Present kinematics of the Tjörnes Fracture Zone, North Iceland, from campaign and continuous GPS measurements

The Tjörnes Fracture Zone (TFZ), North Iceland, is a 120 km transform offset of the Mid-Atlantic-Ridge that accommodates 18mmyr−1 plate motion on two parallel transform structures and connects the offshore Kolbeinsey Ridge in the north to the on-shore Northern Volcanic Zone (NVZ) in the south. This transform zone is offshore except for a part of the right-lateral strike-slip Húsavík-Flatey fault (HFF) system that lies close to the coastal town of Húsavík, inducing a significant seismic risk to its inhabitants. In our previous work we constrained the locking depth and slip-rate of the HFF using 4 yr of continuous GPS measurements and found that the accumulated slip-deficit on the fault is equivalent to a Mw6.8± 0.1 earthquake, assuming a complete stress release in the last major earthquakes in 1872 and a steady accumulation since then. In this paper we improve our previous analysis by adding 44 campaign GPS (EGPS) data points, which have been regularly observed since 1997. We extract the steady-state interseismic velocities within the TFZ by correcting the GPS data for volcanic inflation of Theistareykir—the westernmost volcano of the NVZ—using a model with a magma volume increase of 25× 106m3, constrained by InSAR time-series analysis results. The improved velocity field based on 58 GPS stations confirms the robustness of our previous model and allows to better constrain the free model parameters. For the HFF we find a slightly shallower locking depth of ∼6.2km and a slightly higher slip-rate of ∼6.8mmyr−1 that again result in the same seismic potential equivalent to a Mw6.8 earthquake. The much larger number of GPS velocities improves the statistically estimated model parameter uncertainties by a factor of two, when compared to our previous study, a result that we validate using Bayesian estimatio

Short-term variations of Icelandic ice cap mass inferred from cGPS coordinate time series

As the global climate changes, understanding short-term variations in water storage is increasingly important. Continuously operating Global Positioning System (cGPS) stations in Iceland record annual periodic motion—the elastic response to winter accumulation and spring melt seasons—with peak-to-peak vertical amplitudes over 20 mm for those sites in the Central Highlands. Here for the first time for Iceland, we demonstrate the utility of these cGPS-measured displacements for estimating seasonal and shorter-term ice cap mass changes. We calculate unit responses to each of the five largest ice caps in central Iceland at each of the 62 cGPS locations using an elastic half-space model and estimate ice mass variations from the cGPS time series using a simple least squares inversion scheme. We utilize all three components of motion, taking advantage of the seasonal motion recorded in the horizontal. We remove secular velocities and accelerations and explore the impact that seasonal motions due to atmospheric, hydrologic, and nontidal ocean loading have on our inversion results. Our results match available summer and winter mass balance measurements well, and we reproduce the seasonal stake-based observations of loading and melting within the 1 math formula confidence bounds of the inversion. We identify nonperiodic ice mass changes associated with interannual variability in precipitation and other processes such as increased melting due to reduced ice surface albedo or decreased melting due to ice cap insulation in response to tephra deposition following volcanic eruptions, processes that are not resolved with once or twice-yearly stake measurements

Evolution of deformation and stress changes during the caldera collapse and dyking at Bárdarbunga, 2014–2015: Implication for triggering of seismicity at nearby Tungnafellsjökull volcano

Stress transfer associated with an earthquake, which may result in the seismic triggering of aftershocks (earthquake–earthquake interactions) and/or increased volcanic activity (earthquake–volcano interactions), is a well-documented phenomenon. However limited studies have been undertaken concerning volcanic triggering of activity at neighbouring volcanoes (volcano–volcano interactions). Here we present new deformation and stress modelling results utilising a wealth of diverse geodetic observations acquired during the 2014–2015 unrest and eruption within the Bárdarbunga volcanic system. These comprise a combination of InSAR, GPS, LiDAR, radar profiling and optical satellite measurements. We find a strong correlation between the locations of increased seismicity at nearby Tungnafellsjökull volcano and regions of increased tensile and Coulomb stress changes. Our results suggest that stress transfer during this major event has resulted in earthquake triggering at the neighbouring Tungnafellsjökull volcano by unclamping faults within the associated fissure swarm. This work has immediate application to volcano monitoring; to distinguish the difference between stress transfer and new intrusive activity

Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow

Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption.We usemultiparameter geophysical and geochemical data to show that the 110-squarekilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, nearexponential decline of both collapse rate and the intensity of the 180-day-long eruption.</p

