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The paper presents historical perspective of fibre-optic seismographs designed and constructed at the Institute of Applied Physics at Military University of Technology, Poland based on the so-called minimum configuration of fibre-optic gyroscope. The briefly presented history, which originated in the 1998 by the system named GS-13P, laid solid foundations for the construction of a three-axis fibre-optic seismograph. The presented system meets all technical requirements of rotational seismology in terms of measurement parameters (measuring range from 10−8 rad/s to several rad/s and frequency from 0.01 Hz to 100 Hz) and utility features (mobility, autonomy, power independence, environmental stability). The presented device provides universal application both for research in engineering applications (high buildings, chimneys, wind towers) as well as in seismological research. [ABSTRACT FROM AUTHOR]

The 2017 Mw 7.3 Iran-Iraq earthquake occurred in a region where the pattern of major plate convergence is well constrained, but limited information is available on the seismogenic structures. Geological observations, interpretation of seismic reflection profiles, and well data are used in this paper to build a regional, balanced cross section that provides a comprehensive picture of the geometry and dimensional parameters of active faults in the hypocentral area. Our results indicate (i) the coexistence of thin- and thickskinned thrusting, (ii) the reactivation of inherited structures, and (iii) the occurrence of weak units promoting heterogeneous deformation within the palaeo-Cenozoic sedimentary cover and partial decoupling from the underlying basement. According to our study, the main shock of the November 2017 seismic sequence is located within the basement, along the low-angle Mountain Front Fault. Aftershocks unzipped the up-dip portion of the same fault. This merges with a detachment level located at the base of the Paleozoic succession, to form a crustal-scale fault-bend anticline. Size and geometry of the Mountain Front Fault are consistent with a down-dip rupture width of 30 km, which is required for an Mw 7.3 earthquake. [ABSTRACT FROM AUTHOR]

Using a three-dimensional (3D) seismic reflection dataset from the Shipwreck Trough, offshore Otway Basin, southern Australia, we aim to characterise and understand the structural evolution of the Shipwreck Fault Zone (SFZ) and associated extensional structures. The SFZ is a key structural element of the Otway Basin, which is a NW striking, Upper Jurassic-Cenozoic, rift-to-passive margin basin that formed due to the breakup of Australia and Antarctica. The SFZ marks the transition from the major southern margin rift system to the west and the oceanic-continental transform margin to the SE. The SFZ formed and bounds the Shipwreck Trough on the eastern side and is interpreted as a N S striking transtensional fault zone, representing the northern en echelon extension of the transform margin to the south. The Shipwreck Trough is the downward thrown (western) side of the SFZ and is host to an array of horst and half-graben structures, two of which contain the producing Geographe and Thylacine gas fields. The Shipwreck Trough and SFZ are imaged by the Investigator 3D seismic dataset, which has previously been studied to conduct 2D restorations and interpret the timing, magnitude, orientation and nature of the structural events of the Shipwreck Trough. Our study adds to this previous research by using spectral decomposition and coherence volumes to further characterise the SFZ (and associated igneous features), basement structural elements and Late Cretaceous horst and half-graben structures. We have identified examples of releasing bend, releasing jog and restraining jog structures along the SFZ that are indicative of sinistral transtensional deformation and have highlighted areas of increased basement fault block relief, which have driven extensional faulting in the cover. We have also conducted throw-distance and throw-depth analysis on four horst and half-graben structures and shown that the associated normal faults have had continuous Late Cretaceous growth with the structures being formed through incidental linkage of normal fault segments. Finally, our two-way-time (TWT) and isochronal mapping of the entire 3D survey shows the development of the Late Cretaceous rifting event in the Shipwreck Trough and highlights numerous other structural closures similar to (and with close vicinity of) the Thylacine and Geographe gas fields, providing implications for prospectivity. [ABSTRACT FROM AUTHOR]

Establishing what controls the timing of earthquakes is fundamental to understanding the nature of the earthquake cycle and critical to determining time-dependent earthquake hazard. Seasonal loading provides a natural laboratory to explore the crustal response to a quantifiable transient force. In California, water storage deforms the crust as snow and water accumulates during the wet wintermonths. We used 9 years of global positioning system (GPS) vertical deformation time series to constrain models of monthly hydrospheric loading and the resulting stress changes on fault planes of small earthquakes. The seasonal loading analysis reveals earthquakes occurring more frequently during stress conditions that favor earthquake rupture. We infer that California seismicity rates are modestly modulated by natural hydrological loading cycles. [ABSTRACT FROM AUTHOR]

Seismic anisotropy beneath the Tian Shan Mt range has been well studied with shear wave splitting. The origin of asthenospheric anisotropy is mainly attributed to the north-south shortening. However, the crustal anisotropy and its depth variation are poorly constrained. In this study, we focus on inversion of Rayleigh wave phase velocity azimuthal anisotropy in the 5–35 s period bands beneath the Tian Shan Mt range through analysis of continuous seismic ambient noise. We use approximately 7 months of available continuous seismic data recorded by 31 broadband seismic stations deployed in the Tian Shan Mt range. The tomographic results reveal substantial variations in the azimuthal anisotropy with an increase in the depth. In the upper crustal depths, the orogen-parallel or orogen-subparallel azimuthal anisotropy observed in the Tian Shan Mt range likely originates from the lattice-preferred orientation of crustal minerals in response to compression, whereas the orogen-perpendicular or orogen-sub-perpendicular azimuthal anisotropy in the southern and northern piedmont of the Tian Shan Mt range is related to the stress-alignment of cracks/fractures due to ongoing north-south shortening. The pattern of azimuthal anisotropy in the middle to lower crustal and upper-most mantle is different from that at the upper crustal depths. An orogen-perpendicular or orogen-sub-perpendicular fast direction associated with prominent lower velocities has been observed north and south of Lake Issyk-Kul. The spatial correlation between the azimuthal anisotropy and the lower velocity anomalies at the middle to lower crustal and upper-most mantle depths may suggest a warm, melt-rich upper mantle below the Tian Shan Mt range, which could be attributed to the upwelling asthenospheric mantle flow in that region. [ABSTRACT FROM AUTHOR]

