Geodetic measurement of tectonic deformation in central California

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.Includes bibliographical references (p. 203-222).by Kurt Lewis Feigl.Ph.D

Triggered fault slip on June 17, 2000 on the Reykjanes Peninsula, SW-Iceland captured by radar interferometry

Dynamically triggered seismicity followed shortly after a M-s 6.6 earthquake in Iceland on June 17, 2000. Smaller earthquakes occurred on the Reykjanes Peninsula up to 100 km from the mainshock rupture. Using interferometric analysis of Synthetic Aperture Radar images (InSAR), we measure crustal deformation associated with three triggered deformation events. The largest of these occurred at Lake Kleifarvatn, 85 km west of the mainshock epicenter. Modeling of the InSAR data reveals strikeslip on a north-striking fault, with a geodetic moment of 6.2 x 10(17) Nm, equivalent to magnitude M-w 5.8 earthquake. A seismological estimate of the moment is not yet available, because the seismic signature of this event is partly hidden by the mainshock waveform. The paucity of aftershocks on the triggered rupture plane suggests some aseismic slip there, compatible with a thin seismogenic crust, high heat-flow, hydrothermal alteration and the presence of fluids in the area

Measuring long-term and constant rate ground motion by satellite radar interferometry: Avcılar case

Radar interferometrisi (InSAR), birbirine çok yakın görüntüleme geometrileriyle elde edilmiş iki farklı radar görüntüsü arasında oluşan faz farkını hesaplayan bir tekniktir. Faz farkı, uydu platformunda bulunan radar ile yeryüzünde görüntülenen nokta arasındaki uzaklığa karşılık gelmektedir. Günümüzde InSAR, yüzey deformasyonunun ölçülmesinde etkili bir teknik olarak kabul edilmektedir. Diğer yandan, tekniğin uygulanabilirliği radar sinyalinin korelasyonu ve atmosferik etkilerle sınırlıdır. Bu çalışmada, uzun zamanda oluşan yüzey deformasyonunu ölçmek için, ERS-1 ve ERS-2 uydularından elde edilen radar görüntüleri kullanılarak bir strateji geliştirilmiştir. Yöntem, ham SAR verilerinin seçimi, SAR veri-işleme ve post-veri-işleme adımlarını içermektedir.  Çalışmada, Avrupa Uzay Ajansı’nın (ESA) 1992-2002 yılları arasında ERS uydularıyla elde ettiği radar görüntüleri kullanılmıştır. Radar görüntü çiftleri, çeşitli veri-seçimi kriterleriyle belirlenmiştir. Radar görüntülerindeki faz ölçmelerinin yoğunluğu, “permanent saçıcılar” (PS) tekniği kullanılarak azaltılmıştır. 1992 ve 1999 yılları arasındaki maksimum yerdeğiştirme hızı, Avcılar’ın batısında bir noktada -7 mm/yıl olarak belirlenmiştir. Birinci yazarın diğer çalışmalarında detaylı olarak belirtildiği üzere; Avcılar’da uzun zamandır sabit hızda oluşan yer hareketleri, bölgede var olduğu bilinen toprak kaymalarıyla ilişkilidir. Yerdeğiştime hızlarının dağılımı,  yağışlı mevsimde süreksiz olarak oluşan toprak kaymalarının, kayma ve oturma şeklinde bütün sene boyunca sürdüğünü göstermektedir. Anahtar Kelimeler: Uydu radar interferometrisi, yüzey deformasyonu, jeodezi, uzaktan algılama. Radar interferometry (InSAR) is a technique that calculates the phase difference between two radar images acquired by slightly different viewing geometries (Massonnet and Feigl, 1998; Hanssen, 2001; Madsen and Zebker, 1998; Burgmann et al., 2000; Rosen et al., 2000; Gens and van Genderen, 1996). The resultant interference pattern is called an “interferogram”. If certain conditions are met, the phase differences form spatially coherent fringes. Each fringe represents a difference of one cycle of the two-way travel time between the radar aboard the satellite and the target on the ground. Interpreted in units of distance, each fringe represents half the radar wavelength in change of distance, or 28 mm for C-band radars aboard ERS and ENVISAT satellites. While conventional InSAR has been proven to be a very effective technique to