Arrival Of Seismic Waves Research Articles

Rapid determination of source parameters for the 2017 Mw 8.2 Mexico earthquake based on high-rate GPS data

Aiming to rapidly determine source parameters (i.e., static offset, seismic wave arrival, moment magnitude, and hypocentral location) for the Mexico 8.2 earthquake, the records of 7 high-rate GPS stations are utilized. Smoothness Priors Method (SPM) is introduced to rapidly extract the static offset from GPS displacement waveforms, and the result suggests this approach is feasible. The seismic wave arrival detection is carried out with the aid of S-transform, and the propagation velocity of seismic wave detected by most GPS stations are within 4–5 km/s, implying the seismic wave captured by GPS station may be S wave or surface wave. After that, an empirical regression model is adopted to characterize the moment magnitude for this earthquake, and this empirical formula can obtain reliable magnitude in comparison with the reference magnitude. The convergence time of average moment magnitude is 298 s, suggesting that a reliable and robust magnitude (Mw 8.37) can be estimated by the 7 GPS stations with about 298 s after earthquake occurrence. Considering the influence of the spatial distribution of GPS stations, 4 nearest GPS stations evenly distributed on both sides of the fault are selected to determine the warning-magnitude for the Earthquake Early Warning (EEW). A reliable and robust moment magnitude (Mw 8.2) can be estimated by the 4 stations with about 251 s, which is 57 s ahead of 7 stations. Finally, the coordinates of 6 GPS stations and corresponding seismic wave arrival time are utilized to determine the hypocentral location, and the latitude and longitude of estimated location is 14.925°N and 93.765°W, which is 17.9 km from the reference location. The results indicate that the source parameters required for EEW can be rapidly determined based on high-rate GPS displacement waveforms, and integrating real-time GPS into a joint EEW system will be crucial going forward.

A seismically induced onshore surge deposit at the KPg boundary, North Dakota

The most immediate effects of the terminal-Cretaceous Chicxulub impact, essential to understanding the global-scale environmental and biotic collapses that mark the Cretaceous-Paleogene extinction, are poorly resolved despite extensive previous work. Here, we help to resolve this by describing a rapidly emplaced, high-energy onshore surge deposit from the terrestrial Hell Creek Formation in Montana. Associated ejecta and a cap of iridium-rich impactite reveal that its emplacement coincided with the Chicxulub event. Acipenseriform fish, densely packed in the deposit, contain ejecta spherules in their gills and were buried by an inland-directed surge that inundated a deeply incised river channel before accretion of the fine-grained impactite. Although this deposit displays all of the physical characteristics of a tsunami runup, the timing (<1 hour postimpact) is instead consistent with the arrival of strong seismic waves from the magnitude Mw ∼10 to 11 earthquake generated by the Chicxulub impact, identifying a seismically coupled seiche inundation as the likely cause. Our findings present high-resolution chronology of the immediate aftereffects of the Chicxulub impact event in the Western Interior, and report an impact-triggered onshore mix of marine and terrestrial sedimentation-potentially a significant advancement for eventually resolving both the complex dynamics of debris ejection and the full nature and extent of biotic disruptions that took place in the first moments postimpact.

Monochromatic infrasound waves observed during the 2014\u20132015 eruption of Aso volcano, Japan

Monochromatic infrasound waves are scarcely reported volcanic infrasound signals. These waves have the potential to provide constraints on the conduit geometry of a volcano. However, to further investigate the waves scientifically, such as how the conduit shape modulates the waveforms, we still need to examine many more examples. In this paper, we provide the most detailed descriptions of these monochromatic infrasound waves observed at Aso volcano in Japan. At Aso volcano, a 160-day-long magmatic eruption occurred in 2014–2015 after a 20-year quiescent period. This eruption was the first event that we could monitor well using our infrasound network deployed around the crater. Throughout the entire eruption period, when both ash venting and Strombolian explosions occurred, monochromatic infrasound waves were observed nearly every day. Although the peak frequency of the signals (0.4–0.7 Hz) changed over time, the frequency exhibited no reasonable correlation with the eruption style. The source location of the signals estimated by considering topographic effects and atmospheric conditions was highly stable at the active vent. Based on the findings, we speculate that these signals were related to the resonant frequencies of an open space in the conduit: the uppermost part inside the vent. Based on finite-difference time-domain modeling using 3-D topographic data of the crater during the eruption (March 2015), we calculated the propagation of infrasound waves from the conduit. Assuming that the shape of the conduit was a simple pipe, the peak frequency of the observed waveforms was well reproduced by the calculation. The length of the pipe markedly defined the peak frequency. By replicating the observed waveform, we concluded that the gas exhalation with a gas velocity of 18 m/s occurred at 120 m depth in the conduit. However, further analysis from a different perspective, such as an analysis of the time difference between the arrivals of infrasound and seismic waves, is required to more accurately determine the conduit parameters based on observational data.