The present study deals with detecting seismic anisotropy parameters beneath southeastern Tibet near Namcha Barwa Mountain using the splitting of direct S waves. We employ the reference station technique to remove the effects of source-side anisotropy. Seismic anisotropy parameters, splitting time delays, and fast polarization directions are estimated through analyses of a total of 501 splitting measurements obtained from direct S waves from 25 earthquakes (≥5.5 magnitude) that were recorded at 42 stations of the Namcha Barwa seismic network. We observe a large variation in time delays ranging from 0.64 to 1.68s, but in most cases, it is more than 1s, which suggests a highly anisotropic lithospheric mantle in the region. A comparison between direct S- and SKS-derived splitting parameters shows a close similarity, although some discrepancies exist where null or negligible anisotropy has been reported earlier using SKS. The seismic stations with hitherto null or negligible anisotropy are now supplemented with new measurements with clear anisotropic signatures. Our analyses indicate a sharp change in lateral variations of fast polarization directions (FPDs) from consistent SSW–ENE or W–E to NW–SE direction at the southeastern edge of Tibet. Comparison of the FPDs with Global Positioning System (GPS) measurements, absolute plate motion (APM) directions, and surface geological features indicates that the observed anisotropy and hence inferred deformation patterns are not only due to asthenospheric dynamics but are a combination of lithospheric deformation and sub-lithospheric (asthenospheric) mantle dynamics. Direct S-wave-based station-averaged splitting measurements with increased back-azimuths tend to fill the coverage gaps left in SKS measurements. [ABSTRACT FROM AUTHOR]

Continental lithosphere houses the oldest and thickest regions of the Earth's surface. Locked within this deep and ancient rock record lies invaluable information about the dynamics that has shaped and continue to shape the planet. Much of that history has been dominated by the forces of plate tectonics which has repeatedly assembled super continents together and torn them apart - the Wilson Cycle. While the younger regions of continental lithosphere have been subject to deformation driven by plate tectonics, it is less clear whether the ancient, stable cores formed and evolved from similar processes. New insight into continental formation and evolution has come from remarkable views of deeper lithospheric structure using enhanced seismic imaging techniques and the increase in large volumes of broadband data. Some of the most compelling observations are that the continental lithosphere has a broad range in thicknesses (< 100 to > 300 km), has complex internal structure, and that the thickest portion appears to be riddled with seismic discontinuities at depths between ~ 80 and ~ 130 km. These internal structural features have been interpreted as remnants of lithospheric formation during Earth's early history. If they are remnants, then we can attempt to investigate the structure present in the deep lithosphere to piece together information about early Earth dynamics much as is done closer to the surface. This would help delineate between the differing models describing the dynamics of craton formation, particularly whether they formed in the era of modern plate tectonics, a transitional mobile-lid tectonic regime, or are the last fragments of an early, stagnant-lid planet. Our review paper (re)introduces readers to the conceptual definitions of the lithosphere and the complex nature of the upper boundary layer, then moves on to discuss techniques and recent seismological observations of the continental lithosphere. We then review geodynamic models and hypotheses for the formation of the continental lithosphere through time and implications for the formation and preservation of deep structure. These are contrasted with the dynamical picture of modern day continental growth during lateral accretion of juvenile crust with reference to examples from the Australian Tasmanides and the Alaskan accretionary margin. [ABSTRACT FROM AUTHOR]

This paper is focused on analysis of comprehensive experimental research data on the infragravitational range of periods (from 20 s to 10-12 min) obtained by synchronous measurements of fluctuations in deformations of the Earth's crust and atmospheric and hydrospheric pressure variations. It is established that the identified variations in the period range of 1-4 min are rarely observed in records of a laser nanobarograph and laser instrument for measuring hydrospheric pressure variations (laser hydrophone), while they are frequently observed in records of laser strainmeters at a variation period of 3-4 min. Oscillation excitation in the period ranges of 7-13 min, especially in the period ranges of 8-12 min, is largely related to atmospheric processes in the corresponding periods. [ABSTRACT FROM AUTHOR]

In this paper, an improved algorithm is proposed to separate blended seismic data. We formulate the deblending problem as a regularization problem in both common receiver domain and frequency domain. It is suitable for different kinds of coding methods such as random time delay discussed in this paper. Two basic approximation frames, which are iterative shrinkage-thresholding algorithm (ISTA) and fast iterative shrinkage-thresholding algorithm (FISTA), are compared. We also derive the Lipschitz constant used in approximation frames. In order to achieve a faster convergence and higher accuracy, we propose to use firm-thresholding function as the thresholding function in ISTA and FISTA. Two synthetic blended examples demonstrate that the performances of four kinds of algorithms (ISTA with soft- and firm-thresholding, FISTA with soft- and firm-thresholding) are all effective, and furthermore FISTA with a firm-thresholding operator exhibits the most robust behavior. Finally, we show one numerically blended field data example processed by FISTA with firm-thresholding function. [ABSTRACT FROM AUTHOR]

The Alaska earthquake catalog has been analyzed in detail to find and study the diurnal periodicity of earthquake events. For this purpose, a set of spatially and temporally homogeneous samples of earthquakes with the well-known magnitude of completeness ( M) has been prepared. For each sample, the spectra have been considered, the average diurnal variations in the number of earthquakes have been calculated, and their amplitudes were determined. The average diurnal variations were compared. For representative earthquakes in Alaska, no significant diurnal variation has been found. In subrepresentative samples, either the diurnal variation is insignificant or the signal-to-noise ratio only slightly exceeds 1.3-1.9. The diurnal variation is significant (a signal-to-noise ratio of 2.0-4.5) only for the samples of weak earthquakes with magnitudes of no more than 1.4, which is 0.5 units less than the strong (i.e., guaranteed for the entire sample area) completeness threshold. The results are consistent with the hypothesis explaining the diurnal periodicity of earthquakes by noise-discrimination effects. However, a comparative analysis of the diurnal variation parameters estimated over a large number of spatially and temporally homogeneous samples of earthquakes in the Alaska, southern California, and Greece catalogs shows that all of these results cannot be explained by this model. [ABSTRACT FROM AUTHOR]

The GPS-signals recorded as the ionospheric response to the transition of the acoustic waves after a series of the strongest (with magnitude M ≥ 8.2) seaquakes are analyzed. It is shown that the signals may contain information about the energy characteristics of these seismic events. The seismic energy estimates for such events based on the shape of the characteristic perturbation in the ionospheric total electron content (the duration of the compression phase of the shock wave) agree with the estimates inferred from the seismic data and can be obtained within 15 min after the event. [ABSTRACT FROM AUTHOR]

