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In Geophysics, topographic factors are observations that can be directly measured, but they are often ignored to simplify the model. Studying the coseismic deformation caused by earthquakes helps accurately determine the epicenter's parameterization. It provides a reference for the reasonable layout of coseismic observation stations and GNSS observation stations. After the Mw7.8 earthquake in Nepal in 2015, GCMT, USGS, GFZ, CPPT, and other institutions released their epicenter parameter. However, according to their parameters, the coseismic displacements simulated by the spectral-element method are quite different from the GNSS observations. Firstly, this paper inverts the geometric parameters of the seismogenic fault with Nepal's coseismic GNSS displacement. The spectral-element method determines the source's location and depth under the heterogeneous terrain and outputs the source parameters. Among the results of many studies, the surface source is more consistent with the generation mechanism of large earthquakes. Secondly, this paper calculates the fault slip distribution of this earthquake using SDM (Steepest Descent Method) based on GNSS and InSAR data, which is divided into 1500 subfaults, and the moment tensor of each subfault is calculated. This paper investigates the distribution characteristics of the coseismic deformation field of the 2015 Mw 7.8 earthquake in Nepal under three different models. The results show that the influence of topographic factors is ~ 20%, and the influence of heterogeneous factors is ~ 10%. This paper concludes that the influence of topographic factors is much more significant than that of heterogeneous factors, and the influence of both should be addressed in coseismic deformation calculations. [ABSTRACT FROM AUTHOR]

Twenty papers on the study of tsunamis and respective tsunamigenic earthquakes are included in Volume II of the PAGEOPH topical issue 'Tsunami Science: Ten Years after the 2004 Indian Ocean Tsunami'. The papers presented in this second of two special volumes of Pure and Applied Geophysics reflect the state of tsunami science during this time, including five papers devoted to new findings specifically in the Indian Ocean. Two papers compile results from global observations and eight papers cover Pacific Ocean studies, focusing mainly on the 2011 Tohoku earthquake and tsunami. Remaining papers in this volume describe studies in the Atlantic Ocean and Mediterranean Sea and tsunami source studies. Overall, the volume not only addresses the pivotal 2004 Indian Ocean and 2011 Tohoku tsunamis, but also examines the tsunami hazard posed to other critical coasts in the world. [ABSTRACT FROM AUTHOR]

Two large earthquakes occurred in the western part of China in 2008, one of them being the Yutian (35.6°N, 81.6°E) M7.3 earthquake that occurred on March 21 (BJT) and the other the Wenchuan (31.0°N, 103.4°E) M8.0 earthquake that occurred on May 12 (BJT). In this paper, the West Continental China (included in 20.0°-50.0°N, 70.0°-110.0°E region) was the study region for verifyong the predictability of the pattern informatics (PI) method using the receiver-operating characteristic curve (ROC) test and R score test. Different forecasting maps with different calculating parameters were obtained. The calculating parameters were the grid size Δ x, base time t, reference interval t to t, change interval t to t, and forecasting interval t to t. In this paper, the base time t fixed to June 1, 1971, the ending forecast time t fixed to June 1, 2008, and the forecasting interval t to t changed from 1 to 10 years, and the grid sizes were chosen as 1° × 1° and 2° × 2°, respectively. The results show that the PI method could forecast the Yutian M7.3 and Wenchuan M8.0 earthquakes only using suitable parameters. Comparing the forecast results of grid sizes 1° × 1° and 2° × 2°, the models with 2° × 2° grids were better. Comparing the forecast results with different forecasting windows from 1 to 10 years, the models with forecasting windows of 4-8 years were better using the ROC test, and the models with forecasting windows of 7-10 years were better using the R score test. The forecast efficiency of the model with a grid size of 2° × 2° and forecast window of 8 years was the best one using either the ROC test or the R score test. [ABSTRACT FROM AUTHOR]

The evolution laws of LURR (Loading-Unloading Response Ratio) before strong earthquakes, especially the peak point of LURR, are described in this paper. The results of four methods (experimental, numerical simulation, seismic data analysis and with damage mechanics analysis) lead to a consistent conclusion-the evolution laws of LURR before strong earthquakes are that, at the early stage of the seismic cycle, LURR will fluctuate around 1 and in the late stage, it rises swiftly and to its peak point. At some time after this peak point, a catastrophic event or events occur. These do not occur at the peak point, but lag behind. The lag time which is denoted by T depends on the magnitude M of the upcoming earthquake among other factors. In order to consider the influence of geophysical parameters in a specific region such as $$ \dot{\gamma }, $$ E and J, where $$ \dot{\gamma } $$ is the shear strain rate of tectonic loading in situ, E is the sum of radiated energy of all earthquake occurring in a specific region measured during a long time duration (110 years in this paper) divided by the area of the region and the time duration, and J is a parameter denoting the LURR anomaly area weighted with Y (the value of LURR) and represents the expanse and degree of the seismogenic zone. The dimensional analysis method has been used to reveal the relation between M, T and other parameters in situ for more reliable earthquake prediction. [ABSTRACT FROM AUTHOR]

Resolving rupture processes of great earthquakes has fundamental importance to the study of earthquake physics, rupture dynamics, fault zone structure, and evolving processes. It also plays an essential role in earthquake hazard estimation, emergency response and seismic hazard mitigation. This paper reviews the major progress of the earthquake rupture process studies in the last decades, with an emphasize on the research directions of the department geophysics of Peking University including real-time response, back-projection techniques, geodetic data analysis, joint inversion and inversion in complex earth medium. We discussed the advantages and limitations of tradition methods; proposed a systematic and integrated approach from fast-response to detailed study. We also raised perspectives of using source models for ground motion prediction and the possibility of full-dynamic inversion. [ABSTRACT FROM AUTHOR]

The goal of the paper is to reveal the hierarchical block structure in the Tuan Giao area (Northwest Vietnam) and, on that base, to identify areas prone to earthquakes with M ≥ 5. Four large geoblocks of the second rank have been delineated on the basis of the joint analysis of geological, geophysical, geomorphic, and remote sensing data. The second rank geoblocks have been divided into smaller sub-blocks of the third rank. The recent geodynamics of the geoblocks have been characterized using geomorphic, seismological, gravity, and GPS data.The system of the delineated geoblocks is viewed as the Geodynamic Blocks model. The areas prone to earthquakes with M ≥ 5 have been identified using the pattern recognition algorithm CORA-3. The objects of the recognition were defined as circular areas, where boundaries of the geoblocks intersect each other. The recognition results confirm high seismic potential of the study region and provide information on potential earthquake sources for seismic hazard assessment: a number of boundary intersections have been identified as areas prone to earthquakes with M ≥ 5, where events of such magnitude have not been recorded up to date. Mordern geothermal activity and anomalies of dissolved methane (up to 10000 nL/L), helium and hydrogen in the hot mineral water springs prove high permeability of the study area and its active seismo-tectonic state. [ABSTRACT FROM AUTHOR]

