The Seismic Project of the National Tsunami Hazard Mitigation Program     

David H. Oppenheimer  Alex N. Bittenbinder  Barbara M. Bogaert  Raymond P. Buland  Lynn D. Dietz  Roger A. Hansen  Stephen D. Malone  Charles S. McCreery  Thomas J. Sokolowski  Paul M. Whitmore  Craig S. Weaver 《Natural Hazards》2005,35(1):59-72

In 1997, the Federal Emergency Management Agency (FEMA), National Oceanic and Atmospheric Administration (NOAA), U.S. Geological Survey (USGS), and the five western States of Alaska, California, Hawaii, Oregon, and Washington joined in a partnership called the National Tsunami Hazard Mitigation Program (NTHMP) to enhance the quality and quantity of seismic data provided to the NOAA tsunami warning centers in Alaska and Hawaii. The NTHMP funded a seismic project that now provides the warning centers with real-time seismic data over dedicated communication links and the Internet from regional seismic networks monitoring earthquakes in the five western states, the U.S. National Seismic Network in Colorado, and from domestic and global seismic stations operated by other agencies. The goal of the project is to reduce the time needed to issue a tsunami warning by providing the warning centers with high-dynamic range, broadband waveforms in near real time. An additional goal is to reduce the likelihood of issuing false tsunami warnings by rapidly providing to the warning centers parametric information on earthquakes that could indicate their tsunamigenic potential, such as hypocenters, magnitudes, moment tensors, and shake distribution maps. New or upgraded field instrumentation was installed over a 5-year period at 53 seismic stations in the five western states. Data from these instruments has been integrated into the seismic network utilizing Earthworm software. This network has significantly reduced the time needed to respond to teleseismic and regional earthquakes. Notably, the West Coast/Alaska Tsunami Warning Center responded to the 28 February 2001 Mw 6.8 Nisqually earthquake beneath Olympia, Washington within 2 minutes compared to an average response time of over 10 minutes for the previous 18 years.  相似文献   

The response of creeping parts of the San Andreas fault to earthquakes on nearby faults: Two examples   总被引：2，自引：0，他引：2  

R. W. Simpson  S. S. Schulz  L. D. Dietz  R. O. Burford 《Pure and Applied Geophysics》1988,126(2-4):665-685

Rates of shallow slip on creeping sections of the San Andreas fault have been perturbed on a number of occasions by earthquakes occurring on nearby faults. One example of such perturbations occurred during the 26 January 1986 magnitude 5.3 Tres Pinos earthquake located about 10 km southeast of Hollister, California. Seven creepmeters on the San Andreas fault showed creep steps either during or soon after the shock. Both left-lateral (LL) and right-lateral (RL) steps were observed. A rectangular dislocation in an elastic half-space was used to model the coseismic fault offset at the hypocenter. For a model based on the preliminary focal mechanism, the predicted changes in static shear stress on the plane of the San Andreas fault agreed in sense (LL or RL) with the observed slip directions at all seven meters; for a model based on a refined focal mechanism, six of the seven meters showed the correct sense of motion. Two possible explanations for such coseismic and postseismic steps are (1) that slip was triggered by the earthquake shaking or (2) that slip occurred in response to the changes in static stress fields accompanying the earthquake. In the Tres Pinos example, the observed steps may have been of both the triggered and responsive kinds. A second example is provided by the 2 May 1983 magnitude 6.7 Coalinga earthquake, which profoundly altered slip rates at five creepmeters on the San Andreas fault for a period of months to years. The XMM1 meter 9 km northwest of Parkfield, California recorded LL creep for more than a year after the event. To simulate the temporal behavior of the XMM1 meter and to view the stress perturbation provided by the Coalinga earthquake in the context of steady-state deformation on the San Andreas fault, a simple time-evolving dislocation model was constructed. The model was driven by a single long vertical dislocation below 15 km in depth, that was forced to slip at 35 mm/yr in a RL sense. A dislocation element placed in the seismogenic layer under XMM1 was given a finite breaking strength of sufficient magnitude to produce a Parkfield-like earthquake every 22 years. When stress changes equivalent to a Coalinga earthquake were superposed on the model running in a steady state mode, the effect was to make a segment under XMM1, that could slip in a linear viscous fashion, creep LL and to delay the onset of the next Parkfield-like earthquake by a year or more. If static stress changes imposed by earthquakes off the San Andreas can indeed advance or delay earthquakes on the San Andreas by months or years, then such changes must be considered in intermediate-term prediction efforts.  相似文献   

