ALBERT

Description: The ability of any satellite gravity mission concept to monitor mass transport processes in the Earth system is typically tested well ahead of its implementation by means of various simulation studies. Those studies often extend from the simulation of realistic orbits and instrumental data all the way down to the retrieval of global gravity field solution time-series. Basic requirement for all these simulations are realistic representations of the spatio-temporal mass variability in the different sub-systems of the Earth, as a source model for the orbit computations. For such simulations, a suitable source model is required to represent (i) high-frequency (i.e., subdaily to weekly) mass variability in the atmosphere and oceans, in order to realistically include the effects of temporal aliasing due to non-tidal high-frequency mass variability into the retrieved gravity fields. In parallel, (ii) low-frequency (i.e., monthly to interannual) variability needs to be modelled with realistic amplitudes, particularly at small spatial scales, in order to assess to what extent a new mission concept might provide further insight into physical processes currently not observable. The new source model documented here attempts to fulfil both requirements: Based on ECMWF’s recent atmospheric reanalysis ERA-Interim and corresponding simulations from numerical models of the other Earth system components, it offers spherical harmonic coefficients of the time-variable global gravity field due to mass variability in atmosphere, oceans, the terrestrial hydrosphere including the ice-sheets and glaciers, as well as the solid Earth. Simulated features range from sub-daily to multiyear periods with a spatial resolution of spherical harmonics degree and order 180 over a period of 12 years. In addition to the source model, a de-aliasing model for atmospheric and oceanic high-frequency variability with augmented systematic and random noise is required for a realistic simulation of the gravity field retrieval process, whose necessary error characteristics are discussed. The documentation of the updated ESA Earth System Model (updated ESM) for gravity mission simulation studies is organized as follows: The characteristics of the updated ESM along with some basic validation is presented in Volume 1. A detailed comparison to the original ESA ESM (Gruber et al., 2011) is provided in Volume 2, while Volume 3 contains the description of a strategy to derive realistic errors for the de-aliasing model of high-frequency mass variability in atmosphere and ocean.

Description: The integrated plate boundary in Chile (IPOC) combines 15 broadband stations with strong-motion sensors, GPS, strain sensors and magneto-telluric stations. The Chilean subduction zone setting provides a high background rate of seismicity (crustal, intermediate depth, and plate interface) in a region with exceptionally low ambient noise, particularly at higher frequencies. We have deployed seismic mini-arrays in the vicinity of IPOC stations PB02 and PB07, and installed a third array to the east of these stations near the village of Quillagua, such that all three arrays form a triangle. Each array has 10 elements and an aperture in the km range. The study area lies just to the north of the northern boundary of the rupture area of the Tocopilla earthquake of 2007 Mw=7.7) and just above or slightly to the east of the downdip limit of plate interface seismicity. Installing the mini-arrays in the area of the existing IPOC has the following advantages: • Independent knowledge of background structure and seismicity from existing and ongoing studies. • Should any transients or other unusual signals be found in the array data, we can look for anomalous signals in geodetic and MT recordings, which will help to narrow down possible underlying mechanisms.

Description: This paper presents the first published 3D geomechanical modelling study of the CO2CRC Otway Project, located in the state of Victoria, Australia. The results of this work contribute to one of the main objectives of the CO2CRC, which is to demonstrate the feasibility of CO2 storage in a depleted gas reservoir. With this aim in mind, a one-way coupled flow and geomechanics model is presented, with the capability of predicting changes to the in situ stress field caused by changes in reservoir pressure owing to CO2 production and injection. A parametric study investigating the pore pressures required to reactivate key, reservoir-bounding faults has been conducted, and the results from the numerical simulation and analytical analysis are compared. The numerical simulation indicates that the critical pore fluid pressure to cause fault reactivation is 1.15 times the original pressure as opposed to 1.5 times for the comparable analytical model. Possible reasons for the differences between the numerical and analytical models can be ascribed to the higher degree of complexity incorporated in the numerical model. Heterogeneity in terms of lateral variations of hydrological and mechanical parameters, effect of topography, presence of faults and interaction between cells are considered to be the main sources for the different estimation of critical pore pressure. The numerical model, which incorporates this greater complexity, is able then to better describe the state of stress that acts in the subsurface compared with a simple 1D analytical model. Moreover, the reactivation pressures depend mainly on the state of stress described; therefore we suggest that numerical models be performed when possible.

Description: Bram, K.: Logging and testing in the superdeep borehole KTB-Oberpfalz HB: Concept and first results of the depth interval 0 - 6018 m. p. 3-21. Zoth, G.: Logging Center. p. 25-57. Bram, K., Kück, J.: Information on the Borehole KTB-Oberpfalz HB. p. 61-65. Draxler, J.: Logging Programme. p. 69-73. Draxler, J., Kück, J.: Logging Activity in the Borehole KTB-Oberpfalz HB. p. 77-83. Draxler, J.: Intermediate Logs. p. 87-93. Draxler, J.: Logging Operations at Casing Depth 6018.0 m (driller's depth). p. 97-175. Draxler, J.: New Tools. p. 179-183. Hirschmann, G., Kück, J.: Data Evaluation and Reports: KTB Hauptbohrung - relations between the borehole deviation and the geological structure. p. 187-189. Kück, J.: Data Evaluation and Reports: BGLQUICK and MUDQUICK quicklook data plots. p. 191-197. Sturmeit, K.-D.: Data Evaluation and Reports: SEL - A computer program to manage and present data of downhole measurements. p. 199-213. Zoth, G.: Data Evaluation and Reports: Temperature measurements during the 6000 m logging campaign in the KTB-Oberpfalz HB. p. 215-217. Bram, K., Gatto, H.: Data Evaluation and Reports: Determination of sonic velocities from KTB borehole acoustic logs. p. 219-235. Stoll, J.: Data Evaluation and Reports: A Mise-a-la-Masse experiment for detecting an electric network in cataclastic zones around the KTB-site. p. 237-250. Gatto, H.: Data Evaluation and Reports: Determination of elements through geochemical logging in crystalline rocks of the KTB-Oberpfalz HB. p. 251-264. Peching, R., Wohlenberg, J.: Data Evaluation and Reports: EFA-LOG - The upper 3 km of the KTB-Hauptbohrung. p. 265-280. Brudy, M., Fuchs, K., Zoback, M. D.: Data Evaluation and Reports: Stress Orientation Profile to 6 km Depth in the KTB Main Borehole. p. 281-300. Engeser, B., Huenges, E., Kessels, W., Kück, J., Wohlgemuth, L.: Data Evaluation and Reports: The 6000 m hydrofrac test in the KTB main borehole design, implementation and preliminary results. p. 301-336. Kessels, W., Kück, J.: Data Evaluation and Reports: Hydraulic communication in crystalline rocks between the two boreholes of the Continental Deep Drilling Programme in Germany. p. 337-365.