Viðhorf skjólstæðinga til þjónustu iðjuþjálfa

Í dag eru einstaklingar farnir að gera kröfur um að vera þátttakendur í þeirri heilbrigðisþjónustu sem þeim er veitt og vilja taka ábyrgð á henni. Iðjuþjálfar hafa reynt að koma til móts við þessar kröfur með því að veita skjólstæðingsmiðaða iðjuþjálfun en hún leggur áherslu á samvinnu, gagnkvæma virðingu og samábyrgð iðjuþjálfa og skjólstæðins. Heimildir sýna að skjólstæðingsmiðuð iðjuþjálfun eykur árangur í iðjuþjálfun og ánægju skjólstæðinga með þjónustu iðjuþjálfa. Aðaltilgangur verkefnisins var að kanna viðhorf skjólstæðinga í endurhæfingu til þjónustu iðjuþjálfa með því að fá upplýsingar um hvort þjónusta iðjuþjálfa hafi verið skjólstæðingsmiðuð, hversu ánægðir skjólstæðingar voru með þjónustuna og hvort hún hafi borið árangur og þá hvernig. Spurningalisti var sendur til þátttakenda til að afla upplýsinga í rannsókninni. Úrtakið var 38 einstaklingar sem notið höfðu þjónustu iðjuþjálfa á Landspítala háskólasjúkrahúsi (LSH) Grensási og svöruðu 22 (58%) einstaklingar spurningalistanum. Lýsandi megindleg rannsóknaraðferð var notuð og niðurstöður settar fram í texta og myndum. Niðurstöður sýndu að viðhorf skjólstæðinga í endurhæfingu til þjónustu iðjuþjálfa var almennt jákvætt þar sem flestir þátttakendur voru ánægðir með þjónustuna og töldu að hún hafði borið árangur. Einnig voru sjö lykilþættir skjólstæðingsmiðaðrar iðjuþjálfunar að mestu leyti hafðir að leiðarljósi í þjónustu iðjuþjálfa en þremur þáttum var ekki nægilega vel mætt að mati þátttakenda. Af þessum niðurstöðum er hægt að sjá hvernig best er að haga þjónustunni eftir þörfum og óskum skjólstæðinga Lykilhugtök: Endurhæfing, skjólstæðingsmiðuð iðjuþjálfun, skjólstæðingar iðjuþjálfa, viðhorf og þjónusta iðjuþjálfa

Reawakening of a volcano: Activity beneath Eyjafjallajökull volcano from 1991 to 2009

The ice-capped Eyjafjallajökull volcano, south Iceland, had been dormant for 170 years when the first signs of reawakening of the volcano were captured by seismic and geodetic measurements in 1994. These were the first clear observed signs of unrest followed by 16 years of intermittent magmatic unrest culminating in 2010 when two eruptions broke out on the flank and at the summit. We analyze seismic data from 1991 through 2008 and GPS data from 1992 to May 2009 to infer magma movements beneath the volcano. The relocated earthquakes reveal an overall pipe-like pattern northeast of the summit crater, sporadically mapping the pathway of magma from the base of the crust towards an intrusion in the upper crust. During the study period, three major seismic swarms were recorded. Two of them, in 1994 and 1999–2000, occurred in the upper and intermediate crust and accompanied crustal deformation centered at the southeastern flank. No uplift was detected during the 19- to 25-km-deep 1996 swarm, near the crust–mantle boundary, but the horizontal, ~ E–W oriented T-axes indicate a period of tension/opening, suggesting magma intruding up into the base of the crust. The GPS measured deformation during 1999–2000 can be modeled as intrusion of a horizontal, circular sill with volume of 0.030 ± 0.007 km3 at 5.0 ± 1.3 km depth. The less constrained 4.5- to 5-km-deep sill model for the 1994 episode indicates a three times smaller intruded volume (0.011 km3) than during 1999–2000. In the years between/following the intrusions, contraction was observed at the southeastern flank. The contraction from 2000.5 to 2009.3 can be fitted by a circular sill model with a volume contraction of − 0.0015 ± 0.0003 km3/year at 5.5 ± 2.0 km depth. The less well constrained model for 1994.7 to 1998.6 gives a volume contraction of –(0.0009–0.0010) km3 at a fixed depth of 5 km. The accumulated volume changes (~− 0.013 km3 for the second period, ~ 0.0037 km3 for the first period) are much larger than expected due to solidification and cooling of magma alone and might partly be explained by the underestimated volume of intruded magma, mass loading effects within the crust due to the intruded magma and possibly, and to less extent, degassing (CO2)