Detection of ground motions using high-rate GPS time-series

Monitoring surface deformation in real-time helps at planning and protecting infrastructures and populations, manages sensitive production (i.e. SEVESO-type) and mitigates long-term consequences of modifications implemented. We present RT-SHAKE, an algorithm developed to detect ground motions associated with landslides, subsurface collapses, subsidences, earthquakes or rock falls. RT-SHAKE detects first transient changes in individual GPS time-series before investigating for spatial correlation(s) of observations made at neighbouring GPS sites and eventually issues a motion warning. In order to assess our algorithm on fast (seconds to minute), large (from 1 cm to metres) and spatially consistent surface motions, we use the 1 Hz GEONET GNSS network data of the Tohoku-Oki Mw9.0 2011 as a test scenario. We show that the delay of detection of seismic wave arrival by GPS records is of ∼10 s with respect to an identical analysis based on strong-motion data and this time delay depends on the level of the time-variable noise. Nevertheless, based on the analysis of the GPS network noise level and ground motion stochastic model, we show that RT-SHAKE can narrow the range of earthquake magnitude, by setting a lower threshold of detected earthquakes to Mw6.5–7, if associated with a real-time automatic earthquake location system.

Neural network model field of the first arrival of seismic waves in Ukraine

Application of DSS data of seismic studies in Ukraine to build models of neural network for time arrival field of seismic signals that allow to construct hodographs of longitudinal waves along arbitrarily oriented sections in regions that do not have seismic observations or to adjust velocity section applying one of the methods of hodograph inversion has been proposed. Comparison of the simulated time of longitudinal wave arrival with those ones that were registered in Ukraine has been made.

EFFECTS OF THE JANUARY 30, 2016, Mw=7.2 ZHUPANOVSKY EARTHQUAKE ON THE WATER LEVEL VARIATIONS IN WELLS YUZ-5 AND E-1 IN KAMCHATKA

This paper describes the water level variations in wells YuZ-5 and E-1 inKamchatkaduring the Zhu­panovsky earthquake that occurred on January 30, 2016 (M w =7.2, Н =180 km). The distances from the Zhupanovsky earthquake epicenter to wells E-1 and YuZ-5 were 70 and 80 km, respectively. In well YuZ-5 , the water level raised by 9.4 cm during 45 minutes after the seismic wave arrival. This effect was caused by a combination of a co-seismic rise in the water level due to the volumetric compression of the water-bearing rocks during fracturing in the earthquake source and an impulse increase in the fluid pressure near the wellbore during the seismic shocks. We estimated the amplitude of the coseismic water level increase (D h =7.3 cm) and the strain value resulting from the volumetric compression of the water-bearing rocks, which is consistent with the estimated value of the coseismic volumetric deformation in the area of the well at the depth of 500m: D 1 = –4.5×10 –8 . This estimation was based on the model of the dislocation source in the homogeneous isotropic elastic half-space with the parameters of the Zhupanovsky earthquake focal mechanism. After the earthquake, the water level dropped for three months at an amplitude of about ~40 cm. In order to estimate the radius of the well sensitivity to the pressure drop source, we used the model of water level lowering that followed the pressure drop in the aquifer at a distance to the well as a result of the improved filtration properties of the water-bearing rocks after the seismic shocks. The estimated radius of the well sensitivity, R is 450 m. For 3.5 months before the Zhupanovsky earthquake, ~20 cm increase in the water level was observed, which is anomalous in comparison with the average seasonal variations of the water level, as shown by the long-term observations. In our opinion, such a rise in the water level occurred in the process of the earthquake preparation, and can thus be viewed as its precursor. In well E-1, a sequence of water level changes manifested a hydrogeodynamic precursor: the water level dropped at an increased rate for 21 days before the earthquake, and raised at an amplitude of 3.7 cm during one month after the earthquake. The hydrogeodynamic precursor detected in real time gave grounds for forecasting a highly probable strong earthquake at a distance of up to 350 km from wells E-1 within a month. This forecast was reported to the Kamchatka Branch of the Russian Expert Council (KB REC) on January 21, 2016. The Zhupanov­sky earthquake occurred on January 30, 2016, and its magnitude, time and location correlated with the prediction. The case of this earthquake shows that the Kamchatka Branch of the Federal Research Center ‘Geophysical Survey of RAS’ has the system of water level observations and data processing, which is capable of diagnosing (close to real time and retrospectively) different types of hydrogeoseismic variations in the water level in wells in case of strong seismic events, and detecting the hydrogeodynamic precursors of strong earthquakes.

Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake.

Transient gravity changes are expected to occur at all distances during an earthquake rupture, even before the arrival of seismic waves. Here we report on the search of such a prompt gravity signal in data recorded by a superconducting gravimeter and broadband seismometers during the 2011 Mw 9.0 Tohoku-Oki earthquake. During the earthquake rupture, a signal exceeding the background noise is observed with a statistical significance higher than 99% and an amplitude of a fraction of μGal, consistent in sign and order of magnitude with theoretical predictions from a first-order model. While prompt gravity signal detection with state-of-the-art gravimeters and seismometers is challenged by background seismic noise, its robust detection with gravity gradiometers under development could open new directions in earthquake seismology, and overcome fundamental limitations of current earthquake early-warning systems imposed by the propagation speed of seismic waves.

An analytical expression for early electromagnetic signals generated by impulsive line-currents in conductive Earth crust, with numerical examples

&lt;p&gt;Changes in the electromagnetic (EM) field after an earthquake rupture but before the arrival of seismic waves (“early EM signals”) have sometimes been reported. Quantitative evaluations are necessary to clarify whether the observed phenomena are accounted for by known theories and to assess whether the phenomenon can be applied to earthquake early warning. Therefore, analytical expressions for the magnetic field generated by an impulsive line-current are derived for a conductive half-space model, and for a two-layer model; the somewhat simpler situation of a conductive whole-space is also considered. By analyzing the expressions obtained for the generated EM field, some expected features of the early EM signals are discussed. First, I verify that an early EM signal arrives before the seismic waves unless conductivity is relatively high. Second, I show that early EM signals are well approximated by the whole-space model when the source is near the ground surface, but not when it is at depth. Third, I show that the expected amplitudes of early EM signals are within the detection limits of commonly used EM sensors, provided that ground conductivity is not very high and that the source current is sufficiently intense. However, this does not mean that the EM signals are easily distinguishable, because detector sensitivity does not account for additive noise or false positive detections.&lt;/p&gt;

Linear traveltime perturbation interpolation: a novel method to compute 3-D traveltimes

Abstract The linear traveltime interpolation has been a routine method to compute first arrivals of seismic waves and trace rays in complex media. The method assumes that traveltimes follow a linear distribution on each boundary of cells. The linearity assumption of traveltimes facilitates the numerical implementation but its violation may result in large computational errors. In this paper, we propose a new way to mitigate the potential shortcoming hidden in the linear traveltime interpolation. We use the vertex traveltimes in a calculated cell to introduce an equivalent homogeneous medium that is specific to the cell boundary from a source. Therefore, we can decompose the traveltime at a point on the cell boundary into two parts: (1) a reference traveltime propagating in the equivalent homogeneous medium and (2) a perturbation traveltime that is defined as the difference between the original and reference traveltimes. We now treat that the traveltime perturbation is linear along each boundary of cells instead of the traveltime. With the new assumption, we carry out the bilinear interpolation over traveltime perturbation to complete traveltime computation in a 3-D heterogeneous model. The numerical experiments show that the new method, the linear traveltime perturbation interpolation, is able to achieve much higher accuracy than that based on the linear traveltime interpolation.

