Earthquake early warning scenarios at critical facilities in the Eastern Caribbean

A feasibility study of an earthquake early warning (EEW) system was conducted for the Eastern Caribbean region using scenario earthquakes, corresponding to the maximum credible earthquakes and to the earthquakes associated with a return period of 475 years. Broadband synthetic seismograms were produced at selected critical facilities, where there is potential interest in the installation of an EEW system. The expected damage was derived from the synthetic seismograms and compared with the lead-time determined for both a regional and on-site EEW configuration. Next, the Virtual Seismologist EEW algorithm, as included in SeisComP3, was tested. Additional broadband synthetic seismograms were produced for the stations in the Eastern Caribbean seismic networks in order to simulate the real time behaviour of the seismic networks during the occurrence of the synthetic earthquakes and to assess the predictive capacity of the selected ground motion prediction equation. Expected peak ground parameters and lead-times at the critical facilities constitute the major outcome of the study.     

Model‐based evaluation of impact of soil redistribution on soil organic carbon stocks in a temperate hedgerow landscape

Agroforestry systems are promoted for providing a number of ecosystem services and environmental benefits, including soil protection and carbon sequestration. This study proposes a modelling approach to quantify the impact of soil redistribution on soil organic carbon (SOC) storage in a temperate hedgerow landscape. Evolution of SOC stocks at the landscape scale was examined by simulating vertical and horizontal SOC transfers in the 0–105 cm soil layer due to soil redistribution by tillage and water processes. A spatially explicit SOC dynamics model (adapted from RothC‐26.3) was used, coupled with a soil‐redistribution model (LandSoil). SOC dynamics were simulated over 90 years in an agricultural hedgerow landscape dedicated to dairy farming, with a mix of cropping and grasslands. Climate and land use were simulated considering business‐as‐usual scenarios derived from existing information on the study area. A net decrease in SOC stocks was predicted at the end of the simulation period. Soil redistribution induced a net SOC loss equivalent to 2 kg C ha^?1 yr^?1 because of soil exportation out of the study site and an increase in SOC mineralization. Hedgerows and woods were the only land use in which soil redistribution induced net SOC storage. Soil tillage was the main process that induced soil redistribution within cultivated fields. Soil exportation out of the study area was due to erosion by water, but remained low because of the protective role of the hedgerow network. These soil transfers redistributed SOC stocks in the landscape, mostly within cultivated fields. Copyright © 2016 John Wiley & Sons, Ltd.     

Propagation, linkage, and interaction of caldera ring-faults: comparison between analogue experiments and caldera collapse at Miyakejima, Japan, in 2000

The formation of ring faults yields important implications for understanding the structural and dynamic evolution of collapse calderas and potentially associated ash-flow eruptions. Caldera collapse occurred in 2000 at Miyakejima Island (Japan) in response to a lateral intrusion. Based on geophysical data it is inferred that a set of caldera ring faults was propagating upward. To understand the kinematics of ring-fault propagation, linkage, and interaction, we describe new laboratory sand-box experiments that were analyzed through Digital Image Correlation (DIC) and post-processed using 2D strain analysis. The results help us gain a better understanding of the processes occurring during caldera subsidence at Miyakejima. We show that magma chamber evacuation induces strain localization at the lateral chamber margin in the form of a set of reverse faults that sequentially develops and propagates upwards. Then a set of normal faults initiates from tension fractures at the surface, propagating downwards to link with the reverse faults at depth. With increasing amounts of subsidence, interaction between the reverse- and normal-fault segments results in a deactivation of the reverse faults, while displacement becomes focused on the outer normal faults. Modeling results show that the area of faulting and collapse migrates successively outward, as peak displacement transfers from the inner ring faults to later developed outer ring faults. The final structural architecture of the faults bounding the subsiding piston-like block is hence a consequence of the amount of subsidence, in agreement with other caldera structures observed in nature. The experimental simulations provide an analogy to the observations and seismic records of caldera collapse at Miyakejima volcano, but are also applicable to caldera collapse in general.     

Toxicity testing,risk assessment,and options for dredged material management

Programs for evaluating proposed discharges of dredged material into waters of the United States specify a tiered testing and evaluation protocol that includes performance of acute and chronic bioassays to assess toxicity of the dredged sediments. Although these evaluations reflect the toxicological risks associated with disposal activities to some degree, analysis activities are limited to the sediments of each dredging project separately. Cumulative risks to water column and benthic organisms at and near the designated disposal site are therefore difficult to assess. An alternate approach is to focus attention on the disposal site, with the goal of understanding more directly the risks of multiple disposal events to receiving ecosystems. Here we review current US toxicity testing and evaluation protocols, and describe an application of ecological risk assessment that allows consideration of the temporal and spatial components of risk to receiving aquatic ecosystems. When expanded to include other disposal options, this approach can provide the basis for holistic management of dredged material disposal.     

The space debris environment of the Earth

37 years of space activities have led to a large number of anthropogenic objects orbiting the Earth. Ground-based observations with radar and optical facilities reveal the existence of about 7500 objects in space, which do not represent an immediate excessive danger. However, adequate actions are required to keep the long-term debris hazard for manned and unmanned missions within acceptable tolerances. In this paper the space debris environment of the Earth and its future evolution are described. New developments which could have a major impact on the space environment, are the the planned multi-satellite constellations for communications purposes or solar power stations in Earth orbit. Finally, methods for debris reduction are outlined. Space debris is a global problem which can only be effectively solved by international cooperation.     

Latitudinal UVR-PAR measurements in Argentina: extent of the ‘ozone hole’

The UVR-PAR Argentinean Monitoring Network started its operation in September 1994 recording ultraviolet (UVR) and Photosynthetic Available Radiation (PAR) at a frequency of once per minute, at four sites, throughout the entire year. Four spectroradiometers (GUV-511, Biospherical Instruments, Inc.) were installed at research centers separated by about 8–12 degrees of latitude, extending from the Subantarctic-Fueguian region to the Tropic of Capricorn. The instruments are located in populated areas ranging from 30,000 to 11 million people and with extremely different climate regimes and conditions of tropospheric pollution. Our ground-based data indicated that the irradiance increased steadily from south to north. This increase was also observed in the calculated daily doses of UV-B (280–320 nm); however, daily integrated values for UV-A (320–400 nm) and PAR (400–700 nm) were higher at mid-latitudes (Puerto Madryn, 42°47′S). A similar south-to-north increase was evident in the ratio of the energy at 305 nm and 340 nm wavelengths (with low 305/340 ratios indicating high total ozone column concentration), with low values at Ushuaia (55°01′S) and high values at Jujuy (24°10′S). However, the 305/340 ratios increased significantly over their normal spring values at two sites, Ushuaia and Puerto Madryn, for variable time periods during October-December. Our data suggest that the ozone hole was over South America extending to about 38°S for at least a week during October and about two weeks during November-December of the years of 1994 and 1995. However, it should be noted that the erythemal irradiance, in the area influenced by the ozone hole, was at all times lower than that in Buenos Aires and well below the value at Jujuy (tropical station). This study also indicates that when assessing the impact of solar UVR upon organisms, other variables such as cloud cover, solar zenith angle, day length, latitude, and atmospheric pollution should be considered in addition to total ozone column concentration.     

Storm-intensity criteria for several classes of the driving interplanetary structures

In this paper we discuss the main-phase evolution of intense magnetic storms, associated with the passage of different interplanetary magnetic structures. It is shown that their evolution, driven by intense magnetic fields in the sheath region just behind interplanetary shocks, evolves faster (implying physically different magnetospheric configurations) than that associated with intense magnetic fields in the ejecta itself and in corotating streams. The estimated ring-current injection rate for the main phase of intense magnetic storms caused by sheath fields is ～10 times greater than the estimated injection rate for N–S magnetic clouds. Based on these results, we propose storm-intensity criteria for several classes of the driving interplanetary structures. The time necessary to reach a Dst/SYM index threshold level is an important parameter for a space weather forecast.     

3C390．3的弱秒差距尺度喷流及其变化

通过对射电星系３Ｃ３９０．３在历元１９８９．２９及６ｃｍ波长的ＶＬＢＩ观测数据的多软件包成象，辨认出其弱秒差距尺度喷流中几个分离的节，将它们和以前发表及未发表的同一波长的成象结果比较，显示了该源弱秒差距尺度喷流的弯曲和反喷流，并重新证认了喷流中节的视超光速运动。