Ómskoðun legs og blæðingar í sængurlegu

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenWomen with secondary postpartum hemorrhage are increasingly sent for ultrasound examination to help the clinician decide whether or not surgical curettage will be necessary. A retrospective study of secondary postpartum hemorrhage among women admitted to the National University Hospital (year 1991) was done; 48 women (1.6% of deliveries) were admitted because of postpartum hemorrhage, uterine infection or suspicion of retained placental tissue; 71% presented with hemorrhage. All except one had ultrasound examinations. Surgical curettage was done in 79%. In 17 cases were specimens obtained for histologic examination, showing retained placental tissue in 14 cases. Forty women with an uncomplicated delivery and puerperium (20 primiparas and 20 multiparas), were selected for a prospective study of the sonographic appearance of the normal puerperal uterus. Ultrasound examinations were done on the 5. and 14. day after delivery. A significant reduction in uterine size was found between the first and second examination (p<0.0001). The mean reduction of uterine volume was 443 ml (range 154-833 ml). There was no significant difference between primiparas and multiparas. In 34 instances the uterine cavity appeared empty on the 5. day, but hypoechoic material was seen in 4 women. In 12 there was hypoechoic material in the uterine cavity on the 14. day where the uterine cavity had appeared empty on the 5. day. On the 14. day there was no significant difference in uterine volume between cases with hypoechoic material and those who had an empty uterine cavity. The normal puerperal uterus has a diverse ultrasonic appearance. Ultrasound results should not be an important factor when a patient with secondary postpartum hemorrhage is being considered for curettage. Further research is necessary to explain the ultrasonic appearance of the puerperal uterus.Tilgangur: Í sængurlegu er ómskoðun notuð til að athuga hvort fylgjuleifar eða merki um blóðhlaup sjáist í leginu. Til að fá vitneskju um eðlilega stærð og útlit legs hjá sængurkonum var gerð framsýn athugun á legi með ómskoðun, en algengi og einkenni blæðingavandamála í sængurlegu voru metin með aftursýnni athugun á innlögnum eftir fæðingu. Efniviður: Af konum sem fæddu á árinu 1991 á Kvennadeildinni voru 1,6% með grun um fylgjuleifar eða blóðhlaup í legi. Tíðni aðgerða, ómskoðana og einkenni í þessum tilvikum voru athuguð. Framsýna rannsóknin var gerð á fimmta og 14. degi eftir fæðingu hjá 40 heilbrigðum konum. Leg var mælt í þremur víddum og rúmmál legs og rúmmálsbreyting reiknuð. Niðurstöður: Flestar þeirra kvenna þar sem grunur vaknaði um óeðlilegt innihald í legi fóru í útskaf (79%). Vefjagreining var gerð hjá 17 konum og 14 reyndust vera með fylgjuleifar. Hjá heilbrigðu konunum varð marktæk minnkun á stærð legs frá fyrri að seinni mælingu (p<0,0001). Breyting á rúmmáli nam að meðaltali 443 ml (bil 154¬833 ml). Ekki var munur á legstærð hjá frum- og fjölbyrjum. Í 34 tilvikum virtist leghol vera tómt á fimmta degi, en hjá fjórum konum var ómsnautt innihald í legi og í tveimur ómþétt. Hjá 12 konum sást ómsnautt innihald á 14. degi en ekki við fyrri skoðunina. Ekki var marktækur munur á rúmmáli legs á 14. degi hjá þeim konum, þar sem innihald var í legi (M 330 ml, SF 84,5 ml) og þar sem það var ekki (M 296 ml, SF 84,5 ml). Ályktun: Blæðing frá legi í sængurlegu er algengt vandamál, en þó innihald sjáist í legi við ómskoðun þarf sjúkdómsástand ekki að vera til staðar. Ákvörðun um það hvort kona fer í aðgerð eða ekki á að byggjast á klínísku mati, en ómskoðun getur veitt viðbótarupplýsingar