The distribution and formation mechanisms of typical identified seismites are analyzed based on various factors from plate tectonic positions, types of sedimentary basins and properties of seismogenic faults to focal mechanisms. Especially, structural styles, reserved positions, activity times, formation mechanisms and dynamics of soft-sediment deformation structures triggered by seismic activity are systematically analyzed. According to the genetic types of seismites, we propose 5 categories, including liquefied deformation, thixotropic deformation, hydroplastic deformation, superimposed gravity driving deformation and brittle deformation. Further, based on the main genetic types, composition of sediments and deformation styles, we draw up 35 secondary classifications. To determine paleo-seismic sequences in different times, activities of seismogenic faults, high-resolution tectonic events in one main tectonic movement and paleo-tectonic settings, and to understand the inducing mechanisms of paleo-earthquakes and ecologic environment evolution, researching on seismites are of great significance. Combing multiple approaches to identify the paleoearthquake records, simulating experiments on various soft-sediment deformation structures triggered by different magnitudes of shocking, dating precisely on paleo-seismic events, impacting on paleogeography and biological environment and on energy and resources domain are the frontiers of paleoseismic research. [ABSTRACT FROM AUTHOR]

The detection of mixed oscillation modes offers a unique insight into the internal structure of core helium burning (CHeB) stars. The stellar structure during CHeB is very uncertain because the growth of the convective core, and/or the development of a semiconvection zone, is critically dependent on the treatment of convective boundaries. In this study we calculate a suite of stellar structure models and their non-radial pulsations to investigate why the predicted asymptotic g-mode ℓ = 1 period spacing ΔΠ1 is systematically lower than is inferred from Kepler field stars. We find that only models with large convective cores, such as those calculated with our newly proposed 'maximal-overshoot' scheme, can match the average ΔΠ1 reported. However, we also find another possible solution that is related to the method used to determine ΔΠ1: mode trapping can raise the observationally inferred ΔΠ1 well above its true value. Even after accounting for these two proposed resolutions to the discrepancy in average ΔΠ1, models still predict more CHeB stars with low ΔΠ1 (≲ 270 s) than are observed. We establish two possible remedies for this: (i) there may be a difficulty in determining ΔΠ1 for early CHeB stars (when ΔΠ1 is lowest) because of the effect that the sharp composition profile at the hydrogen burning shell has on the pulsations, or (ii) the mass of the helium core at the flash is higher than predicted. Our conclusions highlight the need for the reporting of selection effects in asteroseismic population studies in order to safely use this information to constrain stellar evolution theory. [ABSTRACT FROM AUTHOR]

Volcano seismology, while its value for surveillance of an active volcano is undebatable, is a very demanding field when it comes to station deployment, maintenance, and finally interpreting the measurements. Most valuable in the past was the deployment of arrays of sensors to evaluate the properties of the entire wavefield in order to classify, locate, and estimate the dominant mechanism of the corresponding sources. While very beneficial, an array of seismographs is very hard to maintain in a permanent installation at an active volcano. With the advent of new instrumentation based on fiber optic technology such as Distributed Acoustic Sensing (DAS) with fiber optic cables as well as Fiber-Optic Gyroscopes (FOG) the measurement of deformation and rotation, i.e., the gradient of the wavefield is feasible. The advantage of the FOG instrumentation with respect to DAS lies in the portability and ease of deployment, which is very similar to standard deployments of traditional seismometers. During a field campaign in summer 2018 we were able to install three FOGs together with classical broadband seismometers in close proximity to the active vents of Stromboli volcano (Italy). We show that with this new six-degrees-of-freedom (6DOF) measurement we are able to analyze the wavefield composition, a property normally reserved for array(s) of seismic sensors. As a first result, we can support earlier array-derived findings that a large portion of the wavefield at Stromboli volcano is formed by SV- and SH- type waves. We also present first locations of these signals facilitating the polarization properties of the combined measurement of gyroscopes and seismometers. They emphasize the benefit of recording wavefield gradients. In addition to these array-like results, the 6DOF recordings show a clear separation of at least three distinct groups of volcanic events of which two are already known and one represents a jetting event that appears nearly invisible for classical seismometers. However, rotational motions - or more general - gradients of the wavefield experience severe distortions by local velocity fluctuations and topography significantly complicating the application of 6DOF techniques at activate volcanoes. • First six-degree-of-freedom measurements with a network of rotational motion sensors at an active volcano. • Identification of three visually different types of explosion quakes at Stromboli. • Localization of volcanic sources using the concepts of six-component polarization analysis. • Synthetics and real data reveal complex wave field in the near field of a volcanic source. [ABSTRACT FROM AUTHOR]

This paper provides new insights into the characteristics and uncertainties in railway ground-borne vibration prediction. It analyses over 1500 ground-borne vibration records, at 17 high speed rail sites, across 7 European countries. Error quantification tests reveal that existing scoping models, for at-grade tracks, are subject to a mean error of approximately ±4.5 VdB. Furthermore, it is found that seemingly identical train passages are subject to a standard deviation of ±2 VdB, thus providing an indicator of the minimum error potentially achievable in detailed prediction studies. Existing vibration attenuation relationships are also benchmarked and potential new relationships proposed. Furthermore, it is found that soil material properties are the most influential parameter that effect vibration levels while the effect of train speed is low. In addition, sites with train speeds close to the ‘critical velocity’ are examined and it is found that their vibration characteristics differ vastly from non-critical velocity sites. The study presents one of the most comprehensive publications of experimental ground-borne railway vibration data and comprises of datasets from Belgium, France, Spain, Portugal, Sweden, England and Italy. First, several international metrics are used to analyse the data statistically. Then the effect of train speed is investigated, with train speeds ranging from 72 to 314 km/h being considered. Next the effect of train type is analysed, with correlations presented for TGV, Eurostar, Thalys, Pendolino, InterCity, X2000, Alfa Pendular, AVE-S100 and Altaria trains. Then, vibration frequency spectrums are considered and critical speed effects analysed. Finally, an investigation into the typical standard deviation encountered in vibration prediction is undertaken. [ABSTRACT FROM AUTHOR]

A method to identify the P-arrival of microseismic signals is proposed in this work, based on the algorithm of intrinsic timescale decomposition (ITD). Using the results of ITD decomposition of observed data, information of instantaneous amplitude and frequency can be determined. The improved ratio function of short-time average over long-time average and the information of instantaneous frequency are applied to the time-frequency-energy denoised signal for picking the P-arrival of the microseismic signal. We compared the proposed method with the wavelet transform method based on the denoised signal resulting from the best basis wavelet packet transform and the single-scale reconstruction of the wavelet transform. The comparison results showed that the new method is more effective and reliable for identifying P-arrivals of microseismic signals. [ABSTRACT FROM AUTHOR]

The lithosphere-asthenosphere boundary (LAB) is investigated recently very effectively, mostly using seismic methods because of their deep penetration and relatively good resolution. The nature of LAB is still debated, particularly under 'cold' Precambrian shields and platforms. Passive experiment '13 BB star' is dedicated to study deep structure of the Earth's interior in the marginal zone of the East European craton in northern Poland. The seismic network consists of 13 broadband stations on the area of ca. 120 km in diameter. The network is located in the area of well-known sedimentary cover and crustal structure. Good records obtained till now, and expected during next 1-year long recording campaign, should yield images of detailed structure of the LAB, '410', '?520', and '660' km discontinuities, as well as mantle-core boundary and inner core. [ABSTRACT FROM AUTHOR]

