Changes to the drivers of fire weather with a warming climate – a case study of southeast Tasmania     

Michael R. Grose  Paul Fox-Hughes  Rebecca M. B. Harris  Nathaniel L. Bindoff 《Climatic change》2014,124(1-2):255-269

Projected changes to the global climate system have great implications for the incidence of large infrequent fires in many regions. Here we examine the synoptic-scale and local-scale influences on the incidence of extreme fire weather days and consider projections of the large-scale mean climate to explore future fire weather projections. We focus on a case study region with periodic extreme fire dangers; southeast Tasmania, Australia. We compare the performance of a dynamically downscaled regional climate model with Global Climate Model outputs as a tool for examining the local-scale influences while accounting for high regional variability. Many of the worst fires in Tasmania and the southeast Australian region are associated with deep cold fronts and strong prefrontal winds. The downscaled simulations reproduce this synoptic type with greater fidelity than a typical global climate model. The incidence of systems in this category is projected to increase through the century under a high emission scenario, driven mainly by an increase in the temperature of air masses, with little change in the strength of the systems. The regional climate model projected increase in frequency is smaller than for the global climate models used as input, with a large model range and natural variability. We also demonstrate how a blocking Foehn effect and topographic channelling contributed to the extreme conditions during an extreme fire weather day in Tasmania in January 2013. Effects such as these are likely to contribute to high fire danger throughout the century. Regional climate models are useful tools that enable various meteorological drivers of fire danger to be considered in projections of future fire danger.  相似文献   

Trends in Abundance Indices of Fishes in Maryland’s Coastal Bays During 1972–2009     

Jennifer Pincin  Michael J. Wilberg  Lora Harris  Angel Willey 《Estuaries and Coasts》2014,37(4):791-800

Maryland’s coastal bays provide habitat for juveniles of many commercially and recreationally important species of shellfish and finfish. Since 1972, the Maryland Department of Natural Resources has conducted the Maryland Coastal Bays Trawl and Seine Survey to monitor the populations of key species. The survey has undergone substantial spatial and methodological changes affecting the interpretation of simple indices of abundance. We developed generalized linear models to standardize the indices of abundance of five commonly caught fish species: Atlantic menhaden Brevoortia tyrannus, weakfish Cynoscion regalis, spot Leiostomus xanthurus, bay anchovy Anchoa mitchilli, and summer flounder Paralichthys dentatus. Density declined significantly since 1972 for menhaden, bay anchovy, and spot in at least one region within the coastal bays. The northern bays had significantly higher densities than the southern bays for all species. Changes in abundance indices of the five species examined were not related to sea grass coverage, temperature, salinity, nitrogen-to-phosphorus ratios, and other habitat variables but were likely a result of stock-wide recruitment processes.  相似文献   

Discovery of possible mega-thrust earthquake along the Seram Trough from records of 1629 tsunami in eastern Indonesian region   总被引：1，自引：1，他引：0  

Zac Yung-Chun Liu  Ron A. Harris 《Natural Hazards》2014,72(3):1311-1328

Arthur Wichmann’s “Earthquakes of the Indian Archipelago” documents several large earthquakes and tsunami throughout the Banda Arc region that can be interpreted as mega-thrust events. However, the source regions of these events are not known. One of the largest and well-documented events in the catalog is the great earthquake and tsunami affecting the Banda Islands on August 1, 1629. It caused severe damage from a 15-m tsunami that arrived at the Banda Islands about a half hour after violent shaking stopped. The earthquake was also recorded 230 km away in Ambon, but no tsunami is mentioned. This event was followed by at least 9 years of uncommonly frequent seismic activity in the region that tapered off with time, which can be interpreted as aftershocks. The combination of these observations indicates that the earthquake was most likely a mega-thrust event. We use an inverse modeling approach to numerically reconstruct the tsunami, which constrains the likely location and magnitude of the 1629 earthquake. Only, linear numerical models are applied due to the low resolution of bathymetry in the Banda Islands and Ambon. Therefore, we apply various wave amplification factors (1.5–4) derived from simulations of recent, well-constrained tsunami to bracket the upper and lower limits of earthquake moment magnitudes for the event. The closest major earthquake sources to the Banda Islands are the Tanimbar and Seram Troughs of the Banda subduction/collision zone. Other source regions are too far away for such a short arrival time of the tsunami after shaking. Moment magnitudes predicted by the models in order to produce a 15-m tsunami are M_w of 9.8–9.2 on the Tanimbar Trough and M_w 8.8–8.2 on the Seram Trough. The arrival times of these waves are 58 min for Tanimbar Trough and 30 min for Seram Trough. The model also predicts 5-m run-up for Ambon from a Tanimbar Trough source, which is inconsistent with the historical records. Ambon is mostly shielded from a wave generated by a Seram Trough source. We conclude that the most likely source of the 1629 mega-thrust earthquake is the Seram Trough. Only one earthquake >M_w 8.0 is recorded instrumentally from the eastern Indonesia region although high rates of strain (50–80 mm/a) are measured across the Seram section of the Banda subduction zone. Enough strain has already accumulated since the last major historical event to produce an earthquake of similar size to the 1629 event. Due to the rapid population growth in coastal areas in this region, it is imperative that the most vulnerable coastal areas prepare accordingly.  相似文献   