measure ground motion, its applicability is limited mainly by radar signal correlation and atmospheric effects. Therefore, to measure slow ground motion occurring over long times requires a challenging effort if conventional InSAR techniques are to be used. If one of the scatterers contributing to the pixel is much more stable than the others, then its contribution to the phase and amplitude measurements will dominate those from the other scatterers. If we can identify these pixels represented by a single strong scattarer, then we can simplify the process of interpreting the interferograms. These persistent scatterers (hence called “PS pixels”) are more reliable because they are less susceptible to all processes causing decorrelation. Accordingly, they have less noise then other pixels. Once the data set has been reduced in size by several orders of magnitude by selecting only the reliable PS pixels in the interferograms, the subsequent interpretation and analysis involving unwrapping and modeling are considerably simpler. Several approaches have been proposed for identifying PS pixels since 2000 (e.g. Hanssen and Usai, 1997; Ferretti et al., 2000, 2001; Colesanti et al., 2003a, 2003b; Lyons and Sandwell, 2003; Hooper et al., 2004; Hooper, 2006). In this study, we establish a radar data selection and processing flow for measuring slow ground motion occuring over long times. We combine different methodologies in raw radar data processing and post-processing. All the steps presented in the study are repeatable and applicable to ERS SAR data for measuring slow motion deformation. We use the entire radar data set of ERS-1 and ERS-2 satellites  for the data frame titled as Track 336 and Frame 2783 (T336/F2783). This frame covers all Istanbul metropolitan area and contains 48 epochs between 1992 and 2000. For the deformation analysis, we choose a data frame of 4x5 km2 that covers the Avcılar vicinity of Istanbul. We process the raw SAR data using DIAPASON software (Differential Interferometric Automated Process Applied to Survey of Nature) (version 4.1) developed at the French Space Agency (Massonnet et al., 1994; CNES, 1998; CNES, 2003a). The PS pixels persistent to phase decorrelation are selected through their “amplitude dispersion index” DA, as defined by Ferretti et al. (2000, 2001) and multi-coherence γ, as described by Colesanti (2003). We use “General Inversion for Phase Technique” (GIPhT) developed by Feigl and Thurber (2009) for modeling interferograms. GIPhT defines a misfit cost C between the model and the phase observations. By minimizing the cost C, this approach can solve simultaneously for both linear and non-linear parameters. Analysis of 14 image epochs between 1992 and 1999 has revealed downward ground motion around the Avcılar district of Istanbul. We have analyzed a set of 24 interferometric pairs with PS coverage of 7 PS/km2. The PS coverage corresponds to 1% of the image pixels. Three subsidence sources with a constant subsiding rate have been modeled by using a simple 4-parameter Mogi source (easting, northing, volume, depth). Also, a tropospheric parameter (vertical gradient) for each epoch has been included to the parameter set. The final model fits the phase data significantly better than the prior model based on F-test with 95 % confidence. We find a maximum displacement rate of -7 mm/yr at a point located at latitude 40.98ºN and longitude 28.71ºE. Akarvardar et al. (2007) and Akarvardar (2007) suggest that most of the downward ground motion occurs in the landslide areas. It seems likely that the soils once displaced after landslides have continued to slide and settle down with a constant rate between 1992 and 1999. Keywords: Satellite radar interferometry, ground motion, geodesy, remote sensing

Twenty-five years of geodetic measurements along the Tadjoura-Asal rift system, Djibouti, East Africa