The average relationship is established between the basic magnitude for the Kamchatka regional catalog, M , and modern moment magnitude M . The latter is firmly tied to the value of the source seismic moment M which has a direct physical meaning. M magnitude is not self-reliant but is obtained through the conversion of the traditional Fedotov's S-wave energy class, K . Installation of the digital seismographic network in Kamchatka in 2006-2010 permitted mass estimates of M and M to be obtained from the regional data. In this paper we outline a number of techniques to estimate M for the Kamchatka earthquakes using the waveforms of regional stations, and then compare the obtained M estimates with each other and with M , based on several hundred earthquakes that took place in 2010-2014. On the average, for M = 3.0-6.0, M = M -0.40; this relationship allows obtaining M estimates (proxy- M ) for a large part of the regional earthquake catalog with M = 3.4-6.4 ( M = 3.0-6.0). [ABSTRACT FROM AUTHOR]

The earthquake that struck Faial, Pico and São Jorge in 1998 has allowed the collection of an unprecedented quantity of good-quality data on damage to construction, costs of repair and other variables. A general overview of the impact of the earthquake is presented, and its effects on the population, housing, monumental structures and economy 10 years after its occurrence are analysed and briefly reported in this paper. We present the overall results obtained from multiple sources of information, primarily from an integrated database containing all the data gathered. The results that describe the inflicted damage, costs of repair and other variables are presented both statistically and geographically. This information was valuable for the construction of an overall earthquake impact based on the systemic analysis of the urban area through the identification of criteria and definition of descriptors leading to a disruption index. The paper is developed as follows. First, we introduce the descriptions of the earthquake effects on the broader set of existing urban systems. In the second part we present the main methodological aspects leading to the disruption index, as well as analysing and discussing the data to provide a clearer picture of how the analysed systems and their disruption affect an urban area. [ABSTRACT FROM AUTHOR]

Heavy tailed random variables (rvs) have proven to be an essential element in modeling a wide variety of natural and human-induced processes, and the sums of heavy tailed rvs represent a particularly important construction in such models. Oriented toward both geophysical and statistical audiences, this paper discusses the appearance of the Pareto law in seismology and addresses the problem of the statistical approximation for the sums of independent rvs with common Pareto distributionF(x)=1 -x-a for 1/2

- An algorithm recently developed by RUNDLEet al. (2002) to find regions of anomalous seismic activity associated with large earthquakes identified the location of anM w = 5.6 earthquake near Calexico, Mexico. In this paper we analyze the regional seismicity before this event, and a nearbyM w = 5.7 event, using time-to-failure algorithms developed by BOWMANet al. (1998) and BOWMAN and KING (2001a,b). The former finds the radius of a circular region surrounding the epicenter that optimizes the time-to-failure acceleration of seismic release. The latter optimizes acceleration based on the expected stress accumulation pattern for a dislocation source. Both methods found a period of accelerating seismicity in an optimal region, the size of which agrees with previously proposed scaling relations. This positive result suggests that the Rundle algorithm may provide a useful technique to identify regions of accelerating seismicity, which can then be analyzed using signal optimization time-to-failure techniques. [ABSTRACT FROM AUTHOR]

— The Indo-Burma (Myanmar) subduction boundary is highly oblique to the direction of relative velocity of the Indian tectonic plate with respect to the Eurasian plate. The area includes features of active subduction zones such as a Wadati-Benioff zone of earthquakes, a magmatic arc, thrust and fold belts. It also has features of oblique subduction such as: an arc-parallel strike-slip fault (Sagaing Fault) that takes up a large fraction of the northward component of motion and a buttress (the Mishmi block) that resists the motion of the fore-arc sliver. In this paper, I have examined the seismicity, slip vectors and principal axes of the focal mechanisms of the earthquakes to look for features of active subduction zones and for evidence of slip partitioning as observed in other subduction zones. The data set consists of Harvard CMT solutions of 89 earthquakes (1977–1999 with 4.8≦̸Mw≦̸7.2 and depths between 3–140 km). Most of these events are shallow and intermediate depth events occurring within the Indian plate subducting eastward beneath the Indo-Burman ranges. Some shallow events within the fore-arc region have arc-parallel Paxes, reflecting buttressing of the fore-arc sliver at its leading edge. Some of the shallowest events have nearly E-W oriented P axes which might account for recent folding and thrusting. Examination of earthquake slip vectors in this region shows that the slip vector azimuths of earthquakes in the region between 20°–26°N are rotated towards the trench normal, which is an indication of partial partitioning of the oblique convergence. It is seen that all aspects of seismicity, including the paucity of shallow underthrusting earthquakes and the orientation of P axes, are consistent with oblique convergence. The conclusions of this paper are consistent with recent geological studies and interpretations such as the coexistence of eastward subduction, volcanic activity and transcurrent movement through mid-Miocene to Quaternary period. [ABSTRACT FROM AUTHOR]

— The problem of the coseismic deformation induced by an earthquake on its own fault plane is investigated here. The analysis concentrates on the on-fault displacement field accompanying the occurrence of an earthquake in response to a prescribed uniform shear slip and it is carried out on the basis of the classical analytical model by Okada (1992) for a rectangular fault buried in an elastic homogeneous half-space delimited by a planar free surface. The analysis is subdivided into two separate papers: the first dealing with normal and the second with tangential on-fault displacements. In this first paper, concerning the study of the normal displacement component, the contributions of the source and of the correction introduced by the free surface are investigated separately and their dependence on the fault characteristics is thoroughly discussed. Particular attention is also devoted to the effects of the normal displacement on the fault surface geometry. It will be shown that the main effect is that of deforming the fault itself, with deformation consisting chiefly in a rotation of the plane and in a bending of the fault edges. The rotation angle is negligibly small (on the order of 1–10 μrad) for a single earthquake, although repeated seismic events occurring on the same fault might result in rotations of several degrees over geological time scales. [ABSTRACT FROM AUTHOR]

— This paper regards the on-fault displacement field generated by an earthquake on its own fault plane, with special attention to the tangential displacement vector. It is the continuation and the completion of a previous paper (Armigliato et al., 2003) concerning the analysis of the normal on-fault displacement component. It is here recognised that in addition to the discontinuous shear displacement, which is the main contribution to the seismic dislocation on the fault, there is a tangential displacement contribution that is continuous across the fault. The continuous tangential displacement is exclusively produced by the presence of the free earth's surface. The tangential displacement vector has non-vanishing components in both directions, parallel as well as perpendicular to the imposed uniform shear slip, the first being predominant on the second. We perform a set of computations aimed at evaluating the dependence of the tangential displacement magn itude on the relevant fault parameters for basic cases of rectangular faults embedded in a homogeneous half-space. [ABSTRACT FROM AUTHOR]

Crustal gravitational potential energy (GPE) change induced by earthquakes is an important subject in geophysics and seismology. For the past forty years the research on this subject stayed in the stage of qualitative estimate. In recent few years the 3D dynamic faulting theory provided a quantitative solution of this subject. The theory deduced a quantitative calculating formula for the crustal GPE change using the mathematic method of tensor analysis under the principal stresses system. This formula contains only the vertical principal stress, rupture area, slip, dip, and rake; it does not include the horizontal principal stresses. It is just involved in simple mathematical operations and does not hold complicated surface or volume integrals. Moreover, the hanging wall vertical moving (up or down) height has a very simple expression containing only slip, dip, and rake. The above results are significant to investigate crustal GPE change. Commonly, the vertical principal stress is related to the gravitational field, substituting the relationship between the vertical principal stress and gravitational force into the above formula yields an alternative formula of crustal GPE change. The alternative formula indicates that even with lack of in situ borehole measured stress data, scientists can still quantitatively calculate crustal GPE change. The 3D dynamic faulting theory can be used for research on continental fault earthquakes; it also can be applied to investigate subduction earthquakes between oceanic and continental plates. Subduction earthquakes hold three types: (a) crust only on the vertical up side of the rupture area; (b) crust and seawater both on the vertical up side of the rupture area; (c) crust only on the vertical up side of the partial rupture area, and crust and seawater both on the vertical up side of the remaining rupture area. For each type we provide its quantitative formula of the crustal GPE change. We also establish a simplified model (called CRW Model) as follows: for Type B and Type C subduction earthquakes, if the seawater average depth on the vertical up side of the rupture area is less than a tenth of the hypocenter depth, then take the approximation that the seawater above the continental plate is replaced by the upper crustal material of the continental plate. The formula of quantitative calculating the crustal GPE change is also provided for this model. Finally, for 16 September 2015 Mw 8.3 Illapel Chile earthquake, we apply CRW Model and obtain the following results: the crustal GPE change is equal to 1.8 × 10 J, and the hanging wall vertical moving-up height is 1.9 m with respect to the footwall. We believe this paper might be the first report on the quantitative solution of the crustal GPE change for this subduction earthquake; our results and related method will be helpful in research into the earthquakes in Peru-Chile subduction zone and the Andean orogeny. In short, this study expounds a new method for quantitative determining the crustal GPE change caused by subduction earthquakes, which is different from other existing methods. [ABSTRACT FROM AUTHOR]

The 16 September 2015 Illapel, Chile, earthquake and associated tsunami have been studied by many researchers from various aspects. This paper reviews studies on the source model of the earthquake and examines tsunami data. The Illapel earthquake occurred in the source region of previous earthquakes in 1943 and 1880. The earthquake source was studied using various geophysical data, such as near-field seismograms, teleseismic waveform and backprojection, GPS and InSAR data, and tsunami waveforms. Most seismological analyses show a duration of ~100 s with a peak at ~50 s. The spatial distribution has some variety, but they all have the largest slip varying from 5 to 16 m located at 31°S, 72°W, which is ~70 km NW of the epicenter. The shallow slip seems to be extended to the trench axis. A deeper slip patch was proposed from high-frequency seismic data. A tsunami earthquake model with a total duration of 250 s and a third asperity south of the epicenter is also proposed, but we show that the tsunami data do not support this model. [ABSTRACT FROM AUTHOR]

On Wednesday 6 April 1667, an earthquake occurred, and severely affected a large area of the eastern coast of the Adriatic Sea, also known as southern Dalmatia, in today Croatia, and part of Montenegro. This paper summarizes the seismological data existing today on this large earthquake, with special attention to how such data were gathered by means of investigating hitherto not considered historical sources of earthquake records. The obtained set of 37 macroseismic intensities in European Macroseismic Scale-EMS98 was processed, to obtain an epicentre located not far from the most damaged places, amongst them Ragusa (today Dubrovnik), and an Mw value of 6.4 ± 0.3. [ABSTRACT FROM AUTHOR]

To preserve the analog records of historical earthquakes which occurred in and around Iran in digital form and to make them available for modern analysis techniques that require waveforms, we decided to digitize seismograms of destructive earthquakes that occurred between 1960 and 1990. The seismograms have been recorded at five seismic stations deployed in Tehran, Mashhad, Kermanshah, Tabriz, and Shiraz by the Institute of Geophysics of the University of Tehran (IGUT). The restoration project of the old analog seismograms archived in the IGUT started in 2018. Seismograms were sorted by station and date to create a hardcopy databank, and then those from large earthquakes and their larger aftershocks were chosen for the scanning process. Seismograms of 52 significant earthquakes and their aftershocks with magnitudes greater than 5.0 that occurred in and around Iran were scanned. Besides that, seismograms of several significant and huge teleseismic earthquakes that occurred between 1960 and 1990 were scanned. At present, almost 600 scanned seismograms are available. The current digitization process in IGUT is done manually and is based on waveform vectorization. The provided databank is one of the most important sources of information for research in seismology and active tectonics in and around Iran. [ABSTRACT FROM AUTHOR]

In the frame of the European Commission project 'Seismic Hazard Harmonization in Europe' (SHARE), aiming at harmonizing seismic hazard at a European scale, the compilation of a homogeneous, European parametric earthquake catalogue was planned. The goal was to be achieved by considering the most updated historical dataset and assessing homogenous magnitudes, with support from several institutions. This paper describes the SHARE European Earthquake Catalogue (SHEEC), which covers the time window 1000-1899. It strongly relies on the experience of the European Commission project 'Network of Research Infrastructures for European Seismology' (NERIES), a module of which was dedicated to create the European 'Archive of Historical Earthquake Data' (AHEAD) and to establish methodologies to homogenously derive earthquake parameters from macroseismic data. AHEAD has supplied the final earthquake list, obtained after sorting duplications out and eliminating many fake events; in addition, it supplied the most updated historical dataset. Macroseismic data points (MDPs) provided by AHEAD have been processed with updated, repeatable procedures, regionally calibrated against a set of recent, instrumental earthquakes, to obtain earthquake parameters. From the same data, a set of epicentral intensity-to-magnitude relations has been derived, with the aim of providing another set of homogeneous Mw estimates. Then, a strategy focussed on maximizing the homogeneity of the final epicentral location and Mw, has been adopted. Special care has been devoted also to supply location and Mw uncertainty. The paper focuses on the procedure adopted for the compilation of SHEEC and briefly comments on the achieved results. [ABSTRACT FROM AUTHOR]

The western part of the Corinth Gulf attracts attention due to its seismically active fault system and considerable seismic hazard. A moderate size earthquake occurred close to the town of Efpalio on January 18, 2010, followed by a sequence of smaller earthquakes. In the present paper we use this sequence to derive a local structural model for the region in the vicinity of Efpalio. The model is based on the minimization of traveltime residuals. In particular, we used arrival times from 51 selected events recorded on January 19 and 20 by at least 5 stations at epicentral distances less than about 25 km. A variant of the method of conjugate gradients has been used for this purpose. In comparison with several previous models, the new model is characterized by higher velocities to a depth of about 8 km. The velocity ratio in the model is v / v = 1.83. The hypocentres of the selected earthquakes lay at depths between about 5 and 9 km, but their distribution is rather irregular. [ABSTRACT FROM AUTHOR]

The spring-block model proposed by Olami, Feder and Christensen (OFC) has several properties that are similar to those observed in real seismicity. In this paper we propose a modification of the original model in order to take into account that in a real fault there are several regions with different properties (non-homogeneity). We define regions in the network that is reminiscent of the real seismic fault, with different sizes and elastic parameter values. We obtain the Gutenberg-Richter law for the synthetic earthquake distributions of magnitude and the stair-shaped plots for the cumulative seismicity. Again, as in the OFC-homogeneous case, we obtain the stability for the cumulative seismicity stair-shaped graphs in the long-term situation; this means that the straight line slopes that are superior bounds of the staircases have a behavior akin to the homogeneous case. We show that with this non-homogeneous OFC model it is possible to include the asperity concept to describe high-stress zones in the fault. [ABSTRACT FROM AUTHOR]

The paper presents the results of a research study concerning the seismic response and design of r/c frames with overstrength discontinuities in elevation. The discontinuities are obtained assigning overstrengths either to the beams or to the columns of a 'regular frame' (assumed as reference). Two 'regular frames' are designed: one according to the Eurocode 8 (EC8) medium ductility class (DCM) rules and the other one according to the EC8 high ductility class (DCH) rules. For all frames the criteria of vertical strength irregularity of many international seismic codes are applied. Non linear static and dynamic analyses are performed; mechanical non linearity is concentrated at the element ends. These analyses are carried out according to EC8 provisions: for non linear static analysis the N2 method is applied; in the case of non linear time-history analyses, seven real earthquakes, selected in order to fit on average the elastic design spectrum, are used as input. The seismic response of frames characterised by the assigned overstrength is not very different with respect to the 'regular frame' one; furthermore all the frames satisfy the Ultimate Limit State, verified by the application of non linear static and dynamic analyses. This demonstrates that the sensitivity of frames, designed according to EC8 medium and high ductility classes, to overstrength vertical variations is low. Consequently, international code provisions on vertical strength regularity should be reviewed. [ABSTRACT FROM AUTHOR]

Although earthquakes are large idiosyncratic shocks for affected regions, little is known of their impact on economic activity. Seismic events are rare, the data are crude (the Richter scale measures the magnitude, but says nothing of the associated damages), and counterfactuals are often entirely absent. Using a geophysical methodology devised to gauge seismic damages (the so-called Mercalli scale), we study the evolution of output and employment following seismic events in 95 Italian provinces from 1986 to 2011 for a total of 22 earthquakes. Our identification strategy relies on ideal counterfactuals: ex ante identical neighboring provinces that only differ ex post in terms of damages. We show that following an earthquake, the observed contraction of output and employment is generally small or even negligible. In some cases, the net effect on output and employment can be positive because the stimulus from the reconstruction activities more than compensate for the destruction of physical capital. Finally, we show that the effects on economic activity are nonpersistent, do not spill over from the epicentral region to the neighbors, and tend to be reabsorbed within 2 years from the event. [ABSTRACT FROM AUTHOR]

This paper discusses the prospects of application of the laser deformographs, broadband seismographs, and GPS/GLONASS receivers for the purpose of prediction of a probable crustal earthquake with magnitude 7 at the depth of 20 km by variations of the stress-strain field of the Earth on its surface. The measurement carried out have shown that the application of laser deformographs can solve this problem, while the application of various seismographs and GPS/GLONASS receivers cannot help to do this. [ABSTRACT FROM AUTHOR]

Izmir, the third largest city and one of the major economic centers in Turkey, has more than three million residents and one-half million buildings. The city, located in a seismically active region in western Anatolia, was a subject of the 1997 RADIUS (Risk Assessment Tools for Diagnosis of Urban Areas against Seismic Disaster) project. In this paper, the seismic hazard of Izmir is investigated through probabilistic seismic hazard assessment. First, the seismic setting of Izmir is presented. Considering the statistics of earthquakes that took place in the region during the period 1900-2005, a simple seismic hazard model is used to facilitate the assessment. To account for modeling uncertainties associated with the values of seismicity parameters, a logic tree procedure is employed in carrying out the seismic hazard computations. The resulting weighted average seismic hazard, presented in terms of peak ground acceleration and associated probability of exceedence, could be considered the 'best estimate' of seismic hazard for Izmir. Accordingly, for a return period of 475 years, for rock sites, a PGA value of 0.34 g is calculated. This PGA hazard estimate is close to the current code-recommended design acceleration level for Izmir. [ABSTRACT FROM AUTHOR]

In this paper, ground motion during the Independence Day earthquake of August 15, 1950 (Mw 8.6, B en-M enahem et al., 1974) in the northeastern part of India is estimated by seismological approaches. A hybrid simulation technique which combines the low frequency ground motion simulated from an analytical source mechanism model with the stochastically simulated high-frequency components is used for obtaining the acceleration time histories. A series of ground motion simulations are carried out to estimate the peak ground acceleration (PGA) and spectral accelerations at important cities and towns in the epicentral region. One sample PGA distribution in the epicentral region encompassing the epicenter is also obtained. It is found that PGA in the epicentral region has exceeded 1 g during this earthquake. The estimated PGA’s are validated to the extent possible using the MMI values. The simulated acceleration time histories can be used for the assessment of important engineering structures in northeastern India. [ABSTRACT FROM AUTHOR]

The article presents a list of published papers authored or co-authored by geophysicist Keiiti Aki. Periodical articles the list include "Quantitative prediction of earthquake occurrence as stochastic phenomena," "Thermal processes near the earth's crust," "Relay computer for correlogram analysis," and "Correlogram analysis of seismograms."

— The study of surface deformation due to seismic activity is often made using dislocations with uniform slip and simple geometries. A better modeling of coseismic and postseismic surface displacements can be obtained by using dislocations with variable slip and nonregular shapes. This is consistent with the asperity model of fault surfaces, assuming a friction distribution on faults made of locked zones with much higher friction than surrounding zones. In this paper we consider the 1997–1998 Colfiorito seismic sequence. The coseismic surface displacements in the Colfiorito zone are used in order to infer the slip distribution on the fault surface at different stages of the sequence. The displacement field has been modeled varying the slip distribution on the fault, and comparing the deformation observed by SAR and GPS techniques with model results. The slip distribution is calculated by Monte Carlo simulations on a normal fault with the dip angle equal to 40°. A good approximation is obtained by using square asperity units of 1.5×1.5 km2. In the first stage, we employed a simplified model with uniform slip, in which each asperity unit is allowed to slip a constant amount or not to slip at all, and in the second stage, we evaluate the slip distribution in the dislocation area determined by the Monte Carlo inversion: in this case we allow unit cells to undergo different values of slip in order to refine the initial dislocation model. The results show that the 1997 seismic events of the sequence can be modeled by irregular dislocations, obtaining a good fit to the DInSAR and GPS observations. The model also confirms the results of previous studies by a different methodology, defining the distribution of asperities on the fault plane using the fault geometry, the geodetic data and the seismic moment of the 1997–1998 Colfiorito seismic sequence. Furthermore, the analysis of 1997 aftershocks in the seismogenic region shows a strong correlation between most events and the asperity distribution, which can be considered as an independent test of the validity of the model. [ABSTRACT FROM AUTHOR]

— An overview of the most important developments in Engineering (or Strong Motion) Seismology is presented alongside Professor Keiiti Aki's contributions, who is one of the founders of this field. The mechanics of earthquake rupture are discussed with due emphasis on the various physical phenomena. The presentation is made in a tutorial manner, borrowing freely from Keiiti Aki's papers, and endeavoring to emulate his unique style of clarity, simplicity and synthetic ability. [ABSTRACT FROM AUTHOR]

Deep-focus earthquakes that occur at 350–660 km are assumed to be caused by olivine → spinel phase transformation (PT). However, there are many existing puzzles: (a) What are the mechanisms for jump from geological 10−17 − 10−15 s−1 to seismic 10 − 103 s−1 strain rates? Is it possible without PT? (b) How does metastable olivine, which does not completely transform to spinel for over a million years, suddenly transform during seconds? (c) How to connect shear-dominated seismic signals with volume-change-dominated PT strain? Here, we introduce a combination of several novel concepts that resolve the above puzzles quantitatively. We treat the transformation in olivine like plastic strain-induced (instead of pressure/stress-induced) and find an analytical 3D solution for coupled deformation-transformation-heating in a shear band. This solution predicts conditions for severe (singular) transformation-induced plasticity (TRIP) and self-blown-up deformation-transformation-heating process due to positive thermomechanochemical feedback between TRIP and strain-induced transformation. This process leads to temperature in a band, above which the self-blown-up shear-heating process in the shear band occurs after finishing the PT. Our findings change the main concepts in studying the initiation of the deep-focus earthquakes and PTs during plastic flow in geophysics in general. The developed theory for coupled deformation, plastic strain-induced phase transformation, transformation-induced plasticity, and self-blown-up deformation-transformation-heating in shear band explains the main puzzles of deep-focus earthquakes. [ABSTRACT FROM AUTHOR]

Sivas city, located in the inner east part of Anatolia (Turkey), is far from seismic sources. However, the city is under risk owing to strong earthquakes occurring around the area, and different soil conditions that can produce variation in the ground motion amplification. Microzonation of cities provides a basis for site-specific hazard analysis in urban settlements. In particular, seismic microzonation can be achieved by means of detailed seismic assessment of the area, including earthquake recordings and geological studies. In this paper, we propose a preliminary microzonation map for the city of Sivas, based on the variation in the dominant periods of the sediments covering the area. The periods are retrieved from microtremor measurements conducted at 114 sites, using the horizontal-to-vertical spectral ratio technique. The results of microtremor analysis were compared with those obtained from refraction microtremor measurements at two profiles crossing the studied area. According to the classification of dominant periods, Sivas area can be divided into four zones, probably prone to different levels of seismic hazard. However, specific studies including analysis of weak earthquakes are required in the future to validate our microzonation map. [ABSTRACT FROM AUTHOR]

The inclusion of fragment-asperity interaction inside tectonic plates to find a frequency magnitude relation for earthquakes, and the need for non-extensive statistics in this case is exposed. The usefulness of this formulation is shown. A comparison with seismic observations is also discussed. [ABSTRACT FROM AUTHOR]

It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of ∼600 °C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle–ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting. [ABSTRACT FROM AUTHOR]

Geophysicist Frank Press was director of Caltech’s Seismological Laboratory from 1957 to 1965. In this interview, he recalls his work with Maurice Ewing at Columbia’s Lamont Geological Observatory; his directorship of Caltech’s Seismological Laboratory and colleagues Charles Richter, Beno Gutenberg, and Hugo Benioff; his work on the free oscillations of the earth; and his part in establishing the worldwide network of seismographs for the detection of nuclear weapons testing. [ABSTRACT FROM AUTHOR]

The 29 May 2017 Mw 6.6 Poso earthquake occurred in the eastern part of Central Sulawesi with a normal faulting mechanism, which is the largest normal earthquake to have occurred in the region since instrumental records have been available. Approximately 400 aftershocks were well-recorded by the Indonesian Agency for Meteorology, Climatology, and Geophysics' (BMKG) broadband seismic network for 1 month after the mainshock. Here, we obtain the source parameters of the Mw 6.6 mainshock by using moment tensor inversion on seismic data that came from 14 stations within a radius of 7° from the mainshock epicenter. It results in the best point-source solution of 103°, 56°, and −100° for the strike, dip, and rake, respectively, and a centroid depth of 6.4 km. The kinematic solution shows a unilateral rupture process with an average slip of ~ 0.5 m on a 20-km rupture length. The source mechanism indicates the extension behavior in the eastern part of Central Sulawesi and the northward mass extrusion process that occurred in the area during the Quaternary. Based on the seismic source parameters and geomorphologic analysis, we propose the Tokorondo Fault as being responsible for the earthquake. A total of 361 aftershock hypocenters are successfully relocated using the double-difference method and indicate three clusters of the off-fault aftershocks. We calculate the Coulomb failure stress (CFS) changes to investigate the occurrence of these aftershocks. The result indicates that the off-fault aftershocks have mostly occurred within the increased CFS change area with a value > 0.1 bar. [ABSTRACT FROM AUTHOR]

Delhi region in northern India experiences frequent shaking due to both far-field and near-field earthquakes from the Himalayan and local sources, respectively. The recent M3.5 and M3.4 earthquakes of 12th April 2020 and 10th May 2020 respectively in northeast Delhi and M4.4 earthquake of 29th May 2020 near Rohtak (~ 50 km west of Delhi), followed by more than a dozen aftershocks, created panic in this densely populated habitat. The past seismic history and the current activity emphasize the need to revisit the subsurface structural setting and its association with the seismicity of the region. Fault plane solutions are determined using data collected from a dense network in Delhi region. The strain energy released in the last two decades is also estimated to understand the subsurface structural environment. Based on fault plane solutions, together with information obtained from strain energy estimates and the available geophysical and geological studies, it is inferred that the Delhi region is sitting on two contrasting structural environments: reverse faulting in the west and normal faulting in the east, separated by the NE-SW trending Delhi Hardwar Ridge/Mahendragarh-Dehradun Fault (DHR-MDF). The WNW-ESE trending Delhi Sargoda Ridge (DSR), which intersects DHR-MDF in the west, is inferred as a thrust fault. The transfer of stress from the interaction zone of DHR-MDF and DSR to nearby smaller faults could further contribute to the scattered shallow seismicity in Delhi region. [ABSTRACT FROM AUTHOR]

Asperity models for ground motion prediction is widely used in Japan. Here we expand the application of these asperity models to predict fault displacement caused by surface rupture. The proposed approach is rather simple and practical for the use in fault displacement hazard analysis in nuclear installations and other critical infrastructures, as it is the emphasis of the current topical issue. The proposed method mainly consists of two steps. The first step consists in the characterization of asperities at the seismogenic zone based on the kinematic asperity source model following Irikura's recipe (Irikura and Miyake in Pure Applied Geophysics, 168:85–104, 2011) for strong ground motion prediction. Since the kinematic model does not take into account surface rupture mechanism, this first step assumes that the fault is buried, and then by trial and error procedure the stress drop on the asperities are estimated, so that the average slip at each asperity be consistent with the ones from the kinematic model. At this stage, the dynamic model predicts strong ground motion consistent with those from the kinematic model. In the second step, the surface rupture is included by calibrating the shallow layer (SL) with stress drop, strength excess and critical slip distance, so that the final fault displacement along the fault be consistent with observations. The 2010 Mw 7.0 Darfield (New Zealand) earthquake is used to test the proposed method. Surface-rupturing was observed in several sites along the main fault reaching values of fault displacement larger than 5 m. The main fault of this earthquake is strike-slip, almost vertical. Therefore, a simplified planar fault asperity model to capture the main features of the fault displacement is assumed. The fault dimensions are assumed to have a length of 60 km and a width of 24 km with three asperities. The preferred model of the first step predicts average slip for each asperity of 2.7, 2.7, and 2 m corresponding, respectively, to stress drops of 6.0 MPa, 8.5 MPa, and 7.0 MPa. In the second step, the surface rupture is calibrated assuming a SL zone of 3 km depth. We found that negative stress drop is not necessary in the SL, because this strongly inhibits surface rupturing. Our preferred model produces fault displacement distribution closer to the observed ones, but average slip at each asperity increases to 3.4 m, 3.2 and 2.8 m. This increase in average slip is due to the contribution of surface rupturing. Ground motion differences between fault-surface rupturing and buried models are negligible, except at the very near-source. These differences are attributed to the SL rupture that mainly affect the ground motion at the very near-source. Overall, our simple asperity model captures the main features of the observed fault displacement and near-source ground motion, proving that the proposed simple and practical two step-procedure provides meaningful estimate of fault displacement and near-source ground motion consistent with observations, as such, this method has the potential to be used in practical fault displacement hazard analysis. [ABSTRACT FROM AUTHOR]

The historical and the present seismicity catalogues of the Garhwal Himalaya have been studied for their spatio-temporal variations and their implications on the seismotectonics of the region. The Micro-Seismicity, Fractal dimensions (Dc) and Frequency Magnitude Distribution (b-value) coupled with the available literature on geology, geomorphology and geophysics have been used to derive the seismotectonics and stress level changes in the region. The seismic cross sections for the relocated micro-seismicity, focal mechanisms and the swath profiles (for the presence of Physiographic Transition 2 (PT2) at the foothill of the Higher Himalaya) indicate the constant presence of the Mid-Crustal Ramp (MCR) in the detachment plane and its active seismogenic nature. The comparison of this scenario suggests the constant presence of seismogenically active MCR structure throughout the Central Seismic Gap. The seismic cross sections further reveal that the sensu stricto Main Central Thrust (Munsiari Thrust) is also a site of generation of the micro-seismicity in few segments due to its reactivation by thrusting along the MCR. The high fractal dimension value (Dc = 1.47) suggests the heterogeneous nature of the region, owing to the presence of local faults and transverse tectonics. The high stress accumulation in the Garhwal Himalaya with low b value (b = 0.70) suggests the high probability of occurrence of a larger or greater earthquake in the near-future. Further, the study also reveals that the 2011 Chamoli earthquake of M 5.0, preceded by a quiescence period of nearly a year shows different stress levels before and after its occurrence, which is well constrained with the increased moderate earthquake activity around the Chamoli region. This increased seismic activity and stress conditions in the Chamoli region suggest the high possibility of the occurrence of major earthquakes, hence the study recommend for a detailed seismic hazard evaluation of the region. [ABSTRACT FROM AUTHOR]

The Earthquake Model of Middle East (EMME) project was carried out between 2010 and 2014 to provide a harmonized seismic hazard assessment without country border limitations. The result covers eleven countries: Afghanistan, Armenia, Azerbaijan, Cyprus, Georgia, Iran, Jordan, Lebanon, Pakistan, Syria and Turkey, which span one of the seismically most active regions on Earth in response to complex interactions between four major tectonic plates i.e. Africa, Arabia, India and Eurasia. Destructive earthquakes with great loss of life and property are frequent within this region, as exemplified by the recent events of Izmit (Turkey, 1999), Bam (Iran, 2003), Kashmir (Pakistan, 2005), Van (Turkey, 2011), and Hindu Kush (Afghanistan, 2015). We summarize multidisciplinary data (seismicity, geology, and tectonics) compiled and used to characterize the spatial and temporal distribution of earthquakes over the investigated region. We describe the development process of the model including the delineation of seismogenic sources and the description of methods and parameters of earthquake recurrence models, all representing the current state of knowledge and practice in seismic hazard assessment. The resulting seismogenic source model includes seismic sources defined by geological evidence and active tectonic findings correlated with measured seismicity patterns. A total of 234 area sources fully cross-border-harmonized are combined with 778 seismically active faults along with background-smoothed seismicity. Recorded seismicity (both historical and instrumental) provides the input to estimate rates of earthquakes for area sources and background seismicity while geologic slip-rates are used to characterize fault-specific earthquake recurrences. Ultimately, alternative models of intrinsic uncertainties of data, procedures and models are considered when used for calculation of the seismic hazard. At variance to previous models of the EMME region, we provide a homogeneous seismic source model representing a consistent basis for the next generation of seismic hazard models within the region. [ABSTRACT FROM AUTHOR]

Strong-motion records of recent Gorkha Nepal earthquake ( M 7.8), its strong aftershocks and seismic events of Hindu kush region have been analysed for estimation of source parameters. The M 7.8 Gorkha Nepal earthquake of 25 April 2015 and its six aftershocks of magnitude range 5.3-7.3 are recorded at Multi-Parametric Geophysical Observatory, Ghuttu, Garhwal Himalaya (India) >600 km west from the epicentre of main shock of Gorkha earthquake. The acceleration data of eight earthquakes occurred in the Hindu kush region also recorded at this observatory which is located >1000 km east from the epicentre of M 7.5 Hindu kush earthquake on 26 October 2015. The shear wave spectra of acceleration record are corrected for the possible effects of anelastic attenuation at both source and recording site as well as for site amplification. The strong-motion data of six local earthquakes are used to estimate the site amplification and the shear wave quality factor ( Q ) at recording site. The frequency-dependent Q ( f) = 124 f is computed at Ghuttu station by using inversion technique. The corrected spectrum is compared with theoretical spectrum obtained from Brune's circular model for the horizontal components using grid search algorithm. Computed seismic moment, stress drop and source radius of the earthquakes used in this work range 8.20 × 10-5.72 × 10 Nm, 7.1-50.6 bars and 3.55-36.70 km, respectively. The results match with the available values obtained by other agencies. [ABSTRACT FROM AUTHOR]

We study relaxation patterns of violent conflicts after bursts of activity. Data were obtained from available catalogs on the conflicts in Iraq, Afghanistan and Northern Ireland. We find several examples in each catalog for which the observed relaxation curves can be well described by an asymptotic power-law decay (the analog of the Omori's law in geophysics). The power-law exponents are robust, nearly independent of the conflict. We also discuss the exogenous or endogenous nature of the shocks. Our results suggest that violent conflicts share with earthquakes and other natural and social phenomena a common feature in the dynamics of aftershocks. [ABSTRACT FROM AUTHOR]

A preface to the January 1, 2013 issue of the journal "Pure & Applied Geophysics," is presented.

The earthquake of 21 May 2014 (Mw 6.0) in the northern Bay of Bengal (BOB) highlights the importance of studies on intraplate earthquakes in the oceanic regime for understanding the stress state of the oceanic lithosphere. The epicenter of the earthquake is located at a water depth of 2.5 km where the sediment thickness is nearly 12 km, and it occurs at a depth of ~50 km within the upper mantle. Its location on the seismotectonic map of the region shows that the epicenter is far from the seismically active zone of the Burmese Arc in the east and low-to-moderately active seismic region of the east coast of India in the west. The fault plane solution of this earthquake indicates that it was a strike-slip event with a right-lateral sense of motion on a NW-oriented nodal plane, and it occurred on one of the NW-SE-trending fracture zones previously mapped in the BOB. Based on a compilation of long-term (1900-2011) intraplate earthquakes along with available focal mechanisms in the BOB and the adjoining east coast of India, we conclude the following: (1) the Precambrian structural trends, basin-scale faults and minor lineaments on the east coast of India are favorably reactivated in their offshore extensions up to the shelf-slope areas of the margin; (2) earthquake occurrences in the BOB region can be correlated with the fracture zone trends in the central BOB and along the Ninetyeast ridge or at the intersections of fracture zones with the subsurface trace of the 85°E ridge. The 21 May 2014 earthquake is the result of reactivation of such a NW-SE-trending fracture zone lying in the lithosphere of >100 Ma in age. Further evaluation of this event in light of the global occurrence of oceanic intraplate earthquakes in the older lithosphere (>80 Ma) suggests that such reactivation is possible in the high ambient stress state. [ABSTRACT FROM AUTHOR]

We present a systematic and updated overview of a seismotectonic model for the Po Plain (northern Italy). This flat and apparently quiet tectonic domain is, in fact, rather active as it comprises the shortened foreland and foredeep of both the Southern Alps and the Northern Apennines. Assessing its seismic hazard is crucial due to the concentration of population, industrial activities, and critical infrastructures, but it is also complicated because (a) the region is geologically very diverse, and (b) nearly all potential seismogenic faults are buried beneath a thick blanket of Pliocene-Pleistocene sediments, and thus can be investigated only indirectly. Identifying and parameterizing the potential seismogenic faults of the Po Plain requires proper consideration of their depth, geometry, kinematics, earthquake potential and location with respect to the two confronting orogens. To this end, we subdivided them into four main, homogeneous groups. Over the past 15 years we developed new strategies for coping with this diversity, resorting to different data and modeling approaches as required by each individual fault group. The most significant faults occur beneath the thrust fronts of the Ferrara-Romagna and Emilia arcs, which correspond to the most advanced and buried portions of the Northern Apennines and were the locus of the destructive May 2012 earthquake sequence. The largest known Po Plain earthquake, however, occurred on an elusive reactivated fault cutting the Alpine foreland south of Verona. Significant earthquakes are expected to be generated also by a set of transverse structures segmenting the thrust system, and by the deeper ramps of the Apennines thrusts. The new dataset is intended to be included in the next version of the Database of Individual Seismogenic Sources (DISS; , version 3.2.0, developed and maintained by INGV) to improve completeness of potential sources for seismic hazard assessment. [ABSTRACT FROM AUTHOR]

The negative binomial distribution is presented as the waiting time distribution of a cyclic Markov model. This cycle simulates the seismic cycle in a fault. As an example, this model, which can describe recurrences with aperiodicities between 0 and 0.5, is used to fit the Parkfield, California earthquake series in the San Andreas Fault. The performance of the model in the forecasting is expressed in terms of error diagrams and compared with other recurrence models from literature. [ABSTRACT FROM AUTHOR]

Here, we describe an original geophysical multi-method approach applied to the Mount Marzano Fault System. This is one of the most hazardous seismogenic faults of the Apennines (Irpinia, southern Italy), and it was responsible for the 1980, Mw 6.9, earthquake, along with many others before. We carried out electrical resistivity tomography (ERT), ground penetrating radar (GPR) measurements, and horizontal-to-vertical spectral ratio (HVSR) microtremor analysis along several common transects designed across the potential and/or certain fault traces. The data obtained from these non-invasive, inexpensive, expeditious methods mutually integrate with and complement each other, providing a valuable subsurface image of the near surface fault architecture. ERT depicts the general shallow image of the fault zone and of the fault-controlled sedimentary basin, with the depth of the buried bedrock cross-correlated through ambient-noise HVSR results. GPR delineates the very shallow geometry of the fault and of the associated deformation. Coupled with previous paleoseismological studies, these data allow the evaluation of some fault parameters and the precise locating of the fault trace, to aid future paleoseismological investigations aimed at seismic risk reduction programs. [ABSTRACT FROM AUTHOR]

The article desribes a topological approach to the theory of prognosis of seismicity based on a mechanical conception. It describes the topological approach in the thery of block structures in the presence of block elements of various dimensions. It notes on the pseudodifferential equation used to represent the black boundary.

Basing on the Asymmetric Continuum Theory, we develop the thermodynamics including fragmentation spin fracture processes; applications for the earthquake source processes are considered. The fracture band model is used to describe a dislocation and disclination superlattice. The Gibbs free energy of defect formation is specified. A dynamic spin fracture criterion was formulated. Consequently, a dynamic model of rock fracture employing dislocations, disclinations, and cracks was constructed to describe slip and fragmentation fracture processes in the earthquake sources. [ABSTRACT FROM AUTHOR]

The effect of location errors in the performance of seismicity-based forecasting methods was studied here using one particular binary forecast technique, the Pattern Informatics (PI) technique (R undle et al., Proc Nat Acad Sci USA 99, 2514-2521, ; T iampo et al., Pure Appl Geophys 159, 2429-2467, ). The Southern Californian dataset was used to generate a series of perturbed catalogs by adding different levels of noise to epicenter locations. The PI technique was applied to these perturbed datasets to perform retrospective forecasts that were evaluated by means of skill scores, commonly used in atmospheric sciences. These results were then compared to the effectiveness obtained from the original dataset. Isolated instances of decline of the PI performance were observed due to the nature of the skill scores themselves, but no clear trend of degradation was identified. Dependence on the total number of events in a catalog also was studied, with no systematic degradation in the performance of the PI for catalogs with events in the cases studied. These results suggest that the stability of the PI method is due to the invariance of the clustering patterns identified by the TM metric (T hirumalai and M ountain, Phys Rev A 39, 3563-3573, 1989) when applied to seismicity. [ABSTRACT FROM AUTHOR]

Observed high-frequency (HF) radiation from earthquake faults exhibits specific properties that cannot be deduced or extrapolated from low-frequency fault behavior. In particular: (1) HF time functions look like random signals, with smooth mean spectrum and moderately heavy-tailed probability distribution function for amplitudes; (2) well-known directivity of low-frequency radiation related to rupture propagation is strongly reduced at HF, suggesting incoherent (delta-correlated) behavior of the HF radiator, and contradicting the usual picture of a rupture front as a regular, non-fractal moving line; (3) in the spectral domain, HF radiation occupies a certain specific band seen as a plateau on acceleration source spectra $$ K(f) = f^{2} \dot{M}_{0} (f) $$. The lower cutoff frequency f of K(f) spectra is often located significantly higher than the common spectral corner frequency f, or f. In many cases, empirical f( M) trends are significantly slower as compared to the simple f ∝ M, testifying the lack of similarity in spectral shapes; (4) evidence is accumulating in support of the reality of the upper cutoff frequency of K(f): fault-controlled f, or f. However, its identification is often hampered by such problems as: (a) strong interference between f and site-controlled f; (b) possible location of f above the observable spectral range; and (c) substantial deviations of individual source spectra from the ideal spectral shape; (5) intrinsic structure of random-like HF radiation has been shown to bear significant self-similar (fractal) features. A HF signal can be represented as a product of a random HF 'carrier signal' with constant mean square amplitude, and a positive modulation function, again random, that represents a signal envelope. It is this modulation function that shows approximately fractal behavior. This kind of behavior was revealed over a broad range of time scales, from 1 to 300 s from teleseismic data and from 0.04 to 30 s from near-fault accelerogram data. To explain in a qualitative way many of these features, it is proposed that rupture propagation can be visualized as occurring, simultaneously, at two different space-time scales. At a macro-scale (i.e. at a low resolution view), one can safely believe in the reality of a singly connected rupture with a front as a smooth line, like a crack tip, that propagates in a locally unilateral way. At a micro-scale, the rupture front is tortuous and disjoint, and can be visualized as a multiply connected fractal 'line' or polyline. It propagates, locally, in random directions, and is governed by stochastic regularities, including fractal time structure. The two scales and styles are separated by a certain characteristic time, of the order of (0.07-0.15) × rupture duration. The domain of fractal behavior spans a certain HF frequency range; its boundaries, related to the lower and upper fractal limits, are believed to be manifested as f and f. [ABSTRACT FROM AUTHOR]

A large number of earthquake studies using both empirical and theoretical approaches clearly depict the strong correlation of resulting damage and local geology. This correlation forms the scientific basis of the subsurface soil structure studies for site response evaluation, since adequate knowledge of the subsoil geotechnical and geophysical properties can lead to realistic seismic hazard estimation through appropriate modeling of strong seismic motion. In this framework, ambient noise analysis and one dimensional numerical simulation modeling have been performed for the town of Grevena (Northwestern Greece) in order to study both the subsurface soil structure, as well as its expected effect on seismic motions. The horizontal to vertical spectral ratio (HVSR) method was implemented on an almost uniform grid of 60 single station ambient noise measurements inside the urban area, while the noise array technique was applied at four selected sites of the study area. The HVSR curves show complex patterns, occasionally with double HVSR peak frequencies, with the higher one HVSR frequency showing a good correlation with the recent Holocene clay-dominant formation. Using these results, as well as information on surface geology and existing geotechnical data, a microzonation of the Grevena town is attempted, indicating zones of similar site response to ground motion. Numerical simulation of ambient noise with synthetic recordings suggests that the complex features observed in several HVSR curves could be attributed to the impedance contrast due to the quite shallow (Holocene clays to Pliocene-Pleistocene sands) and a deeper (Pliocene-Pleistocene sands to Oligocene-Miocene bedrock) sedimentary formation. [ABSTRACT FROM AUTHOR]