Tephra stratigraphy on the North Icelandic shelf: extending tephrochronology into marine sediments off North Iceland     

Esther Ruth Gudmundsdóttir  Guðrún Larsen  Jón Eiríksson 《Boreas: An International Journal of Quaternary Research》2012,41(4):719-734

Tephra stratigraphical and tephrochronological studies of marine core MD99‐2275 on the North Icelandic shelf have revealed 58 new tephra horizons within the last 7050 cal. a BP, bringing the total number of identified tephra layers to 76. So far, over 100 tephra layers have been identified in the entire core spanning the last 15 000 years. The majority of the newly identified tephra layers are basaltic in composition and originate from the most active volcanic systems in Iceland, namely Grímsvötn, Veidivötn‐Bárdarbunga and Katla. A total of 40 tephra layer land–sea correlations have been made within this time period, of which 16 represent absolutely dated tephra markers. In addition, two tephra marker series are revealed in the marine sediments and in the terrestrial tephra stratigraphy, located between c. 2300–2600 and between 5700–5900 years. For the last 15 000 years, 21 tephra markers have been recognized. The marine tephra layer frequency (TLF) reveals two peaks, within the last 2000 years, and between 5000 and 7000 years ago. It shows the same general characteristics as the terrestrial TLF curve in Iceland, which indicates that marine sediments can yield important information about volcanism in Iceland. This is useful in time segments in which terrestrial records are poor or non‐existent. The study contributes to a high‐resolution tephrochronological framework on the North Icelandic shelf, with core MD99‐2275 representing a potential stratotype section in the area, and for the northern North Atlantic–Nordic Seas region, as well as being an important contribution to the Lateglacial–early Holocene volcanic history of Iceland.  相似文献   

A shallow seismic refraction study of the Versailles cryptoexplosion structure,central Kentucky     

James B. Harris  Daniel R. Jones  R. L. Street 《Meteoritics & planetary science》1991,26(1):47-53

Abstract— The Versailles cryptoexplosion structure, located in central Kentucky, contains a partially brecciated central uplift and a boundary marked by arcuate faulting. Seismic refraction data were used to divide the structure into distinct units on the basis of velocity. A zone of brecciated material shows a decrease in velocity compared with surrounding rocks. Locally thickened strata are present on the flanks of the central uplift. An increase of the bedrock velocity in the area surrounding the structure suggests localized dolomization of fractured bedrock, and a plug of fractured strata near the base of the brecciation appears to be uplifted. Based on the geometry of deformation seen in known impact structures, and the integration of this study with previous geological and geophysical work in the area, it is suggested that our results support the interpretation of the Versailles structure as an eroded astrobleme (Black, 1964b; Seeger, 1972).  相似文献   

underwThe Hawaii-2 Observatory seismic system     

Duennebier  F.K. Harris  D.W. Jolly  J. Babinec  J. Copson  D. Stiffel  K. 《Oceanic Engineering, IEEE Journal of》2002,27(2):212-217

The Hawaii-2 Observatory seismic system is currently transmitting high-quality seismic data from the ocean floor in the central NE Pacific Ocean through Hawaii to the IRIS Data Management Center. The system includes broad-band seismic, geophone, acoustic, and ocean current sensors. The seismic sensors are buried about 0.4 m below the ocean floor to improve coupling to the ocean bottom and to reduce noise levels. The system can be remotely calibrated, leveled and locked, and gains can be changed on command from shore. Data are temporarily stored in the seismic package for retransmission as needed to correct for transmission problems and to prevent loss of data. Data generated are valuable for studies of the Earth's structure and the dynamics of earthquakes  相似文献   