International audienceSince most of Tadjoura-Asal rift system sits on dry land in the Afar depression near the triple junction between the Arabia, Somalia, and Nubia plates, it is an ideal natural laboratory for studying rifting processes. We analyze these processes in light of a time series of geodetic measurements from 1978 through. A network of about 30 GPS sites covers the Republic of Djibouti. Additional points were also measured in Yemen and Ethiopia. Stations lying in the Danakil block have almost the same velocity as Arabian plate, indicating that opening near the southern tip of the Red Sea is almost totally accommodated in the Afar depression. Inside Djibouti, the Asal-Ghoubbet rift system accommodates 16 ± 1 mm/yr of opening perpendicular to the rift axis and exhibits a pronounced asymmetry with essentially null deformation on its southwestern side and significant deformation on its northeastern side. This rate, slightly higher than the large-scale Arabia-Somalia motion (13 ± 1 mm/yr), suggests transient variations associated with relaxation processes following the Asal-Ghoubbet seismovolcanic sequence of 1978. Inside the rift, the deformation pattern exhibits a clear two-dimensional pattern. Along the rift axis, the rate decreases to the northwest, suggesting propagation in the same direction. Perpendicular to the rift axis, the focus of the opening is clearly shifted to the northeast, relative to the topographic rift axis, in the ''Petit Rift,'' a rift-in-rift structure, containing most of the active faults and the seismicity. Vertical motions, measured by differential leveling, show the same asymmetric pattern with a bulge of the northeastern shoulder. Although the inner floor of the rift is subsiding with respect to the shoulders, all sites within the rift system show uplift at rates varying from 0 to 10 mm/yr with respect to a far-field reference outside the rift

Active tectonics of the western Mediterranean: Geodetic evidence for roll back of a delaminated subcontinental lithospheric slab beneath the Rif Mountains, Morocco

Copyright 2006, Geological Society of America. See also: http://www.geosociety.org; http://atlas.geo.cornell.edu/morocco/publications/fadil2006.htmSurface deformation in Morocco derived from five years of GPS survey observations of a 22-station network, four continuously recording GPS stations, and four IGS stations in Iberia indicate roughly southward motion (~3 mm/yr) of the Rif Mountains, Morocco relative to stable Africa. Motion of the Rif is approximately normal to the direction of Africa-Eurasia relative motion, which is predominantly strike slip, and results in shortening of the Rif and subsequent crustal extension of the adjacent Alboran Sea region. The sense, and the N-S asymmetry of the observed deformation (i.e., no evidence for north-directed shortening in the Betic Mountains north of the Alboran Sea) cannot be easily explained in terms of crustal plate interactions suggesting that dynamic processes below the crust are driving the recent geologic evolution of the western Mediterranean. The model that best fits the observations involves delamination and southward roll back of the African lithospheric mantle under the Alboran and Rif domains

Non-standard neutrino interactions in IceCube

Non-standard neutrino interactions (NSI) may arise in various types of new physics. Their existence would change the potential that atmospheric neutrinos encounter when traversing Earth matter and hence alter their oscillation behavior. This imprint on coherent neutrino forward scattering can be probed using high-statistics neutrino experiments such as IceCube and its low-energy extension, DeepCore. Both provide extensive data samples that include all neutrino flavors, with oscillation baselines between tens of kilometers and the diameter of the Earth. DeepCore event energies reach from a few GeV up to the order of 100 GeV - which marks the lower threshold for higher energy IceCube atmospheric samples, ranging up to 10 TeV. In DeepCore data, the large sample size and energy range allow us to consider not only flavor-violating and flavor-nonuniversal NSI in the μ−τ sector, but also those involving electron flavor. The effective parameterization used in our analyses is independent of the underlying model and the new physics mass scale. In this way, competitive limits on several NSI parameters have been set in the past. The 8 years of data available now result in significantly improved sensitivities. This improvement stems not only from the increase in statistics but also from substantial improvement in the treatment of systematic uncertainties, background rejection and event reconstruction

Anatomy of the sign-problem in heavy-dense QCD

QCD at finite densities of heavy quarks is investigated using the density-of-states method. The phase factor expectation value of the quark determinant is calculated to unprecedented precision as a function of the chemical potential. Results are validated using those from a reweighting approach where the latter can produce a significant signalto-noise ratio. We confirm the particle–hole symmetry at low temperatures, find a strong sign problem at intermediate values of the chemical potential, and an inverse Silver Blaze feature for chemical potentials close to the onset value: here, the phase-quenched theory underestimates the density of the full theory

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements