Coseismic Deformation Of The 2001 El Salvador And 2002 Denali Fault Earthquakes From Gps Geodetic Measurements

Thesis (Ph.D.) University of Alaska Fairbanks, 2005GPS geodetic measurements are used to study two major earthquakes, the 2001 MW 7.7 El Salvador and 2002 MW 7.9 Denali Fault earthquakes. The 2001 MW 7.7 earthquake was a normal fault event in the subducting Cocos plate offshore El Salvador. Coseismic displacements of up to 15 mm were measured at permanent GPS stations in Central America. The GPS data were used to constrain the location of and slip on the normal fault. One month later a MW 6.6 strike-slip earthquake occurred in the overriding Caribbean plate. Coulomb stress changes estimated from the M W 7.7 earthquake suggest that it triggered the MW 6.6 earthquake. Coseismic displacement from the MW 6.6 earthquake, about 40 mm at a GPS station in El Salvador, indicates that the earthquake triggered additional slip on a fault close to the GPS station. The MW 6.6 earthquake further changed the stress field in the overriding Caribbean plate, with triggered seismic activity occurring west and possibly also to the east of the rupture in the days to months following the earthquake. The MW 7.9 Denali Fault earthquake ruptured three faults in the interior of Alaska. It initiated with a thrust motion on the Susitna Glacier fault but then ruptured the Denali and Totschunda faults with predominantly right-lateral strike-slip motion unilaterally from west to east. GPS data measured in the two weeks following the earthquake suggest a complex coseismic rupture along the faults with two main regions of moment release along the Denali fault. A large amount of additional data were collected in the year following the earthquake which greatly improved the resolution on the fault, revealing more details of the slip distribution. We estimate a total moment release of 6.81 x 1020 Nm in the earthquake with a M W 7.2 thrust subevent on Susitna Glacier fault. The slip on the Denali fault is highly variable, with 4 main pulses of moment release. The largest moment pulse corresponds to a MW 7.5 subevent, about 40 km west of the Denali-Totschunda fault junction. We estimate relatively low and shallow slip on the Totschunda fault

Glacio-isostatic deformation around the Vatnajokull ice cap, Iceland, induced by recent climate warming: GPS observations and finite element modeling

Glaciers in Iceland began retreating around 1890, and since then the Vatnajökull ice cap has lost over 400 km3 of ice. The associated unloading of the crust induces a glacio‐isostatic response. From 1996 to 2004 a GPS network was measured around the southern edge of Vatnajökull. These measurements, together with more extended time series at several other GPS sites, indicate vertical velocities around the ice cap ranging from 9 to 25 mm/yr, and horizontal velocities in the range 3 to 4 mm/yr. The vertical velocities have been modeled using the finite element method (FEM) in order to constrain the viscosity structure beneath Vatnajökull. We use an axisymmetric Earth model with an elastic plate over a uniform viscoelastic half‐space. The observations are consistent with predictions based on an Earth model made up of an elastic plate with a thickness of 10–20 km and an underlying viscosity in the range 4–10 × 1018 Pa s. Knowledge of the Earth structure allows us to predict uplift around Vatnajökull in the next decades. According to our estimates of the rheological parameters, and assuming that ice thinning will continue at a similar rate during this century (about 4 km3/year), a minimum uplift of 2.5 meters between 2000 to 2100 is expected near the current ice cap edge. If the thinning rates were to double in response to global warming (about 8 km3/year), then the minimum uplift between 2000 to 2100 near the current ice cap edge is expected to be 3.7 meters

Commuting varieties of rr-tuples over Lie algebras

Let $G$ be a simple algebraic group defined over an algebraically closed field $k$ of characteristic $p$ and let \g be the Lie algebra of $G$. It is well known that for $p$ large enough the spectrum of the cohomology ring for the $r$-th Frobenius kernel of $G$ is homeomorphic to the commuting variety of $r$-tuples of elements in the nilpotent cone of \g [Suslin-Friedlander-Bendel, J. Amer. Math. Soc, \textbf{10} (1997), 693--728]. In this paper, we study both geometric and algebraic properties including irreducibility, singularity, normality and Cohen-Macaulayness of the commuting varieties C_r(\mathfrak{gl}_2), C_r(\fraksl_2) and $C_r(\N)$ where $\N$ is the nilpotent cone of \fraksl_2. Our calculations lead us to state a conjecture on Cohen-Macaulayness for commuting varieties of $r$-tuples. Furthermore, in the case when \g=\fraksl_2, we obtain interesting results about commuting varieties when adding more restrictions into each tuple. In the case of \fraksl_3, we are able to verify the aforementioned properties for C_r(\fraku). Finally, applying our calculations on the commuting variety C_r(\overline{\calO_{\sub}}) where \overline{\calO_{\sub}} is the closure of the subregular orbit in \fraksl_3, we prove that the nilpotent commuting variety $C_r(\N)$ has singularities of codimension $\ge 2$.Comment: To appear in Journal of Pure and Applied Algebr

Deformation at Krafla and Bjarnarflag geothermal areas, Northern Volcanic Zone of Iceland, 1993-2015

The Krafla volcanic system has geothermal areas within the Krafla caldera and at Bjarnarflag in the Krafla fissure swarm, 9-km south of the Krafla caldera. Arrays of boreholes extract geothermal fluids for power plants in both areas. We collected and analyzed InSAR, GPS, and leveling data spanning 1993–2015 in order to investigate crustal deformation in these areas. The volcanic zone hosting the geothermal areas is also subject to large scale regional deformation processes, including plate spreading and deflation of the Krafla volcanic system. These deformation processes have to be taken into account in order to isolate the geothermal deformation signal. Plate spreading produces the largest horizontal displacements, but the regional deformation pattern also suggests readjustment of the Krafla system at depth after the 1975–1984 Krafla rifting episode. Observed deformation can be fit by an inflation source at about 20 km depth north of Krafla and a deflation source at similar depth directly below the Krafla caldera. Deflation signal along the fissure swarm can be reproduced by a 1-km wide sill at 4 km depth closing by 2–4 cm per year. These sources are considered to approximate the combined effects of vertical deformation associated with plate spreading and post-rifting response. Local deformation at the geothermal areas is well resolved in addition to these signals. InSAR shows that deformation at Bjarnarflag is elongated along the direction of the Krafla fissure swarm (∼4 km by ∼2 km) while it is circular at Krafla (∼5 km diameter). Rates of deflation at Krafla and Bjarnarflag geothermal areas have been relatively steady. Average volume decrease of about 6.6 ×10⁵ m³/yr for Krafla and 3.9 ×10⁵ m³/yr for Bjanarflag are found at sources located at ∼1.5 km depth, when interpreted by a spherical point source of pressure. This volume change represents about 8 ×10 −3 m³/ton of the mass of geothermal fluid extracted per year, indicating important renewal of the geothermal reservoir by water flow

Web-Based Motor Intervention to Increase Health-Related Physical Fitness in Children With Congenital Heart Disease: A Study Protocol

Objective: Exercise interventions are underutilized in children with congenital heart disease (CHD) especially when the primary outcome is not peak oxygen uptake. Most of the studies are restricted to a low sample size and proximity of the patients to the study centers. Now eHealth approaches bear a promising but also challenging opportunity to transmit such intervention programs to participants, and check progress and compliance from remote. This study will aim to improve health-related physical fitness (HRPF) with a 24 weeks web-based exercise intervention.Methods and Design: The current study is planned as a randomized control trial (RCT) with a crossover design and the aim to improve functional outcome measures. It also estimates adherence and feasibility in patients with CHD in this web-based exercise/motor intervention over 24 weeks. Primary outcome will be the improvement of HRPF. Secondary outcomes are, functional and structural arterial stiffness measures and health-related quality of life. Thus, 70 children from 10 to 18 years with CHD of moderate and complex severity will be recruited and allocated randomly 1:1 in two study arms after baseline testing for their HRPF, arterial stiffness measures and health-related quality of life. For 24 weeks, participants in the intervention arm will receive three weekly exercise video clips of 20 min each. Every video clip comprises 20 child-oriented exercises which have to be executed for 30 s followed by a recovery period of 30 s. Each session will start with 3–4 warming-up exercises, followed by 10–12 strength and flexibility exercises, and ending with 3–4 min of cool down or stretching tasks. Continuous video clips will be streamed from a web-based e-Learning platform. The participant simply has to imitate the execution and follow some short advices. After each session, a brief online survey will be conducted to assess perceived exertion and feasibility.Discussion: The study will help to determine the efficacy and applicability of a web-based exercise intervention in children with CHD in regard to functional outcome measures. In addition, it will outline the effectiveness of remote monitoring, which provides a cost effective approach to reach patients with CHD that are low in prevalence and often do not live in close proximity to their tertiary center.Trial Registration:https://ClinicalTrials.gov Identifier: NCT03488797