Shaking table tests of a resilient bridge system with precast reinforced concrete columns equipped with springs     

Natalia Reggiani Manzo  Michalis F. Vassiliou  Harris Mouzakis  Efstratios Badogiannis 《地震工程与结构动力学》2022,51(1):213-239

This paper presents the shake table test results of a novel system for the design of precast reinforced concrete bridges. The specimen comprises a slab and four precast columns. The connections are dry and the columns are connected to the slab by an ungrouted tendon. One of the tendon ends is anchored above the slab, in series with a stack of washer springs, while the other end is anchored at the bottom of the column. The addition of such a flexible restraining system increases the stability of the system, while keeping it relatively flexible allowing it to experience negative post-uplift stiffness. It is a form of seismic isolation. Anchoring the tendon within the column, caps the design moment of the foundation, and reduces its size. One hundred and eighty-one shake table tests were performed. The first 180 caused negligible damage to the specimen, mainly abrasion at the perimeter of the column top ends. Hence, the system proved resilient. The 181^st excitation caused collapse, because the tendons unexpectedly failed at a load less than 50% of their capacity (provided by the manufacturer), due to the failure of their end socket. This highlights the importance of properly designing the tendons. The tests were used to statistically validate a rigid body model. The model performed reasonably well never underestimating the median displacement response of the center of mass of the slab by more than 30%. However, the model cannot predict the torsion rotation of the slab that was observed in the tests and is due to imperfections.  相似文献   

Modeling of SMF tsunami hazard along the upper US East Coast: detailed impact around Ocean City,MD   总被引：1，自引：0，他引：1  

Stephan T. Grilli  Christopher O’Reilly  Jeffrey C. Harris  Tayebeh Tajalli Bakhsh  Babak Tehranirad  Saeideh Banihashemi  James T. Kirby  Christopher D. P. Baxter  Tamara Eggeling  Gangfeng Ma  Fengyan Shi 《Natural Hazards》2015,76(2):705-746

  相似文献   

New interpretation of the Franciscan mélange at San Simeon coast,California: tectonic intrusion into an accretionary prism     

Yujiro Ogawa  Ryota Mori  Toshiaki Tsunogae  Yildirim Dilek  Ron Harris 《International Geology Review》2015,57(5-8):824-842

Many concepts and interpretations on the formation of the Franciscan mélange have been proposed on the basis of exposures at San Simeon, California. In this paper, we show the distribution of chaotic rocks, their internal structures and textures, and the interrelationship between the chaotic rocks and the surrounding sandstones (turbidites). Mélange components, particularly blueschists, oceanic rocks, including greenstone, pillow lava, bedded chert, limestone, sandstone, and conglomerate, have all been brecciated by retrograde deformation. The Cambria Slab, long interpreted as a trench slope basin, is also strongly deformed by fluidization, brecciation, isoclinal folding, and thrusting, leading us to a new interpretation that turbiditic rocks (including the Cambria Slab) represent trench deposits rather than slope basin sediments. These rocks form an accretionary prism above mélanges that were diapirically emplaced into these rocks first along sinistral-thrust faults, and then along dextral-normal faults. Riedel shear systems are observed in several orders of scale in both stages. Although the exhumation of the blueschist blocks is still controversial, the common extensional fractures and brecciation in most of the blocks in the mélanges and further mixture of various lithologies into one block with mélange muddy matrix indicate that once deeply buried blocks were exhumed from considerable depths to the accretionary prism body, before being diapirically intruded with their host mélange along thrust and normal faults, during which retrograde deformation occurred together with retrograde metamorphism. Recent similar examples of high-pressure rock exhumation have been documented along the Sofugan Tectonic Line in the Izu forearc areas, in the Mineoka belt in the Boso Peninsula, and as part of accretionary prism development in the Nankai and Sagami troughs of Japan. These modern analogues provide actively forming examples of the lithological and deformational features that characterize the Franciscan mélange processes.  相似文献   

Lost in translation? Interpretations of the probability phrases used by the Intergovernmental Panel on Climate Change in China and the UK     

Adam J. L. Harris  Adam Corner  Juemin Xu  Xiufang Du 《Climatic change》2013,121(2):415-425

  相似文献