Prevention of strong earthquakes: Goal or utopia?

In the present paper, we consider ideas suggesting various kinds of industrial impact on the close-to-failure block of the Earth’s crust in order to break a pending strong earthquake (PSE) into a number of smaller quakes or aseismic slips. Among the published proposals on the prevention of a forthcoming strong earthquake, methods based on water injection and vibro influence merit greater attention as they are based on field observations and the results of laboratory tests. In spite of this, the cited proofs are, for various reasons, insufficient to acknowledge the proposed techniques as highly substantiated; in addition, the physical essence of these methods has still not been fully understood. First, the key concept of the methods, namely, the release of the accumulated stresses (or excessive elastic energy) in the source region of a forthcoming strong earthquake, is open to objection. If we treat an earthquake as a phenomenon of a loss in stability, then, the heterogeneities of the physicomechanical properties and stresses along the existing fault or its future trajectory, rather than the absolute values of stresses, play the most important role. In the present paper, this statement is illustrated by the classical examples of stable and unstable fractures and by the examples of the calculated stress fields, which were realized in the source regions of the tsunamigenic earthquakes of December 26, 2004 near the Sumatra Island and of September 29, 2009 near the Samoa Island. Here, just before the earthquakes, there were no excessive stresses in the source regions. Quite the opposite, the maximum shear stresses τ_max were close to their minimum value, compared to τ_max in the adjacent territory. In the present paper, we provide quantitative examples that falsify the theory of the prevention of PSE in its current form. It is shown that the measures for the prevention of PSE, even when successful for an already existing fault, can trigger or accelerate a catastrophic earthquake because of dynamic fault propagation in the intact region. Some additional aspects of prevention of PSE are discussed. We conclude that in the near future, it is too early to consider the problem of prevention of a forthcoming strong earthquake as a practical task; otherwise, the results can prove to be very different from the desired ones. Nevertheless, it makes sense to continue studying this problem. The theoretical research and experimental investigation of the structure and properties of the regions where the prevention of a forthcoming strong earthquake is planned in the future are of primary importance.     

Anisotropy of the apparent resistivity variation rate near the epicentral region for strong earthquakes

IntroductionThe geo-electrical anisotropy before earthquake is of special significance for the prediction of earthquake location and for the research on crustal stress status near the epicentral region. The anisotropy has been studied from various aspects (CHEN, et al, 1983; QIAN, et al, 1985, 1996; LU, et al, 1990a; MAO, et al, 1995; RUAN, et al, 1999). But the anisotropic phenomena presented by geo-electrical data are not practically satisfactory and not clear as compared with the res…     

Parameter estimation of the stochastic AMR model and its application to the study of several strong earthquakes

Introduction According to many published papers, seismicity in time-space domain shows some characteristics, such as doughnut epicenter distribution (Mogi, 1969) or quiescence of seismic activity before large earthquakes (WANG, et al, 2002), and aftershock decay (Ogata, 1998). In recent years, more and more seismologists (Lynnr, Steven, 1990) have found that many strong earthquakes are preceded by enhancing regional seismicity and accelerating strain energy release (ZHANG, et al, 2001). T…     

Is the abnormal response of the tide at the frequency of S2 really due to radiational effects?

The equilibrium ratios of the major solar component of the tide S₂ and of the component K₂, which have very close frequencies, seldom follow a linear trend when one extrapolates from that of the lunar component M₂. This is due to the different damping of the resultant of S₂ and K₂ during their six-month interference cycle, compared to that of the other components: it gives to K₂ a value larger than expected, while the reverse hold for S₂. It is unlikely that radiational effects are the cause of such behaviour as is currently believed.     

Performance of RC buildings after Kahramanmara? Earthquakes: lessons toward performance based design

Two simultaneous earthquakes occurred in the Kahramanmara?-Pazarc?k and Kahramanmara?-Elbistan districts of Turkey on February 6, 2023, and with magnitudes of 7.7 and 7.6, respectively. These events caused the highest estimated loss recorded in Turkey within the last century from natural disasters. The key reason for the extensive loss was the proximity of eleven cities to the earthquake epicenters. Middle East Technical University teams investigated the building sites in Gaziantep, Kahramanmara...     

The quiescence of earthquakes with M_L≥4.0 as an important precursory characteristic prior to strong shocks in North China region

Before a strong earthquake, there is often a process of quiescence or (absence( of regional seismic activity, which is a phenomenon that has attracted the attention of many scholars in China and other countries (LU, et al, 1985; Wesson, 1973). In the past ten-odd years, some Chinese seismologists made, earlier or later, special studies on the quiescence anomaly of seismicity in some specified areas from different angles. Taking the converted annual frequency of M=5.0 earthquakes in North Ch…     

Synchronization signals in the variations of groundwater chemical composition in Kamchatka in relation to the strong (M W ≥ 6.6) earthquakes

We consider the results of the statistical analysis using the methods of the principal components and canonical coherences applied to the processing of long (1986–2005) time series of hydrogeochemical observations at the flowing wells and springs in Kamchatka. The time-frequency diagrams of the evolution of informative statistics characterizing the collective behavior of multidimensional hydrogeochemical time series are constructed, and the time intervals and frequency bands where the synchronization signals (Lyubushin, 2007) appear are identified. The features of their occurrence are analyzed in comparison to the strong (M _w = 6.6?7.8) local earthquakes. It is found that such signals in the measurements of some multidimensional time series can arise both before and after earthquakes, i.e. these signals have a precursory (P2) and postseismic (P3) character.     

Is it possible to assess the ecological status of highly stressed natural estuarine environments using macroinvertebrates indices?

Several biotic indices have been proposed for the assessment of the ecological status of benthic macroinvertebrates in marine waters, although none have been generally accepted. When it comes to assessing highly stressed natural environments, such as estuaries, the controversy and uncertainty is much higher than for any given normal index. In this article, we test the behavior and suitability of different biotic indices proposed under the perspective of the Water Framework Directive (S, H, AMBI, M-AMBI, BQI, W-statistic, Taxonomic distinctness) for the assessment of estuaries in northern Spain. The low species richness and dominance of a few tolerant species in the characteristic community of these estuaries presented a challenge to the application of the biotic indices tested. Combined approaches that integrate different aspects of water quality and ecosystem functionality could increase the reliability of the ecological assessment of these transitional waters.     

Incorporating intensity bounds for assessing the seismic safety of structures: Does it matter?

The closed‐form solution for assessing the proportion of the mean annual frequency of limit‐state exceedance as a function of integration limits is introduced, in order to study whether or not the mean annual frequency of limit‐state exceedance is overestimated if the lower and(or) upper integration limit of the risk equation are(is) not selected in a physically consistent manner. Simple formulas for assessing the threshold value of the lower and upper integration limits are also derived. These formulas can be used to quickly assess the significant range of ground motion intensity that affects the mean annual frequency of limit‐state exceedance. It is shown that the threshold values of the integration limits depend on the median intensity causing a limit‐state, the corresponding dispersion and the slope of the hazard curve in the log domain. For several reinforced concrete buildings located in a region with moderate seismicity, it is demonstrated that the mean annual frequency of collapse can be significantly overestimated when assessed by integrating the risk equation over the entire range of ground motion intensity. Copyright © 2013 John Wiley & Sons, Ltd.     

Accelerating ground warming in the Canadian Prairie provinces: Is it a result of global warming?

The results of precision temperature logs made to depths of several hundred meters in some 80 wells in Western Canada, most of which are located in the Prairie Provinces, show evidence of warming at the ground surface in the 0.5 K to 3.5 K range (average=2.2±0.7 K, for 80 unevenly distributed sites). Modeling shows that this warming mostly pertains to this century and it has been most substantal in the last four decades if the ramp function of the linear increase of surface temperature is assumed. Using the step function model's increase of surface temperature (land clearing, forest fires, etc.) the calculated onset of warming would pertain mostly to the last two decades. Contour maps of ground temperatures currently and previously and a contour map of the ground warming magnitude dilineate a large regional character of the ground temperature change at the southern marigin of permafrost for the large area of the Prairie Provinces. In many cases however, the magnitude of ground warming is much larger than the magnitude of air warming. This is especially evident for the northern areas of Alberta in the boreal forest ecoprovince. The magnitude of ground warming is equal to the magnitude of surface air warming in southern Alberta in the grassland and aspen parkland ecoprovinces. The analysis of the temperature depth response to the surface warming from well data shows the integrated effect of surface air warming together with the increases in ground temperature due to natural terrain effects and other anthropogenical changes to the surface of the earth.     

The spatial temporal evolution characteristics of the load／unload response ratio（LURR） and its implications for predicting the three elements of earthquakes

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On the reality of the 56-year cycle and the increased probability of large earthquakes for Petropavlovsk-Kamchatskii during the period 2008–2011 according to lunar cyclicity

A 56-year cyclicity in the occurrence of large Kamchatka earthquakes has been previously detected. This is another manifestation of the tendency for the timing of large Kamchatka earthquakes to be synchronized to the cycles related to the period T _o of rotation of the lunar nodes found by V.A. Shirokov in 1974. He identified cycles of 18.6 years = T _o and 6.2 years = T _o/3, while the period of the 56-year cycle is 3T _o. The genuineness of that phenomenon had to be revised in connection with the occurrence of a large (M _w = 7.8) earthquake in Kamchatka at the end of 1997, in violation of the 56-year cyclicity. It turned out that, even though the 56-year cycle has become less distinct after the 1997 event, the cyclicity itself has remained statistically significant. A byproduct is an updated forecast of earthquake hazard for Kamchatka. The update is necessary in view of the approaching hazardous period of 2008–2011. It is found that, assuming the validity of these empirical tendencies, the expected rate of large earthquakes off Kamchatka for the period of August 2008 to October 2011 will be four times as high as the long-term mean. We derive the first-ever estimate of future hazard in terms of felt intensity for specified soil conditions (the so-called average soil) at a specified site (the town of Petropavlovsk-Kamchatskii). For these soil conditions, the estimated probability of at least one shock of intensity VII or greater during the period specified above is equal to 0.39 ± 0.15. The expected rate of single events or sets of events with M _w ≥ 7.6 in Kamchatka during this period is 0.76 ± 0.25.     

A class-oriented mechanical approach for seismic damage assessment of RC buildings subjected to the 2009 L’Aquila earthquake

The simplified mechanical method POST (PushOver on Shear Type models) for seismic vulnerability assessment of RC buildings is used in this study to derive damage scenarios for a database of 7597 RC buildings subjected to the 2009 L’Aquila earthquake. POST allows the evaluation of fragility curves through the determination of the non-linear static response of RC buildings in closed form, assuming the hypothesis of shear type behaviour, and considering the influence of infill panels both in the derivation of structural response and in assessment of building damage, which is defined according to the European Macroseismic Scale EMS-98. The aim of the present study is to provide a much more significant and reliable validation of the methodology, thanks to a much wider database compared to previous studies, and based on a different application of the methodology, i.e. at building class-level instead of single building-level. To this aim, the main geometrical-typological characteristics of the analysed buildings (number of storeys, age of construction, building area) have been statistically characterized based on data collected from post-earthquake AeDES survey forms, considering both the variability of each single parameter and the correlation that exists between one parameter and the other. This also allows to analyse the effectiveness of the adopted analytical procedure in predicting the general trends of observed damage with these parameters, showing a good agreement between observed and predicted trends. The overall predicted damage scenarios are compared with the corresponding observed ones, collected from AeDES survey forms, highlighting, again, a good agreement. Finally, the assumed mechanical interpretation of damage classification of EMS-98 is validated through the comparison between the distributions of damage to vertical structures and infill panels and the corresponding observed post-earthquake damage data.     

Numerical modeling of the impact of hurricanes on ocean dynamics: sensitivity of the Gulf Stream response to storm’s track

Ocean Dynamics - The study is focused on the disruption that a storm can cause to ocean stratification and ocean currents in a region dominated by a western boundary current and meso-scale...     

Trends in high flows in the central Spanish Pyrenees: response to climatic factors or to land-use change?

Abstract

This paper analyses the evolution of high flows in the central Spanish Pyrenees during the period 1955–1995. The method applied makes it possible to assess whether the contribution of the largest daily discharge and rainfall events to the total annual runoff and precipitation remains stationary or shows any temporal trend. The results show a general negative trend in flood intensity in the last decades, together with an increase in the importance of low flows in the total annual contribution. However, a change in the frequency distribution of precipitation events has not been detected. The different behaviour shown by runoff and precipitation could only be explained as being due to the increase in vegetation cover that is a consequence of the farmland abandonment and reforestation that occurred during the 20th century.     

Is correlation dimension a reliable proxy for the number of dominant influencing variables for modeling risk of arsenic contamination in groundwater?

The correlation dimension (CD) of a time series provides information on the number of dominant variables present in the evolution of the underlying system dynamics. In this study, we explore, using logistic regression (LR), possible physical connections between the CD and the mathematical modeling of risk of arsenic contamination in groundwater. Our database comprises a large-scale arsenic survey conducted in Bangladesh. Following the recommendation by Hossain and Sivakumar (Stoch Environ Res Risk Assess 20(1–2):66–76, 2006), who reported CD values ranging from 8 to 11 for this database, 11 variables are considered herein as indicators of the aquifer’s geochemical regime with potential influence on the arsenic concentration in groundwater. A total of 2,048 possible combinations of influencing variables are considered as candidate LR risk models to delineate the impact of the number of variables on the prediction accuracy of the model. We find that the uncertainty associated with prediction of wells as safe and unsafe by LR risk model declines systematically as the total number of influencing variables increases from 7 to 11. The sensitivity of the mean predictive performance also increases noticeably for this range. The consistent reduction in predictive uncertainty coupled with the increased sensitivity of the mean predictive behavior within the universal sample space exemplify the ability of CD to function as a proxy for the number of dominant influencing variables. Such a rapid proxy, based on non-linear dynamic concepts, appears to have considerable merit for application in current management strategies on arsenic contamination in developing countries, where both time and resources are very limited.