Monitoring the concentration of radon gas is an established method for geophysical analyses and research, particularly in earthquake studies. A continuous radon monitoring station was implemented in Jooshan hotspring, Kerman province, south east Iran. The location was carefully chosen as a widely reported earthquake-prone zone. A common issue during monitoring of radon gas concentration is the possibility of noise disturbance by different environmental and instrumental parameters. A systematic mathematical analysis aiming at reducing such noises from data is reported here; for the first time, the Kalman filter (KF) has been used for radon gas concentration monitoring. The filtering is incorporated based on several seismic parameters of the area under study. A novel anomaly defined as 'radon concentration spike crossing' is also introduced and successfully used in the study. Furthermore, for the first time, a mathematical pattern of a relationship between the radius of potential precursory phenomena and the distance between epicenter and the monitoring station is reported and statistically analyzed. [ABSTRACT FROM AUTHOR]

On 4 March 2008, a moderate earthquake (ML = 5.2) occurred in southern Taiwan and named as the Taoyuan earthquake, preceded by foreshocks and followed by numerous aftershocks. This earthquake sequence occurred during the TAIGER (TAiwan Integrated GEodynamics Research) controlled-source seismic experiment. Consequently, several seismic networks were deployed in the Taiwan area at this time and many stations recorded this earthquake sequence in the near-source region. We archived and processed near-source observations to determine the fault orientation. To locate the events more accurately, station corrections, waveform cross-correlation to pick seismic phases, and a double-difference earthquake location algorithm were used to compute earthquake hypocenters. Over a 50-hour recording period, beginning half an hour before the start of the main shock, 2340 events were identified within the earthquake sequence. The identified aftershocks reveal a clear fault plane with a strike of N37°E and a dip of 45°SE. This plane corresponds to one of the focal mechanism nodal planes determined by the Broadband Array in Taiwan for Seismology (BATS) (strike = 37°, dip = 48°, and rake = 96°). Based on the main shock focal mechanism, the aftershock distribution, and the regional geological reports, we suggest that faulting on the northern extension of the major regional active fault, the Chishan Fault, caused the Taoyuan earthquake sequence. [ABSTRACT FROM AUTHOR]

The 11/5/2011 Lorca, Spain earthquake (Mw $$\,=\,$$ 5.2) and related seismicity produced extensive damage in the town of Lorca and vicinity. During these earthquakes, evidence of rotations and permanent deformations in structures were observed. To analyze these aspects and study the source properties from the near-field, the displacement time histories were obtained including the static component at Lorca station. Displacement time histories were computed by an appropriate double time integration procedure of accelerograms. Using these data, the foreshock and mainshock slip distributions were calculated by means of a complete waveform kinematic inversion. To study the dynamic deformations, the 3D tensor of displacement gradients at Lorca station was first estimated by a single station method. Using the finite fault inversion results and by means of a first order finite difference approach, the dynamic deformations tensor at surface was calculated at the recording site. In order to estimate the distribution of the peak dynamic deformations, the calculation was extended to the close neighboring area of the town. The possible influence of the near-field deformations on the surface structures was analyzed. [ABSTRACT FROM AUTHOR]

We investigate mainshock slip distribution and aftershock activity of the 8 January 2013 M = 5.7 Lemnos earthquake, north Aegean Sea. We analyse the seismic waveforms to better understand the spatio-temporal characteristics of earthquake rupture within the seismogenic layer of the crust. Peak slip values range from 50 to 64 cm and mean slip values range from 10 to 12 cm. The slip patches of the event extend over an area of dimensions 16 × 16 km. We also relocate aftershock catalog locations to image seismic fault dimensions and test earthquake transfer models. The relocated events allowed us to identify the active faults in this area of the north Aegean Sea by locating two, NE-SW linear patterns of aftershocks. The aftershock distribution of the mainshock event clearly reveals a NE-SW striking fault about 40 km offshore Lemnos Island that extends from 2 km up to a depth of 14 km. After the mainshock most of the seismic activity migrated to the east and to the north of the hypocenter due to (a) rupture directivity towards the NE and (b) Coulomb stress transfer. A stress inversion analysis based on 14 focal mechanisms of aftershocks showed that the maximum horizontal stress is compressional at N84°E. The static stress transfer analysis for all post-1943 major events in the North Aegean shows no evidence for triggering of the 2013 event. We suggest that the 2013 event occurred due to tectonic loading of the North Aegean crust. [ABSTRACT FROM AUTHOR]

Seismic hazard analysis requires knowledge of the recurrence rates of large magnitude earthquakes that drive the hazard at low probabilities of interest for seismic design. Earthquake recurrence is usually determined through studies of the historic earthquake catalogue for a given region. Reliable historic catalogues generally span time periods of 100-200 years in North America, while large magnitude events (M ≥ 7) have recurrence rates on the order of hundreds or thousands of years in many areas, resulting in large uncertainty in recurrence rates for large events. Using Monte Carlo techniques and assuming typical recurrence parameters, we simulate earthquake catalogues that span long periods of time. We then split these catalogues into smaller catalogues spanning 100-200 years that mimic the length of historic catalogues. For each of these simulated 'historic' catalogues, a recurrence rate for large magnitude events is determined. By comparing recurrence rates from one historic-length catalogue to another, we quantify the uncertainty associated with determining recurrence rates from short historic catalogues. The use of simulations to explore the uncertainty (rather than analytical solutions) allows us flexibility to consider issues such as the relative contributions of aleatory versus epistemic uncertainty, and the influence of fitting method, as well as lending insight into extreme-event statistics. The uncertainty in recurrence rates of large (M > 7) events is about a factor of two in regions of high seismicity, due to the shortness of historic catalogues. This uncertainty increases greatly with decreasing seismic activity. Uncertainty is dependent on the length of the catalogue as well as the fitting method used (least squares vs. maximum likelihood). Examination of 90th percentile recurrence rates reveals that epistemic uncertainty in the true parameters may cause recurrence rates determined from historic catalogues to be uncertain by a factor greater than 50. [ABSTRACT FROM AUTHOR]

