Megacities – megarisks     

Friedemann Wenzel  Fouad Bendimerad  Ravi Sinha 《Natural Hazards》2007,42(3):481-491

We review the definitions, population trends, and characteristics of megacities. Characteristics of megacities are, apart from their size, their complexity in terms of administration, infrastructure, traffic, etc., and at the same time the speed of change. Vulnerabilities and risk potential are discussed using the examples of Mexico City and Mumbai. We present the experience accumulated in the 6 years work of the Earthquakes and Megacities Initiative (EMI, ) with more than 20 large cities around the world, mostly located in the developing world. On this background we analyze obstacles that keep megacities from developing an efficient approach towards disaster mitigation and define a strategy that might overcome these problems. The key element of this strategy is the development of a Disaster Risk Management Master Plan (DRMMP) for cities. Currently the Istanbul Earthquake Master Plan (IEMP) serves as best example for an appropriate strategy for disaster reduction in megacities.  相似文献   

Rapid Earthquake Information for Bucharest     

Friedemann Wenzel  Gheorge Marmuraenu 《Pure and Applied Geophysics》2007,164(5):929-939

Advances in sensor techniques, digital acquisition, communication and computing allowed establishment of the field of real-time seismology (Kanamori et al., 1997) and the design of earthquake information systems that provide rapid information on ground motion and potential damage in an area for which a ground motion estimation data base is available and where the inventory of buildings and infrastructure and its vulnerability to shaking is known. We discuss a system for the Romanian capital of Bucharest, where an early warning system with about 30 seconds lead time, shake maps and a sophisticated damage estimation tool for Bucharest have been developed in the frame of the Collaborative Research Center on Strong Earthquakes ().  相似文献   

Low Free-Field Accelerations of the 1999 Kocaeli Earthquake?     

Joachim?MiksatEmail author  Friedemann?Wenzel  Vladimir?Sokolov 《Pure and Applied Geophysics》2005,162(5):857-874

The August 17, 1999 Kocaeli earthquake ruptured the earths surface along 145 km and produced a magnitude of M_w=7.4. As expected for such an event Modified Mercalli intensities of typically IX and X in the vicinity of the fault were determined. Yet the observed accelerations at the five near-fault sites remained amazingly small with horizontal PGA values of 0.14 g to 0.4 g. We attempt to resolve the enigma by modeling surface ground motion with a finite-difference algorithm, utilizing two different rupture and slip histories derived from the strong-motion observations and translate the computed horizontal motion in intensity values. We can show that (a) in a given simple crustal velocity model different slip distributions result in significantly different ground motion distributions in the vicinity of the fault even though both slip distributions fit the observed accelerometer data quite well. (b) Both slip distributions project high ground motion into areas adjacent to the fault where no accelerometer was located. (c) Both slip distributions are not fully compatible with observed intensity observations around the fault, although this could be partly attributed to the lack of knowledge regarding to the crustal structure. In the light of our results it would thus be misleading if the few strong-motion observations around the Kocaeli earthquake fault were taken as typical or representative for the entire area and for potential future events.  相似文献   

Equal Spacing of Strike-Slip Faults     

A. M. Merzer  R. Freund 《Geophysical Journal International》1976,45(1):177-188

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Influence of ground-motion correlation on probabilistic assessments of seismic hazard and loss: sensitivity analysis   总被引：2，自引：0，他引：2  

Vladimir Sokolov  Friedemann Wenzel 《Bulletin of Earthquake Engineering》2011,9(5):1339-1360

Recent studies have shown that the proper treatment of ground-motion variability and, particularly, the correlation of ground motion are essential for the estimation of the seismic hazard, damage and loss for distributed portfolios. In this work we compared the effects of variations in the between-earthquake correlation and in the site-to-site correlation on probabilistic estimations of seismic damage and loss for the extended objects (hypothetical portfolio) and critical elements (e.g. bridges) of a network. Taiwan Island has been chosen as a test case for this study because of relatively high seismicity and previous experience in earthquake hazard modelling. The hazard and loss estimations were performed using Monte Carlo approach on the basis of stochastic catalogues and random ground-motion fields. We showed that the influence of correlation on parameters of seismic hazard, characteristics of loss distribution and the probability of damage depend, on one hand, on level of hazard and probability level of interest (return period) and, on the other hand, the relative influence of each type of correlation is not equal.  相似文献   

Cloudy circumstellar dust shells around young variable stars     

C. Friedemann  H. -G. Reimann  J. Gürtler 《Astrophysics and Space Science》1994,212(1-2):221-229

A number of variable stars of the Orion population has been identified with IRAS point sources by us. This finding supports the conclusion that the prominent Algol-like minima in the lightcurves of these stars originate from obscurations by dust clouds in a circumstellar shell. The discussion of the existingUBVR data leads to the remarkable conclusion that the extinction properties of the grain populations contained in individual dust clouds moving in one and the same circumstellar shell are quite different.From the multicolour photometric data of the different Algol-like minima we derived individual values of the reddening parameterR = A _v /E(B - V). It covers a remarkable wide range of values from that one typical of the interstellar extinction law up to 7. In the case of SV Cep one of the grain populations produces a virtually neutral extinction. The large values ofR speak in favour of larger than normal (interstellar) dust grains, which may have grown by coagulation processes. The cloudy circumstellar dust shell provides a natural explanation for the observed infrared excess. The properties derived from the optical light variations are fully compatible with the properties deduced from the infrared radiation. The irregularity of the light variations indicates that many clouds are involved and may sometimes superimpose themselves.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A.  相似文献   

