting 128,000 forward models
The uncertainty is larger than previously reported and than GRACE RL05 inherent uncertainty estimation
We depict the relative sea-level rise scenarios for the year 2100 from four areas of the Italian peninsula. Our estimates are based on the Rahmstorf (2007) and IPCC-AR5 reports 2013 for the RCP-8.5 ...scenarios (www.ipcc.ch) of climate change, adjusted for the rates of vertical land movements (isostasy and tectonics). These latter are inferred from the elevation of MIS 5.5 deposits and from late Holocene sea-level indicators, matched against sea-level predictions for the same periods using the glacio-hydro-isostatic model of Lambeck et al. (2011). We focus on a variety of tectonic settings: the subsiding North Adriatic coast (including the Venice lagoon), two tectonically stable Sardinia coastal plains (Oristano and Cagliari), and the slightly uplifting Taranto coastal plain, in Apulia. Maps of flooding scenarios are shown on high-resolution Digital Terrain Models mostly based on Lidar data. The expected relative sea-level rise by 2100 will change dramatically the present-day morphology, potentially flooding up to about 5500 km2 of coastal plains at elevations close to present-day sea level.
The subsequent loss of land will impact the environment and local infrastructures, suggesting land planners and decision makers to take into account these scenarios for a cognizant coastal management. Our method developed for the Italian coast can be applied worldwide in other coastal areas expected to be affected by marine ingression due to global climate change.
Assessing the vertical land motion (VLM) at tide gauges (TG) is crucial to understanding global and regional mean sea-level changes (SLC) over the last century. However, estimating VLM with accuracy ...better than a few tenths of a millimeter per year is not a trivial undertaking and many factors, including the reference frame uncertainty, must be considered. Using a novel reconstruction approach and updated geodetic VLM corrections, we found the terrestrial reference frame and the estimated VLM uncertainty may contribute to the global SLC rate error by ±0.2 mmyr−1. In addition, a spurious global SLC acceleration may be introduced up to ±4.8×10−3 mmyr−2. Regional SLC rate and acceleration errors may be inflated by a factor 3 compared to the global. The difference of VLM from two independent Glacio-Isostatic Adjustment models introduces global SLC rate and acceleration biases at the level of ±0.1 mmyr−1 and 2.8×10−3 mmyr−2, increasing up to 0.5 mm yr−1 and 9×10−3 mmyr−2 for the regional SLC. Errors in VLM corrections need to be budgeted when considering past and future SLC scenarios.
•Large contribution of the reference frame realization on the SLC rate uncertainty.•Non-negligible contribution of uncertainty in the geodetic VLM estimates.•Differences in GIA VLM have the largest impact on regional SLC.•VLM errors can induce significant spurious SLC acceleration.•The impact of the relative VLM between GPS and TG is quantified globally.
Plate tectonics requires the formation of plate boundaries. Particularly important is the enigmatic initiation of subduction: the sliding of one plate below the other, and the primary driver of plate ...tectonics. A continuous, in situ record of subduction initiation was recovered by the International Ocean Discovery Program Expedition 352, which drilled a segment of the fore-arc of the Izu-Bonin-Mariana subduction system, revealing a distinct magmatic progression with a rapid timescale (approximately 1 million years). Here, using numerical models, we demonstrate that these observations cannot be produced by previously proposed horizontal external forcing. Instead a geodynamic evolution that is dominated by internal, vertical forces produces both the temporal and spatial distribution of magmatic products, and progresses to self-sustained subduction. Such a primarily internally driven initiation event is necessarily whole-plate scale and the rock sequence generated (also found along the Tethyan margin) may be considered as a smoking gun for this type of event.
Measurements of 189 continuous and 933 campaign-mode Global Positioning System (GPS) stations with 3–16 yr data spans over the Tibetan Plateau reveal contemporary three-dimensional (3-D) crustal ...deformation during 1999–2016. The Empirical Orthogonal Function method was used to characterize the spatial variations in the surface deformation with distinct seasonal oscillations at the GPS sites in five regions of the Tibetan Plateau. We find that these surface variations are highly correlated with the corresponding mass load signals observed by the Gravity Recovery and Climate Experiment (GRACE) mission. The improved GPS processing strategy used to determine the 3-D velocity field includes maximum likelihood estimation, removal of common mode errors from GPS time series using Principal Component Analysis (PCA), and power law plus white noise stochastic error modeling. We determined the rates of vertical crustal movement by removing GRACE-observed non-tectonic origin load deformation, 2002–2016. The corrected vertical crustal deformation shows that the Himalaya region is uplifting at an average rate of ∼1.7 mm yr−1, and that the northeastern Tibetan Plateau is uplifting at an average rate of ∼1.3 mm yr−1. In addition, the horizontal velocity relative to the stable Eurasian plate and its corresponding dilatation throughout the Tibetan Plateau suggest that tectonic shortening and crustal thickening is occurring at −90 to −80 nanostrain yr−1 in the southern Tibetan Plateau and −30 to −20 nanostrain yr−1 in the northeastern Tibetan Plateau, which could be related to the geologic shortening and elastic strain accumulation. The interior Tibetan Plateau exhibits crustal thinning and block movement along strike-slip faults. Eastward motion of the crust north of the Xianshuihe-Xiaojiang Fault system relative to crust to its south results in shear strain and reflects eastward escape of plastic crustal material in the southeastern Tibetan Plateau.
•Spatial surface seasonal oscillations throughout Tibetan Plateau (TP) are derived.•A 3-D crustal deformation field in TP is established using GPS and GRACE data.•The strain patterns of TP are derived by combining GPS horizontal velocity field.•This study reveals the crust shortening and vertical tectonic deformation of TP.
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