LAGUNA GUATAVITA: NOT METEORITIC,PROBABLE SALT COLLAPSE CRATER     

Robert S. Dietz  John F. McHone 《Meteoritics & planetary science》1972,7(3):303-307

Laguna Guatavita (Colombia), a crater 700 m across and 125 m deep containing a central lake, appears not to be a meteorite crater as widely supposed. The tectonic style is not that of an impact site and there is no raised rim or ejected debris. We could find no impactite, shock metamorphic effects or shock fractures (shatter cones). Most likely it is a collapsed crater caused by the solution and withdrawal of salt from an underlying anticline  相似文献   

Nonlinear behavior simulation of soil-structure interaction system via real-time hybrid testing     

Tang  Zhenyun  Liu  Hao  Dietz  Matt  Chatzigogos  Charisis T.  Du  Xiuli 《Bulletin of Earthquake Engineering》2022,20(11):6109-6128

Bulletin of Earthquake Engineering - Soil-structure interaction (SSI) can potentially compromise structures that are subjected to seismic excitation. In recent years, real-time hybrid testing...  相似文献   

Circumstellar molecular line absorption and emission in the optical spectra of post-AGB stars     

Eric J. Bakker  Henny J. G. L. M. Lamers  L. B. F. M. Waters  Ton Schoenmaker 《Astrophysics and Space Science》1995,231(1-2):335-338

We present preliminary results obtained with the European Observation Network. This network consists of 9 observatories in the Czech Republic, Germany and Bulgaria and has been involved in the BACODINE activities since April 1, 1994. We also discuss related problems such as the background of unknown variable stars and suggest a strategy for work in this area.  相似文献   

Numerical simulation of dynamic soil–structure interaction in shaking table testing     

Dimitris Pitilakis  Matt Dietz  David Muir Wood  Didier Clouteau  Arezou Modaressi 《Soil Dynamics and Earthquake Engineering》2008,28(6):453-467

This paper provides an insight into the numerical simulation of soil–structure interaction (SSI) phenomena studied in a shaking table facility. The shaking table test is purposely designed to confirm the ability of the numerical substructure technique to simulate the SSI phenomenon. A model foundation–structure system with strong SSI potential is embedded in a dry bed of sand deposited within a purpose designed shaking-table soil container. The experimental system is subjected to a strong ground motion. The numerical simulation of the complete soil–foundation–structure system is conducted in the linear viscoelastic domain using the substructure approach. The matching of the experimental and numerical responses in both frequency and in time domain is satisfying. Many important aspects of SSI that are apparent in the experiment are captured by the numerical simulation. Furthermore, the numerical modelling is shown to be adequate for practical engineering design purposes.  相似文献   

Experimental and computational synergy for modelling an advanced gas-cooled reactor core under seismic excitation     

Luiza Dihoru  Olafur Oddbjornsson  Ben Cannell  Adam J. Crewe  Tony Horseman  Matt Dietz  Colin A. Taylor 《地震工程与结构动力学》2020,49(13):1308-1328

The advanced gas-cooled reactors (AGRs) are the backbone of the United Kingdom's nuclear generation fleet, producing approximately 17% of the country's electricity. Their safety cases are supported by thorough inspection and monitoring of their graphite cores and extensive theoretical, analytical, and experimental studies. This paper presents a unique, highly innovative and technically challenging earthquake engineering project that has provided vital evidence to underpin the seismic safety assessments of the AGRs. Two modelling approaches, one experimental (a multilayer array physical model), and one numerical (a SOLFEC nonsmooth contact dynamics computational model) have been developed to investigate the seismic behaviour of an aged graphite core. The synergetic relationship between the two approaches is a product of insightful collaborative learning between the University of Bristol and Atkins, with the experiments providing material parameters and validation data and the computer simulations feeding array design and test schedule recommendations to the physical model. The predictive capabilities of the physical and the numerical models are tested by direct comparison and the good agreement between the results has increased the confidence in both. The model's versatility allows a variety of core scenarios to be tested that can explore in detail the AGR core behaviour in seismic conditions.  相似文献   

