Beschreibung: SUMMARY Stress wave attenuation across fractured rock masses is a great concern of underground structure safety. This paper presents an analytical study on wave attenuation across parallel fractures at arbitrary incidence angles, where multiple reflections occurring between fractures are taken into account. Combined with displacement discontinuous model, plane wave analysis and propagator matrix method are applied to develop relations between the first layer and the n th layer with respect to potential amplitudes or displacements and stresses in matrix form. With initial and boundary conditions for different scenarios, potential amplitudes in any layer or displacements and stresses at any point can be obtained by solving corresponding matrixes. After parametric studies, it is found that parameters including incidence angle, normalized fracture stiffness, number of fractures, and fracture spacing have obvious effects on wave attenuation across parallel fractures. Copyright © 2011 John Wiley & Sons, Ltd.

Beschreibung: In the 2002-2003 severe acute respiratory syndrome coronavirus (SARS-CoV) epidemic, no patients under 24 years of age died, while mortality was greater than 50% in those over 65 years. Greater than 90% of all deaths from influenza A virus (IAV) occur in the elderly (〉65 years of age). To address this age-related susceptibility to SARS-CoV and IAV, we infected C57BL/6 (B6) mice with mouse-adapted SARS-CoV (MA15) or IAV (PR8), both of which cause severe disease in aged mice. Intranasal pretreatment of aged mice with poly(I·C) (a TLR3 agonist) and, to a lesser extent, CpG, R848, or lipopolysaccharide (TLR9, TLR7/8, or TLR4 agonists), provided a high level of protection [90% to 100% survival rate after poly(I·C) treatment] against lethal MA15 or IAV challenge and reduced pathological changes and virus loads in the lungs at early times after infection. Poly(I·C) pretreatment upregulated beta interferon (IFN-β), IFN-, IL-1β, and tumor necrosis factor (TNF) gene expression in the lungs. Intranasal pretreatment with IFN-β or IFN- but not IL-1β or TNF also protected aged mice, consistent with the notion that poly(I·C) pretreatment functioned, at least in part, by inducing IFN-β and IFN-. We also identified a potential cellular target for poly(I·C) by showing that treatment inhibited virus replication in primary human airway epithelial cells. These results suggest that intranasal poly(I·C) should be evaluated as a prophylactic agent in aged individuals at high risk for contracting SARS-CoV or IAV infections.

Beschreibung: The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region called Tibetan Plate was found in northern and eastern Tibet between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic velocity (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy. The crustal shortening in the southern Tibet is accommodated by underthrusting of the Indian crust below the Asian crust that may reach further north than the YZS. In northern Tibet, crustal shortening is accommodated by homogeneous crustal thickening. The more rugged and higher topography in west Tibet can be supported by the rigid mantle lithosphere there, whereas to the east the lithosphere is weaker due to the existence of the crush zone. Under pressure by Indian and Asian plates, the subducted Indian lithospheric materials moved eastward and divided into four directions when meeting the Sichuan basin, two horizontal (southeastern ward forming Yun-Gui-Chuan plateau, northeastern ward to Erdos) and two vertical(upward forming Longmen Shan and down ward entering deep mantle).

Beschreibung: Receiver function image along a temporary seismic array (ANTILOPE-2) reveals detailed information of the underthrusting of the Indian crust beneath southern Tibet. The Moho dips northward from _50 km to 80 km depth beneath Himalaya terrane and reaches locally a depth of 90 km beneath the Indus-Yalung suture (IYS). It remains at _80 km in Lhasa terrane and shallows to _70 km in Qiangtang terrane. A lower crustal interface at _60 km depth beneath Lhasa terrane can be clearly followed southward through the Main-Himalaya-Thrust (MHT) and connects the Main-Boundary-Thrust (MBT) at the surface, which represents the border of the Indian crust that is underthrusting the Tibetan crust until south of Bangong-Nujiang Suture (BNS) at _32_N. We also observed a wide-spread mid-crustal low velocity zone with increasing depth from _15 km in Lhasa terrane southward to _35 km beneath high Himalaya that is terminated at the MHT. The low-velocity zone is thought to be formed by partial melt and/or aqueous fluids.