On 23 October 2011 at 1341 local time, a strong earthquake ( Mw = 7.1) occurred east of Lake Van (KOERI; Kandilli Observatory and Earthquake Research Institute). The focal parameters of the main shock and 29 aftershocks with M ≥ 4.0 were obtained from regional broadband seismic data from KOERI network by using Regional Moment Tensor Inversion Code (Dreger ). It is confirmed that the main shock had thrust faulting mechanism. The stress tensor analysis was completed using the focal mechanism solutions and the software developed by (Gephart Comp Geosci 16: 953-989, ). The maximum principal stress ( P compressional) of the main shock is aligned in a N-S (NNW/SSE) direction and the tensional axis ( T dilatation) is aligned in an E-W (ENE-WSW) direction. The b value is calculated as 0.96 using the maximum likelihood method (Utsu ). [ABSTRACT FROM AUTHOR]

Located on the Alpine-Himalayan earthquake belt, Iran is one of the seismically active regions of the world. Northern Iran, south of Caspian Basin, a hazardous subduction zone, is a densely populated and developing area of the country. Historical and instrumental documented seismicity indicates the occurrence of severe earthquakes leading to many deaths and large losses in the region. With growth of seismological and tectonic data, updated seismic hazard assessment is a worthwhile issue in emergency management programs and long-term developing plans in urban and rural areas of this region. In the present study, being armed with up-to-date information required for seismic hazard assessment including geological data and active tectonic setting for thorough investigation of the active and potential seismogenic sources, and historical and instrumental events for compiling the earthquake catalogue, probabilistic seismic hazard assessment is carried out for the region using three recent ground motion prediction equations. The logic tree method is utilized to capture epistemic uncertainty of the seismic hazard assessment in delineation of the seismic sources and selection of attenuation relations. The results are compared to a recent practice in code-prescribed seismic hazard of the region and are discussed in detail to explore their variation in each branch of logic tree approach. Also, seismic hazard maps of peak ground acceleration in rock site for 475- and 2,475-year return periods are provided for the region. [ABSTRACT FROM AUTHOR]

In this study, we describe two experiments of seismic noise measurements carried out in Naples, Italy. The site allowed measurements to be obtained both at the surface and in a tunnel that is 120-m-deep. The main goal was to compare the seismic response evaluated at the surface to the in-tunnel response, through spectral, polarization, and resonance directivity analyses. In the 1 to 20 Hz frequency band, the noise level was up to 15 dB higher at the surface than in the tunnel. The polarization properties and horizontal-to-vertical spectral ratios appear not to be influenced by the tunnel geometry or by the topography. Some preferential alignments were observed in the polarization azimuths computed at the surface, which are likely to be due to local sources, rather than morphological features. The absence of directivity effects and the low noise levels in the tunnel make this site suitable for installing seismic stations. We also studied how the subsoil structure affects the seismic motion at the surface. The dispersive properties of the Rayleigh waves were investigated using the spatial autocorrelation method. A joint inversion of the dispersion data and the horizontal-to-vertical spectral ratios provided the subsurface Vs profile. The derived model has a low velocity contrast at depth, such as to generate moderate and broad H/V spectral ratio peak amplitude. The normalized spectral ratio appears more appropriate to identify the soil-resonance frequencies. [ABSTRACT FROM AUTHOR]

The M 3.2-induced seismic event in 2006 due to fluid injection at the Basel geothermal site in Switzerland was the starting point for an ongoing discussion in Europe on the potential risk of hydraulic stimulation in general. In particular, further development of mitigation strategies of induced seismic events of economic concern became a hot topic in geosciences and geoengineering. Here, we present a workflow to assess the hazard of induced seismicity in terms of occurrence rate of induced seismic events. The workflow is called Forward Induced Seismic Hazard Assessment (FISHA) as it combines the results of forward hydromechanical-numerical models with methods of time-dependent probabilistic seismic hazard assessment. To exemplify FISHA, we use simulations of four different fluid injection types with various injection parameters, i.e. injection rate, duration and style of injection. The hydromechanical-numerical model applied in this study represents a geothermal reservoir with preexisting fractures where a routine of viscous fluid flow in porous media is implemented from which flow and pressure driven failures of rock matrix and preexisting fractures are simulated, and corresponding seismic moment magnitudes are computed. The resulting synthetic catalogues of induced seismicity, including event location, occurrence time and magnitude, are used to calibrate the magnitude completeness M and the parameters a and b of the frequency-magnitude relation. These are used to estimate the time-dependent occurrence rate of induced seismic events for each fluid injection scenario. In contrast to other mitigation strategies that rely on real-time data or already obtained catalogues, we can perform various synthetic experiments with the same initial conditions. Thus, the advantage of FISHA is that it can quantify hazard from numerical experiments and recommend a priori a stimulation type that lowers the occurrence rate of induced seismic events. The FISHA workflow is rather general and not limited to the hydromechanical-numerical model used in this study and can therefore be applied to other fluid injection models. [ABSTRACT FROM AUTHOR]

Oriented collapse of columns, large-scale destruction debris and temporary abandonment of the area deduced from an archaeological excavation provide evidence for a major (intensity IX) earthquake in Patras, Greece. This, and possibly a cluster of other earthquakes, can be derived from archaeological data. These earthquakes are not included in the historical seismicity catalogues, but can be used to put constraints to the seismic risk of this city. Patras was affected by a cluster of poorly documented earthquakes between 1714 and 1806. The city seems to be exposed to risks of progressive reactivation of a major strike-slip fault. A magnitude 6.4 earthquake in 2008 has been related to it. This fault has also been associated with a total of four events in the last 20 years, a situation reminiscent of the seismic hazard at the western edge of the North Anatolian Fault. [ABSTRACT FROM AUTHOR]

Ever since the 1999 Kocaeli earthquake, in which the Kandilli Observatory and Earthquake Research Institute (KOERI) was not able to correctly reflect the magnitude size in its preliminary report because of the saturation effect, a rapid and accurate determination of the earthquake becomes a very important issue. Therefore, in the framework of this study, an automatic determination of the moment magnitude was performed by using the displacement spectra of selected earthquakes in the Marmara Region. For this purpose, 39 three-component broadband stations from KOERI seismic network which recorded 174 earthquakes with magnitudes 2.5 ≤ M ≤ 5.0 in between 2006-2009 were used. Due to the importance of quality factor in determination of the moment magnitude with spectral analysis method, the quality factor was calculated for the whole region in the beginning. Source spectrum which was obtained by converting the velocity records to displacement spectra and moment magnitudes of earthquakes were determined by fitting this spectrum to classical Brune model. For this aim, an automatic procedure was utilized which based on minimizing the differences between observed and synthetic source spectra identified by the S waves. Besides moment magnitude and location parameters, some source parameters such as seismic moment, spectral level, corner frequency and stress drop were also calculated. Application of the method proves that determining the seismic moment from the source spectra is applicable not only for earthquakes with small magnitude but also moderate earthquakes as well. [ABSTRACT FROM AUTHOR]