Kinematic behavior of southern Alaska constrained by westward decreasing postglacial slip rates on the Denali Fault, Alaska

Long-term slip rates for the Denali Fault in southern Alaska are derived using ^(10)Be cosmogenic radionuclide (CRN) dating of offset glacial moraines at two sites. Correction of ^(10)Be CRN model ages for the effect of snow shielding uses historical, regional snow cover data scaled to the site altitudes. To integrate the time variation of snow cover, we included the relative changes in effective wetness over the last 11 ka, derived from lake-level records and δ^(18)O variations from Alaskan lakes. The moraine CRN model ages are normally distributed around an average of 12.1 ± 1.0 ka (n = 22, ± 1σ). The slip rate decreases westward from ~13 mm/a at 144°49′W to about 7 mm/a at 149°26′W. The data are consistent with a kinematic model in which southern Alaska translates northwestward at a rate of ~14 mm/a relative to a stable northern Alaska with no rotation. This suggests progressive slip partitioning between the Denali Fault and the active fold and thrust belt at the northern front of the Alaska range, with convergence rates increasing westward from ~4 mm/a to 11 mm/a between ~149°W and 145°W. As the two moraines sampled for this study were emplaced synchronously, our suggestion of a westward decrease in the slip rate of the Denali Fault relies largely upon the measured offsets at both sites, regardless of any potential systematic uncertainty in the CRN model ages

Förlusten av ett barn : en litteraturstudie om föräldrars upplevelse under sorgarbetet

Att förlora sitt barn är den svåraste förlust en förälder kan uppleva i livet. Sorgen blir påtaglig och livet raseras på ett ögonblick. Syftet med studien var att beskriva föräldrarnas upplevelse under sorgarbetet vid förlusten av ett barn. Metoden som användes var en litteraturstudie med kvalitativ innehållsanalys. Resultatet sammanställdes utifrån åtta vetenskapliga artiklar som svarade på studiens syfte. I resultatet framkom att föräldrarna upplever en djup och smärtsam sorg efter förlusten av sitt barn. Sorgarbetet tar lång tid för föräldrarna, deras sorgreaktioner kan variera mycket och sorgen är mycket individuell. Det är viktigt för föräldrarna att familj och vänner vågar vara nära genom sorgarbetet och föräldrarna upplever ett stort behov av att tala om sitt förlorade barn. Föräldrars relation och hälsa kan påverkas temporärt eller permanent under sorgarbetet eller förbli oförändrad. Trots den svåra sorgen lärde sig de flesta föräldrarna att uppskatta och njuta av livet igen. Studien riktas främst till sjuksköterskor men kan även tillämpas av andra som kommer i kontakt med sörjande föräldrar

Förlusten av ett barn : en litteraturstudie om föräldrars upplevelse under sorgarbetet

Att förlora sitt barn är den svåraste förlust en förälder kan uppleva i livet. Sorgen blir påtaglig och livet raseras på ett ögonblick. Syftet med studien var att beskriva föräldrarnas upplevelse under sorgarbetet vid förlusten av ett barn. Metoden som användes var en litteraturstudie med kvalitativ innehållsanalys. Resultatet sammanställdes utifrån åtta vetenskapliga artiklar som svarade på studiens syfte. I resultatet framkom att föräldrarna upplever en djup och smärtsam sorg efter förlusten av sitt barn. Sorgarbetet tar lång tid för föräldrarna, deras sorgreaktioner kan variera mycket och sorgen är mycket individuell. Det är viktigt för föräldrarna att familj och vänner vågar vara nära genom sorgarbetet och föräldrarna upplever ett stort behov av att tala om sitt förlorade barn. Föräldrars relation och hälsa kan påverkas temporärt eller permanent under sorgarbetet eller förbli oförändrad. Trots den svåra sorgen lärde sig de flesta föräldrarna att uppskatta och njuta av livet igen. Studien riktas främst till sjuksköterskor men kan även tillämpas av andra som kommer i kontakt med sörjande föräldrar