Beschreibung: Seismic images of the architecture of the colliding plates in Tibet are still controversial. Especially the northern limit of the mantle part of the lithosphere of the subducting Indian plate is not well known. The use of increasingly sophisticated seismic technologies yields new images that have significant implications for our understanding of the evolution and ongoing dynamics of the collision of the Indian and Asian plates. We herein present direct observations of the plate structure beneath the Tibetan plateau, by inspection of converted seismic waves. By assembling sections of P-S and S-P converted waves we have mapped the Indian and Asian plates along a number of profiles that traverse the plateau. We have furthermore identified a Tibetan plate that forms a distinct Lithospheric block, and is sandwiched between the Asian and Indian plates. In the westernmost part of Tibet, the Asian plate is underthrusting beneath the Indian plate, while in central and eastern Tibet the Indian plate is underthrusting beneath the Tibetan plate. There are indications of Asian plate subduction in northern Tibet that are connected with a thickening of the Tibetan Plate. The seismic velocities in the Tibetan plate are slower than in the Indian and Asian plates, suggesting a significant temperature difference and hence different rheological behavior in the post-Collision deformation of the Tibetan plate.

Beschreibung: A moment magnitude (Mw) 6.2 earthquake struck beneath the outer suburbs of Christchurch, New Zealand's second largest city, on 22 February 2011 local time. The Christchurch earthquake was the deadliest in New Zealand since the 1931 Mw 7.8 Hawkes Bay earthquake and the most expensive in New Zealand's recorded history. The effects of the earthquake on the region's population and infrastructure were severe including 181 fatalities, widespread building damage, liquefaction and landslides. The Christchurch earthquake was an aftershock of the Mw 7.1 Darfield Earthquake of September 2010, occurring towards the eastern edge of the aftershock zone. This was a low recurrence earthquake for New Zealand and occurred on a fault unrecognised prior to the Darfield event. Geodetic and seismological source models show that oblique-reverse slip occurred along a northeast–southwest-striking fault dipping southeast at c. 69°, with maximum slip at 3–4 km depth. Ground motions during the earthquake were unusually large at near-source distances for an earthquake of its size, registering up to 2.2 g (vertical) and 1.7 g (horizontal) near the epicentre and up to 0.8 g (vertical) and 0.7 g (horizontal) in the city centre. Acceleration response spectra exceeded 2500 yr building design codes and estimates based on standard New Zealand models. The earthquake was associated with high apparent stress indicative of a strong fault. Furthermore, rupture in an updip direction towards Christchurch likely led to strong directivity effects in the city. Site effects including long period amplification and near-surface effects also contributed to the severity of ground motions.

Beschreibung: The fate of the colliding Indian and Asian tectonic plates below the Tibetan high plateau may be visualized by, in addition to seismic tomography, mapping the deep seismic discontinuities, like the crust-mantle boundary (Moho), the lithosphere-asthenosphere boundary (LAB), or the discontinuities at 410 and 660 km depth. We herein present observations of seismic discontinuities with the P and S receiver function techniques beneath central and western Tibet along two new profiles and discuss the results in connection with results from earlier profiles, which did observe the LAB. The LAB of the Indian and Asian plates is well-imaged by several profiles and suggests a changing mode of India-Asia collision in the east-west direction. From eastern Himalayan syntaxis to the western edge of the Tarim Basin, the Indian lithosphere is underthrusting Tibet at an increasingly shallower angle and reaching progressively further to the north. A particular lithospheric region was formed in northern and eastern Tibet as a crush zone between the two colliding plates, the existence of which is marked by high temperature, low mantle seismic wavespeed (correlating with late arriving signals from the 410 discontinuity), poor Sn propagation, east and southeast oriented global positioning system displacements, and strikingly larger seismic (SKS) anisotropy.