Ómskoðun legs og blæðingar í sængurlegu

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenWomen with secondary postpartum hemorrhage are increasingly sent for ultrasound examination to help the clinician decide whether or not surgical curettage will be necessary. A retrospective study of secondary postpartum hemorrhage among women admitted to the National University Hospital (year 1991) was done; 48 women (1.6% of deliveries) were admitted because of postpartum hemorrhage, uterine infection or suspicion of retained placental tissue; 71% presented with hemorrhage. All except one had ultrasound examinations. Surgical curettage was done in 79%. In 17 cases were specimens obtained for histologic examination, showing retained placental tissue in 14 cases. Forty women with an uncomplicated delivery and puerperium (20 primiparas and 20 multiparas), were selected for a prospective study of the sonographic appearance of the normal puerperal uterus. Ultrasound examinations were done on the 5. and 14. day after delivery. A significant reduction in uterine size was found between the first and second examination (p<0.0001). The mean reduction of uterine volume was 443 ml (range 154-833 ml). There was no significant difference between primiparas and multiparas. In 34 instances the uterine cavity appeared empty on the 5. day, but hypoechoic material was seen in 4 women. In 12 there was hypoechoic material in the uterine cavity on the 14. day where the uterine cavity had appeared empty on the 5. day. On the 14. day there was no significant difference in uterine volume between cases with hypoechoic material and those who had an empty uterine cavity. The normal puerperal uterus has a diverse ultrasonic appearance. Ultrasound results should not be an important factor when a patient with secondary postpartum hemorrhage is being considered for curettage. Further research is necessary to explain the ultrasonic appearance of the puerperal uterus.Tilgangur: Í sængurlegu er ómskoðun notuð til að athuga hvort fylgjuleifar eða merki um blóðhlaup sjáist í leginu. Til að fá vitneskju um eðlilega stærð og útlit legs hjá sængurkonum var gerð framsýn athugun á legi með ómskoðun, en algengi og einkenni blæðingavandamála í sængurlegu voru metin með aftursýnni athugun á innlögnum eftir fæðingu. Efniviður: Af konum sem fæddu á árinu 1991 á Kvennadeildinni voru 1,6% með grun um fylgjuleifar eða blóðhlaup í legi. Tíðni aðgerða, ómskoðana og einkenni í þessum tilvikum voru athuguð. Framsýna rannsóknin var gerð á fimmta og 14. degi eftir fæðingu hjá 40 heilbrigðum konum. Leg var mælt í þremur víddum og rúmmál legs og rúmmálsbreyting reiknuð. Niðurstöður: Flestar þeirra kvenna þar sem grunur vaknaði um óeðlilegt innihald í legi fóru í útskaf (79%). Vefjagreining var gerð hjá 17 konum og 14 reyndust vera með fylgjuleifar. Hjá heilbrigðu konunum varð marktæk minnkun á stærð legs frá fyrri að seinni mælingu (p<0,0001). Breyting á rúmmáli nam að meðaltali 443 ml (bil 154¬833 ml). Ekki var munur á legstærð hjá frum- og fjölbyrjum. Í 34 tilvikum virtist leghol vera tómt á fimmta degi, en hjá fjórum konum var ómsnautt innihald í legi og í tveimur ómþétt. Hjá 12 konum sást ómsnautt innihald á 14. degi en ekki við fyrri skoðunina. Ekki var marktækur munur á rúmmáli legs á 14. degi hjá þeim konum, þar sem innihald var í legi (M 330 ml, SF 84,5 ml) og þar sem það var ekki (M 296 ml, SF 84,5 ml). Ályktun: Blæðing frá legi í sængurlegu er algengt vandamál, en þó innihald sjáist í legi við ómskoðun þarf sjúkdómsástand ekki að vera til staðar. Ákvörðun um það hvort kona fer í aðgerð eða ekki á að byggjast á klínísku mati, en ómskoðun getur veitt viðbótarupplýsingar

i0091-7613-36-1-3.indd

ABSTRACT We modeled global positioning system measurements of crustal velocity along a N13°E profi le across the southern Adria microplate and south-central Dinarides mountain belt using a one-dimensional elastic dislocation model. We assumed a N77°W fault strike orthogonal to the average azimuth of the measured velocities, but we used a constrained random search algorithm minimizing misfi t to the velocities to determine all other parameters of the model. The model fault plane reaches the surface seaward of mapped SW-verging thrusts of Eocene and perhaps Neogene age along the coastal areas of southern Dalmatia, consistent with SW-migrating deformation in an active fold-and-thrust belt. P-wave tomography shows a NE-dipping high-velocity slab to ~160 km depth, which reaches the surface as Adria, dips gently beneath the foreland, and becomes steep beneath the Dinarides topographic high. The thrust plane is located directly above the shallowly dipping part of the slab. The pattern of precisely located seismicity is broadly consistent with both the tomography and geodesy; deeper earthquakes (down to ~70 km) correlate spatially with the slab, and shallower earthquakes are broadly clustered around the geodetically inferred thrust plane. The model fault geometry and loading rate, ages of subaerially exposed thrusts in the fold-and-thrust belt, and the length of subducted slab are all consistent with Adria-Eurasia collision involving uninterrupted subduction of southern Adria mantle lithosphere beneath Eurasia since Eocene time