Effects of the middle Holocene high sea-level stand and climate on Amazonian mangroves     

Marcelo C. L. Cohen  Paloma Maria Pinto Camargo  Luiz C. R. Pessenda  Flávio Lima Lorente  Adriana V. De Souza  José Augusto Martins Corrêa  José Bendassolli  Marianne Dietz 《第四纪科学杂志》2021,36(6):1013-1027

The high sea-level stand during the mid-Holocene is a benchmark in mangrove dynamics along the north-east/south-east coast of Brazil and provides a reference point for landward and seaward mangrove migrations corresponding to changes in relative sea level (RSL). However, evidence of the impacts associated with RSL fall on the northern Brazilian coast is scarce. Multi-proxy data from the highest tidal flats of the Bragança Peninsula in northern Brazil revealed modern herbaceous areas were occupied by mangroves Rhizophora and Avicennia from ~6250 to ~5850 cal a bp , and only Avicennia between ~5850 and ~5000 cal a bp . The same tidal flats were vegetation-free between ~5000 and ~4300 cal a bp . A combination of a high sea-level stand (0.6 ± 0.1 m) at ~5000 cal a bp and a dry early–middle Holocene in the Amazon probably caused an increase in porewater salinity of tidal flats, which resulted in a mangrove succession from Rhizophora to Avicennia dominance. RSL fall accentuated this process, contributing to mangrove degradation between ~5000 and ~4300 cal a bp . RSL fall, and a wetter period over the past ~4300 cal a bp caused a mangrove migration from highest to lowest flats, followed by expansion of herbaceous vegetation on the highest flats.  相似文献   

Modeling Geochemically Caused Permanent Stratification in Lake Waldsee (Germany)     

Santiago Moreira  Bertram Boehrer  Martin Schultze  Severine Dietz  Javier Samper 《Aquatic Geochemistry》2011,17(3):265-280

A geochemical model was incorporated into a stratification model for lakes to create the model package: DYCD-CORE, a numerical code that couples the thermal and hydrodynamic capabilities of DYRESM and the geochemical capabilities of the reactive transport model CORE^2D V4. Based on the chemical composition of solutes calculated in each node for each time step, density was computed using specific partial molal volumes of all considered solutes and fed back into the stratification module of the program package. The density calculated each time step leads to a strong coupling of hydrodynamics and hydrogeochemistry and reflects the complex interaction as it is present in all lakes. To demonstrate the functionality of the numerical approach, an example of an iron-meromictic lake was chosen, where the reactivity of the dissolved iron kept the water body perennially stratified. To critically validate the model results, temperatures were continously measured at high vertical and temporal resolution in a field investigation of Waldsee (near Döbern, Germany). Multiparameterprobe profiles and water samples confirmed the continous chemical stratification and served as initial and boundary conditions for the simulation period. The model package DYCD-CORE could reproduce the permanent stratification as it were in the lake. A demonstration run using the standard UNESCO equation for density, and hence assuming non-reactive solutes, failed entirely. Hence, stratification models using salinity for density are not suited for simulating density created by lake-internal geochemical transformation of solutes. However, density can be based directly on the simultaneous numerical simulation of lake geochemistry. Predictive modeling of changing lake circulation in a variable climate or considering change of use will require a proper inclusion of the geochemistry as demonstrated in this paper.  相似文献   

ON THE TERRESTRIAL ORIGIN OF THE TEPEXITL CRATER,MEXICO     

Lucrecia Maupom  Romn Alvarez  Susan W. Kieffer  Robert S. Dietz 《Meteoritics & planetary science》1975,10(3):209-214

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