We propose a method for determining the possible magnitude of a potentially largest induced seismic event derived from the Gutenberg-Richter law and an estimate of total released seismic moment. We emphasize that the presented relationship is valid for induced (not triggered) seismicity, as the total seismic moment of triggered seismicity is not bound by the injection. The ratio of the moment released by the largest event and weaker events is determined by the constants a and b of the Gutenberg-Richter law. We show that for a total released seismic moment, it is possible to estimate number of events greater than a given magnitude. We determine the formula for the moment magnitude of a probable largest seismic event with one occurrence within the recurrence interval (given by one volumetric change caused by mining or injecting). Finally, we compare theoretical and measured values of the moment magnitudes of the largest induced seismic events for selected geothermal and hydraulic fracturing projects. [ABSTRACT FROM AUTHOR]

The paper presents an extensive review of topographic effects in seismology taking into account the knowledge of 40 yr of scientific literature. An overview of topographic effects based on experimental observations and numerical modelling is presented with the aim of highlighting meaning and causes of these phenomena as well as possible correlations between site response (fundamental frequency, amplification level) and geometrical (width and shape ratio of a relief) parameters. After a thorough summary of topographic effects, the paper focuses on five Italian sites whose seismic response is potentially affected by local morphology, as already evidenced by previous studies. In this study, seismic data recorded at these sites are analysed computing directional spectral ratios both in terms of horizontal to vertical spectral ratios (HVSRs) and, wherever possible, in terms of standard spectral ratios (SSRs). The analysis lead to the conclusion that wavefield tends to be polarized along a direction perpendicular to the main axis of a topographic irregularity, direction along which ground motion amplification is maximum. The final section of the article compares and contrasts different spectral ratio techniques in order to examine their effectiveness and reliability in detecting topographic effects. The examples discussed in the paper show that site responses based on HVSRs rather than SSR measurements could lead to misinterpretation of ground response results, both as concerns the definition of the site fundamental frequency and amplification level.Results and findings of this work will be used as starting point to discuss the influence of topographic effects on ground motion prediction equations and regulations for design. These topics will be discussed in the companion article. [ABSTRACT FROM PUBLISHER]

It is shown that episodes of comparative seismic quiescence that lasted about 20-25 years in the areas of study alternated with intervals of sharply increased seismicity as series of large (M ≥ 6.9) earthquakes occurred during two to three decades. Since no M ≥ 6.6 earthquake has occurred in the area for as long as 21 years after the 1992 Susamyr event, middle-term prediction would require identification of zones of imminent large earthquakes. More reliable identification of such zones rests on data relating to inhomogeneities in the field of S-wave attenuation in the lithosphere, as well as on the characteristics of ring structures of seismicity. Such structures are formed as zones of seismic quiescence that are bounded by M ≳ Mth earthquake epicenters, where Mth is the threshold magnitude value. Correlative relationships were previously derived, lgL(Mw) and Mth(Mw), for events with different focal mechanisms (L is the length of the longer axis of a seismicity ring and Mw is the magnitude of the associated large earthquake). These relationships were used to estimate the Mw of large events that can occur in these ring structures. The greatest earthquake with Mw ≳ 7.5 is probably about to occur in southern Tien Shan, east of the 1949 Khait earthquake rupture. A smaller event (Mw ∼ 7.0) can occur in the Kyrgyz Range area. Still smaller earthquakes probably have their precursory areas north and east of Lake Issyk-Kul, as well as in Dzungaria. [ABSTRACT FROM AUTHOR]

The Democratic People Republic of Korea announced two underground nuclear tests carried out in their territory respectively on October 9th, 2006 and May 25th, 2009. The scarce information on the precise location and the size of those explosions has stimulated various kinds of studies, mostly based on seismological observations, by several national agencies concerned with the Nuclear Test Ban Treaty verification. We analysed the available seismological data collected through a global high-quality network for the two tests. After picking up the arrival times at the various stations, a standard location program has been applied to the observed data. If we use all the available data for each single event, due to the different magnitude and different number of available stations, the locations appear quite different. On the contrary, if we use only the common stations, they happen to be only few km apart from each other and within their respective error ellipses. A more accurate relative location has been carried out by the application of algorithms such as double difference joint hypocenter determination (DDJHD) and waveform alignment. The epicentral distance between the two events obtained by these methods is 2 km, with the 2006 event shifted to the ESE with respect to that of 2009. We then used a dataset of VHR TerraSAR-X satellite images to detect possible surface effects of the underground tests. This is the first ever case where these highly performing SAR data have been used to such aim. We applied InSAR processing technique to fully exploit the capabilities of SAR data to measure very short displacements over large areas. Two interferograms have been computed, one co-event and one post-event, to remove possible residual topographic signals. A clear displacement pattern has been highlighted over a mountainous area within the investigated region, measuring a maximum displacement of about 45 mm overall the relief. Hypothesizing that the 2009 nuclear test had been carried out close to the area where the displacement has been observed through the DInSAR technique, its relation with the epicenter location obtained through seismological processing has been discussed as a possible alternative hypothesis with respect to the preferred solutions reported by the nuclear explosion database (NEDB). The distance of about 10 km between the two places can be considered acceptable in light of the possible systematic location shifts commonly observed in the seismological practice over a global scale. The difference between the m magnitudes of the two tests could reflect differences in geological conditions of the two test sites, even if the yield of the two explosions had been the same. [ABSTRACT FROM AUTHOR]

We conduct an experiment to investigate whether linearity in the observed velocity gradient in the volume of the inner core sampled by the PKP ray paths beneath Central America is a robust approximation. Instead of solving an optimization problem, we approach it within the Bayesian inference. This is an ensemble approach, where model specification is relaxed so that instead of only one solution, groups of reasonable models are acceptable. Furthermore, in transdimensional Bayesian inference used here, the number of basis functions needed to model observations is by itself an unknown. Our modeling reveals that in the ensemble of models, the most likely are those containing only 2 nodes (linear trend). Thus our result justifies the assumption used for the determination of inner core rotation with respect to the rest of the mantle that the observed gradient is constant in its nature (linear). Recent observations in seismology suggest that it is likely that the spatial variability in elastic parameters is a widespread phenomenon in the inner core. Future array observations will further constrain spatial extent and magnitude of velocity changes and show whether there is a significant difference between these observations in the two quasi-hemispheres of the inner core. [ABSTRACT FROM AUTHOR]

Ocean bottom seismometer observations at 5000 m depth during the long-range ocean acoustic propagation experiment in the North Pacific in 2004 show robust, coherent, late arrivals that are not readily explained by ocean acoustic propagation models. These 'deep seafloor' arrivals are the largest amplitude arrivals on the vertical particle velocity channel for ranges from 500 to 3200 km. The travel times for six (of 16 observed) deep seafloor arrivals correspond to the sea surface reflection of an out-of-plane diffraction from a seamount that protrudes to about 4100 m depth and is about 18 km from the receivers. This out-of-plane bottom-diffracted surface-reflected energy is observed on the deep vertical line array about 35 dB below the peak amplitude arrivals and was previously misinterpreted as in-plane bottom-reflected surface-reflected energy. The structure of these arrivals from 500 to 3200 km range is remarkably robust. The bottom-diffracted surface-reflected mechanism provides a means for acoustic signals and noise from distant sources to appear with significant strength on the deep seafloor. [ABSTRACT FROM AUTHOR]

A recent dramatic increase in seismicity in the midwestern United States may be related to increases in deep wastewater injection. Here, we demonstrate that areas with suspected anthropogenic earthquakes are also more susceptible to earthquake-triggering from natural transient stresses generated by the seismic waves of large remote earthquakes. Enhanced triggering susceptibility suggests the presence of critically loaded faults and potentially high fluid pressures. Sensitivity to remote triggering is most clearly seen in sites with a long delay between the start of injection and the onset of seismicity and in regions that went on to host moderate magnitude earthquakes within 6 to 20 months. Triggering in induced seismic zones could therefore be an indicator that fluid injection has brought the fault system to a critical state. [ABSTRACT FROM AUTHOR]

Abstract: One of the great classical problems in theoretical seismology is Garvin’s problem, which deals with the response of an elastic half-space subjected to a blast line source applied in its interior. However, Garvin (Exact transient solution of the buried line source problem. Proceedings of the Royal Society of London, Series A 1956;528–541[4]) himself provided only the solution for points on the free surface of the half-space. Although a rigorous extension to points in the interior of the half-space was given nearly decade-and-a-half later by Alterman and Loewenthal (Algebraic expressions for the impulsive motion of an elastic half-space. Israel Journal of Technology 1969; 7 (6):495–504[1]), these scientists published their paper in a technical journal of rather restricted circulation, as a result of which their complete solution remained largely unnoticed by the geophysical and soil dynamics communities. This article revisits Garvin’s generalized problem, presents a concise rendition and summary together with a very effective and accurate simplification, and examines the response characteristics for a pair of buried source-receiver location. It also includes a compact and very effective Matlab program for its evaluation. [Copyright &y& Elsevier]

This paper reviews the Kamchatka seismicity for a 50-year period of observation. These data were used to carry out a regionalization of Kamchatka's seismic volume and adjacent areas. In all, ten zones were identified with differing activities and origins of seismicity. A comparative analysis was carried out for the seismicity in the more active zones. We found significant differences between the structures of the southern and the northern segment in the Kamchatka part of the Kuril-Kamchatka subduction zone. Seismological data corroborated a relationship between the subduction zone and the underthrusting of the Pacific plate under the Eurasian plate. These data from the 50-year period of observation helped identify a new Koryak seismic belt that encompasses the northwestern coast of the Bering Sea. We provide a brief review of macroseismic effects due to the most significant earthquakes for the 1962-2010 period. [ABSTRACT FROM AUTHOR]

This paper presents the main results from the development of the detailed seismological observation system in Kamchatka and the information on the system as of 2011. We describe the networks of seismological stations, the systems for the acquisition, storage, and processing of seismological observations and their technical, methodological, and software support. We discuss the basic characteristics of the recording channels and the system as a whole. We present the information resources of the Kamchatka seismological data bank that provide for basic research in earth sciences. In 2011, the system of seismological observation in Kamchatka was a specialized network for acquisition (recording), storage, transmission, and processing of seismic and geophysical data that provides support for the effective monitoring of seismic and volcanic activities, as well as tsunami warning. [ABSTRACT FROM AUTHOR]

Seismological Observations in Kamchatka were significantly improved due to the installation of new telemetered seismic stations near active volcanoes and the implementation of modern digital technologies for data transmission, acquisition, and processing in 1996-1998. This qualitative leap forward made it possible, not only to create an effective system for monitoring Kamchatka volcanoes and for timely and reliable assessment of the state of these volcanoes, but also to draw conclusions about volcanic hazard. The experience that was gained allowed us to make successful short-term forecasts for eight moderate explosive eruptions on Bezymyannyi Volcano of the ten that have occurred in 2004-2010, successful intermediate-term forecasts of evolving activity on Klyuchevskoi Volcano in three cases, as well as providing a successful forecast of an explosive eruption on Kizimen Volcano. [ABSTRACT FROM AUTHOR]

The article offers information regarding seismic facies analysis of quaternary sediments in the Atlantic Ocean using conducted with low-resolution equipment. It mentions that new data on the fine structure of the sedimentary cover developed over the continental rise and deep basins of the Atlantic Ocean were obtained. It discusses the expedition program which included study of quaternary sedimentary sections on the continental rise and adjacent abyssal basins to define distal turbidites and contourites in these sections, the role of gravitational flows and bottom currents in the formation of sedimentary bodies and climate changes and their influence on oceanic sedimentogenesis carrying out continuous seismoacoustic survey.

SUMMARY Displacement time-series recorded by Global Positioning System (GPS) receivers are a new type of near-field waveform observation of the seismic source. We have developed an inversion method which enables the recovery of an earthquake's mechanism and centroid coordinates from such data. Our approach is identical to that of the 'classical' Centroid-Moment Tensor (CMT) algorithm, except that we forward model the seismic wavefield using a method that is amenable to the efficient computation of synthetic GPS seismograms and their partial derivatives. We demonstrate the validity of our approach by calculating CMT solutions using 1 Hz GPS data for two recent earthquakes in Japan. These results are in good agreement with independently determined source models of these events. With wider availability of data, we envisage the CMT algorithm providing a tool for the systematic inversion of GPS waveforms, as is already the case for teleseismic data. Furthermore, this general inversion method could equally be applied to other near-field earthquake observations such as those made using accelerometers. [ABSTRACT FROM AUTHOR]

SUMMARY The 1909 April 14 Taiwan earthquake caused significant damage in Taipei. Most of the information on this earthquake available until now is from the written reports on its macro-seismic effects and from seismic station bulletins. In view of the importance of this event for assessing the shaking hazard in the present-day Taipei, we collected historical seismograms and station bulletins of this event and investigated them in conjunction with other seismological data. We compared the observed seismograms with those from recent earthquakes in similar tectonic environments to characterize the 1909 earthquake. Despite the inevitably large uncertainties associated with old data, we conclude that the 1909 Taipei earthquake is a relatively deep (50-100 km) intraplate earthquake that occurred within the subducting Philippine Sea Plate beneath Taipei with an estimated MW of 7 ± 0.3. Some intraplate events elsewhere in the world are enriched in high-frequency energy and the resulting ground motions can be very strong. Thus, despite its relatively large depth and a moderately large magnitude, it would be prudent to review the safety of the existing structures in Taipei against large intraplate earthquakes like the 1909 Taipei earthquake. [ABSTRACT FROM AUTHOR]

SUMMARY Two recent major swarms in Western Bohemia occurred in the years 2000 and 2008 within almost the same portion of a fault close to Novy Kostel. Previous analysis of the year 2000 earthquake swarm revealed that fluid intrusion seemed to initiate the activity whereas stress redistribution by the individual swarm earthquakes played a major role in the further swarm evolution. Here we analyse the new swarm, which occurred in the year 2008, with regard to its correlation to the previous swarm as well its spatiotemporal migration patterns. We find that (i) the main part of the year 2008 activity ruptured fault patches adjacent to the main activity of the swarm 2000, but that also (ii) a significant overlap exists where earthquakes occurred in patches in which stress had been already released by precursory events; (iii) the activity shows a clear migration which can be described by a 1-D (in up-dip direction) diffusion process; (iv) the migration pattern can be equally well explained by a hydrofracture growth, which additionally explains the faster migration in up-dip compared to the down-dip direction as well as the maximum up-dip extension of the activity. We use these observations to estimate the underlying fluid pressure change in two different ways: First, we calculate the stress changes induced by precursory events at the location of each swarm earthquake assuming that observed stress deficits had to be compensated by pore pressure increases; and secondly, we estimate the fluid overpressure by fitting a hydrofracture model to the asymmetric seismicity patterns. Both independent methods indicate that the fluid pressure increase was initially up to 30 MPa. [ABSTRACT FROM AUTHOR]

Abstract: A precise determination of ionospheric total electron content (TEC) anomaly variations that are likely associated with large earthquakes as observed by global positioning system (GPS) requires the elimination of the ionospheric effect from irregular solar electromagnetic radiation. In particular, revealing the seismo-ionospheric anomalies when earthquakes occurred during periods of high solar activity is of utmost importance. To overcome this constraint, a multiresolution time series processing technique based on wavelet transform applicable to global ionosphere map (GIM) TEC data was used to remove the nonlinear effect from solar radiation for the earthquake that struck Tohoku, Japan, on 11 March, 2011. As a result, it was found that the extracted TEC have a good correlation with the measured solar extreme ultraviolet flux in 26–34nm (EUV26–34) and the 10.7cm solar radio flux (F10.7). After removing the influence of solar radiation origin in GIM TEC, the analysis results show that the TEC around the forthcoming epicenter and its conjugate were significantly enhanced in the afternoon period of 8 March 2011, 3days before the earthquake. The spatial distributions of the TEC anomalous and extreme enhancements indicate that the earthquake preparation process had brought with a TEC anomaly area of size approximately 1650 and 5700km in the latitudinal and longitudinal directions, respectively. [Copyright &y& Elsevier]

Advances in observational, laboratory, and modeling techniques open the way to the development of physical models of the seismic cycle with potentially predictive power. To explore that possibility, we developed an integrative and fully dynamic model of the Parkfield segment of the San Andreas Fault. The model succeeds in reproducing a realistic earthquake sequence of irregular moment magnitude (Mw) 6.0 main shocks—including events similar to the ones in 1966 and 2004—and provides an excellent match for the detailed interseismic, coseismic, and postseismic observations collected along this fault during the most recent earthquake cycle. Such calibrated physical models provide new ways to assess seismic hazards and forecast seismicity response to perturbations of natural or anthropogenic origins. [ABSTRACT FROM AUTHOR]

Between 1878 and 1880, Switzerland, Italy, and Japan initiated the world's first national earthquake commissions, but only the Swiss made ordinary citizens a vital part of this undertaking. This paper examines the texture of communication between Swiss scientists and lay observers and traces the development of a language for seismology that was simultaneously scientific and vernacular. This is the story of an aborted dialogue between scientists and citizens about living with environmental risk, an alternative abandoned on the way to the increasingly technical science of the twentieth century. [ABSTRACT FROM PUBLISHER]

This paper examines the earthquake monitoring and prediction program, called “collective monitoring, collective defense,” in communist China during the Cultural Revolution, a period of political upheavals and natural disasters. Guided by their scientific and political ideas, the Chinese developed approaches to earthquake monitoring and prediction that emphasized mass participation, everyday knowledge, and observations of macro-seismic phenomena. The paper explains the ideas, practices, and epistemology of the program within the political context of the Cultural Revolution. It also suggests possibilities for comparative analysis of science, state, and natural disasters. The paper redefines the concept of “citizen science” and argues that the concept provides a useful comparative perspective on the intimate relationship between science and the macropolitics of modern state and society. [ABSTRACT FROM PUBLISHER]

Abstract: Ground deformation studies based on Differential GPS (DGPS) measurements and Permanent Scatterer Interferometric (PSI) analysis have been conducted on the islands of Cephalonia and Ithaca covering the period 1992 to 2010. DGPS measurements for the period 2001 to 2010 revealed horizontal clockwise rotation of Cephalonia and velocities ranging from 3 to 8mm/yr with the largest values occurring at the western and southern parts of the island. Considering its vertical deformation, two periods are distinguished on the basis of DGPS and PSI: The first one (1992 to 2003) shows generally an almost linear slight subsidence (around 1mm/yr) which is consistent with expected neotectonic movements of the island. The second one (2003 to 2010) has been tentatively attributed to dilatancy in which reversal to uplift (2–4mm/yr) occurred mainly along the southern and southeastern parts of the island, while larger magnitudes (>4mm/yr) took place at the western part. These non-linear high rates of uplift started at about mid-2005, and were of increasing rate at the southern part, but of decreasing rate at the western part; they may indicate a major regional crustal deformation process in an environment that has previously supported offshore large magnitude earthquakes. Parallel analysis of the observed seismicity in the broader area identified two seismically critical areas on the basis of the decelerating–accelerating seismicity: a major one south of Cephalonia and west of Zakynthos, and another minor one at the NW part of Peloponnese. Critical time estimates of the occurrence of a future strong seismic event in the above critical areas were also made based on: (i) accelerating seismicity, and (ii) the temporal analysis of the seismicity. [Copyright &y& Elsevier]