The sensitivity of GNSS measurements in Fennoscandia to distinct three-dimensional upper-mantle structures

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Glacial Isostatic Adjustment as a key to understand the neotectonics of northern Central Europe

Theme: Media advisory 2 - Meeting programme online, provisional press conference topicsNorthern Central Europe is generally regarded as aseismic, however, several historic earthquakes with intensities of up to VII occurred in this region during the last 1200 years (Leydecker, 2009). In a pilot study we analysed the Osning Thrust, which is a one of the major Mesozoic fault zones in northern Central Europe. Several soft-sediment ...published_or_final_versio

Optimal locations of sea-level indicators in glacial isostatic adjustment investigations

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Intraplate seismicity in northern Central Europe is induced by the last glaciation

There is growing evidence that climate-induced melting of large ice sheets has been able to trigger fault reactivation and earthquakes around the migrating ice limit. Even today, the stress due to glacial isostatic adjustment can continue to induce seismicity within the once glaciated region. Northern Central Europe lies outside the former ice margin and is regarded as a low-seismicity area. However, several historic earthquakes with intensities of up to VII occurred in this region during the past 1200 years. Here we show with numerical simulations that the seismicity can potentially be explained by the decay of the Scandinavian ice sheet after the Weichselian glaciation. Combination of historic earthquake epicenters with fault maps relates historic seismicity to major reverse faults of Late Cretaceous age. Mesozoic normal faults remained inactive in historic times. We suggest that many faults in northern Central Europe are active during postglacial times. This is a novelty that sheds new light on the distribution of postglacial faulting and seismicity. In addition, we present the first consistent model that can explain both the occurrence of deglaciation seismicity and the historic earthquakes in northern Central Europe.postprin

Reply to comment by Hampel et al. on “Stress and fault parameters affecting fault slip magnitude and activation time during a glacial cycle”

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Stress and fault parameters affecting fault slip magnitude and activation time during a glacial cycle

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Groundwater storage changes in the Tibetan Plateau and adjacent areas revealed from GRACE satellite gravity data

Understanding groundwater storage (GWS) changes is vital to the utilization and control of water resources in the Tibetan Plateau. However, well level observations are rare in this big area, and reliable hydrology models including GWS are not available. We use hydro-geodesy to quantitate GWS changes in the Tibetan Plateau and surroundings from 2003 to 2009 using a combined analysis of satellite gravity and satellite altimetry data, hydrology models as well as a model of glacial isostatic adjustment (GIA). Release-5 GRACE gravity data are jointly used in a mascon fitting method to estimate the terrestrial water storage (TWS) changes during the period, from which the hydrology contributions and the GIA effects are effectively deducted to give the estimates of GWS changes for 12 selected regions of interest. The hydrology contributions are carefully calculated from glaciers and lakes by ICESat-1 satellite altimetry data, permafrost degradation by an Active-Layer Depth (ALD) model, soil moisture and snow water equivalent by multiple hydrology models, and the GIA effects are calculated with the new ICE-6G_C (VM5a) model. Taking into account the measurement errors and the variability of the models, the uncertainties are rigorously estimated for the TWS changes, the hydrology contributions (including GWS changes) and the GIA effect. For the first time, we show explicitly separated GWS changes in the Tibetan Plateau and adjacent areas except for those to the south of the Himalayas. We find increasing trend rates for eight basins: +2.46 ±2.24Gt/yrfor the Jinsha River basin, +1.77 ±2.09Gt/yrfor the Nujiang-Lancangjiang Rivers Source Region, +1.86 ±1.69Gt/yrfor the Yangtze River Source Region, +1.14 ±1.39Gt/yrfor the Yellow River Source Region, +1.52 ±0.95Gt/yrfor the Qaidam basin, +1.66 ±1.52Gt/yrfor the central Qiangtang Nature Reserve, +5.37 ±2.17Gt/yrfor the Upper Indus basin and +2.77 ±0.99Gt/yrfor the Aksu River basin. All these increasing trends are most likely caused by increased runoff recharges from melt water and/or precipitation in the surroundings. We also find that the administrative actions such as the Chinese Ecological Protection and Construction Project help to store more groundwater in the Three Rivers Source Region, and suggest that seepages from the Endorheic basin to the west of it are a possible source for GWS increase in this region. In addition, our estimates for GWS changes basically confirm previous results along Afghanistan, Pakistan, north India and Bangladesh, and clearly reflect the excessive use of groundwater. Our results will benefit the water resource management in the study area, and are of particular significance for the ecological restoration in the Tibetan Plateau.published_or_final_versio

A GPS velocity field for Fennoscandia and a consistent comparison to glacial isostatic adjustment models

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Influences of crustal thickening in the Tibetan Plateau on loading modeling and inversion associated with water storage variation

We use the average crustal structure of the CRUST1.0 model for the Tibetan Plateau to establish a realistic earth model termed as TC1P, and data from the Global Land Data Assimilation System (GLDAS) hydrology model and Gravity Recovery and Climate Experiment (GRACE) data, to generate the hydrology signals assumed in this study. Modeling of surface radial displacements and gravity variation is performed using both TC1P and the global Preliminary Reference Earth Model (PREM). Furthermore, inversions of the hydrology signals based on simulated Global Positioning System (GPS) and GRACE data are performed using PREM. Results show that crust in TC1P is harder and softer than that in PREM above and below a depth of 15 km, respectively, causing larger differences in the computed load Love numbers and loading Green's functions. When annual hydrology signals are assumed, the differences of the radial displacements are found to be as large as approximately 0.6 mm for the truncated degree of 180; while for hydrology-trend signals the differences are very small. When annual hydrology signals and the trends are assumed, the differences in the surface gravity variation are very small. It is considered that TC1P can be used to efficiently remove the hydrological effects on the monitoring of crustal movement. It was also found that when PREM is used inappropriately, the inversion of the hydrology signals from simulated annual GPS signals can only recover approximately 88.0% of the annual hydrology signals for the truncated degree of 180, and the inversion of hydrology signals from the simulated trend GPS signals can recover approximately 92.5% for the truncated degree of 90. However, when using the simulated GRACE data, it is possible to recover almost 100%. Therefore, in future, the TC1P model can be used in the inversions of hydrology signals based on GPS network data. PREM is also valid for use with inversions of hydrology signals from GRACE data at resolutions of approximately 220 km and larger.published_or_final_versio

Water storage changes in North America retrieved from GRACE gravity and GPS data

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