Further analysis of the influence of site conditions and earthquake magnitude on ground-motion within-earthquake correlation: analysis of PGA and PGV data from the K-NET and the KiK-net (Japan) networks   总被引：1，自引：0，他引：1  

Vladimir Sokolov  Friedemann Wenzel 《Bulletin of Earthquake Engineering》2013,11(6):1909-1926

We analyzed the within-earthquake correlation (peak ground acceleration PGA and velocity PGV) in Japan by taking into account local geological conditions. The database includes more than 23,700 records (K-NET and the KiK-net networks) from 84 events (M 4.2–7.4) occurring in 1999–2011. The correlation structure was investigated for residuals obtained using two recently developed ground-motion models for Japan. We have shown that the level of within-earthquake correlation may vary significantly depending on site classes, general geological conditions and earthquake magnitude. The results of the analysis are in general agreement with the findings obtained recently for Taiwan (Sokolov et al. in Bull Earthq Eng 10(5):1401–1429, 2012. doi:10.1007/s10518-012-9368-5). The high level of ground-motion correlation reflects the presence of a non-random component in the residuals that may be caused by the joint influence of surface soil and thick sediments, and this influence depends on the earthquake magnitude. Therefore, a single generalized model of within-earthquake correlation across geologically heterogeneous regions may not be adequate. The application of empirical correction factors, which may be a function of earthquake magnitude, source-to-site distance, site class, and average shear-wave velocity for a given station, allows for effective reduction in the level of within-earthquake correlation.  相似文献   

Ground-motion prediction equations for the intermediate depth Vrancea (Romania) earthquakes   总被引：2，自引：1，他引：1  

Vladimir Sokolov  Klaus-Peter Bonjer  Friedemann Wenzel  Bogdan Grecu  Mircea Radulian 《Bulletin of Earthquake Engineering》2008,6(3):367-388

We present the regional ground-motion prediction equations for peak ground acceleration (PGA), peak ground velocity (PGV), pseudo-spectral acceleration (PSA), and seismic intensity (MSK scale) for the Vrancea intermediate depth earthquakes (SE-Carpathians) and territory of Romania. The prediction equations were constructed using the stochastic technique on the basis of the regional Fourier amplitude spectrum (FAS) source scaling and attenuation models and the generalised site amplification functions. Values of considered ground motion parameters are given as the functions of earthquake magnitude, depth and epicentral distance. The developed ground-motion models were tested and calibrated using the available data from the large Vrancea earthquakes. We suggest to use the presented equations for the rapid estimation of seismic effect after strong earthquakes (Shakemap generation) and seismic hazard assessment, both deterministic and probabilistic approaches.  相似文献   

Solar Eclipses and the Surface Properties of Water     

Fuchs  Elmar C.  Oudakker  Gerrit  Justinek  Martin  Dyer  Nigel  Woisetschläger  Jakob  Godines  Kevin  Mäder  Matthias  Freund  Friedemann T. 《Earth, Moon, and Planets》2019,123(1-2):15-43

Earth, Moon, and Planets - During four solar eclipse events (two annular, one total and one partial) a correlation was observed between a change in water surface tension and the magnitude of the...  相似文献   

Earthquake chemical precursors in groundwater: a review     

Shukra Raj Paudel  Sushant Prasad Banjara  Amrita Wagle  Friedemann T. Freund 《Journal of Seismology》2018,22(5):1293-1314

We review changes in groundwater chemistry as precursory signs for earthquakes. In particular, we discuss pH, total dissolved solids (TDS), electrical conductivity, and dissolved gases in relation to their significance for earthquake prediction or forecasting. These parameters are widely believed to vary in response to seismic and pre-seismic activity. However, the same parameters also vary in response to non-seismic processes. The inability to reliably distinguish between changes caused by seismic or pre-seismic activities from changes caused by non-seismic activities has impeded progress in earthquake science. Short-term earthquake prediction is unlikely to be achieved, however, by pH, TDS, electrical conductivity, and dissolved gas measurements alone. On the other hand, the production of free hydroxyl radicals (?OH), subsequent reactions such as formation of H₂O₂ and oxidation of As(III) to As(V) in groundwater, have distinctive precursory characteristics. This study deviates from the prevailing mechanical mantra. It addresses earthquake-related non-seismic mechanisms, but focused on the stress-induced electrification of rocks, the generation of positive hole charge carriers and their long-distance propagation through the rock column, plus on electrochemical processes at the rock-water interface.  相似文献