Automatic Seismic Signal Detection via Record Segmentation

The automatic seismic signal detection constitutes a very interesting and challenging task. The main difficulty in solving this problem is attributed to the fact that both the statistical properties of seismic noise and the characteristics of the recorded events are in general unknown. In this paper, by exploiting the particular nature of the signals we are treating, as well as a number of very interesting properties possessed by exchangeable random variables, we formulate the problem at hand as a record segmentation one and propose the use of two functionally linked test statistics for its efficient and robust solution, in a two-step procedure. By following this approach, we succeed not only in detecting a seismic wave arrival, but also in identifying the entire interval occupied by the signal, while minimizing the number of the required parameters. The performance of the proposed technique is confirmed by a series of experiments, both in synthetic and real seismic data sets.

Modeling seismic energy propagation in highly scattering environments

AbstractMeteoroid impacts over millions to billions of years can produce a highly fractured and heterogeneous megaregolith layer on planetary bodies such as the Moon that lack effective surface recycling mechanisms. The energy from seismic events on these bodies undergoes scattering in the fractured layer(s) and generates extensive coda wave trains that follow major seismic wave arrivals. The decay properties of these codas are affected by the planetary body's interior structure. To understand the propagation of seismic waves in such media, we model the transmission of seismic energy in highly scattering environments using an adapted phonon method. In this Monte Carlo simulation approach, we track a large number of seismic wavelets as they leave a source and we record the resulting ground deformation each time a wavelet reaches a surface receiver. Our method provides the first numerical global modeling of 3‐D scattering, with user‐defined power law distributions of scatterer length scales and frequency‐dependent intrinsic attenuation, under the assumption of 1‐D background velocity models. We model synthetic signals for simple, but highly scattering interior models and vary the model parameters independently to assess their individual effects on the coda. Results show that the magnitude of the decay times is most affected by the background velocity model, in particular the presence of shallow low‐velocity layers, the event source depth, and the intrinsic attenuation level. The decay times are also controlled to a lesser extent by the size‐frequency distribution of scatterers, the thickness of the scattering layer, and the impedance contrast at the scatterers.

Tohoku-Oki earthquake caused major ionospheric disturbances at 450 km altitude over Alaska

Ionospheric total electron content (TEC) and atmospheric density perturbations were derived from measurements made from instruments on board the Gravity Recovery and Climate Experiment (GRACE) spacecraft. At the time of the Tohoku-Oki earthquake on 11 March 2011, the twin spacecraft were orbiting at an altitude of ~450 km over Alaska. Significant TEC fluctuations (up to 0.6 total electron content unit (TECU; 1 TECU = 1016 el m−2), atmospheric density perturbations (~3.6 · 10−14 kg/m3), and sudden changes in GRACE acceleration (~4 · 10−8 m/s2) were observed ~8 min after the arrival of seismic and infrasound waves on the ground in Alaska, ~20 min after the Tohoku-Oki main shock at 05:46:23 UTC. The results of the three-dimensional ionospheric-thermospheric modeling and infrasound ray-tracing simulations are consistent with the arrival time and physical characteristics of the disturbances at GRACE. This is the first time that ionospheric disturbances associated with an earthquake are clearly attributable to perturbations at such high altitudes.

Automatic detection and picking of P-wave arrival in locally stationary noise using cross-correlation

Accurate picking of seismic wave arrivals plays a central role in many seismic studies. Nowadays, automatic-picking schemes are indispensable due to the large amount of digital data recorded by wide seismic networks and the need for rapid analysis. The increase of computer power allows the development of more sophisticated algorithms. Many of these algorithms are based on finding change in power, envelope, or statistical properties of the seismic signal in time or frequency domain. But, they have often ignored kind and characteristics of seismic background noise at each recording site. Such information may improve the detector and picker performance if it is taken into account. The aim of this study is to propose a method for picking the arrival of the P-wave in locally stationary seismic background noise. In fact, through analysis of background noise, we have found that it shows local regularity at seismically quiet sites. Therefore, if the background noise satisfies local stationarity, it is evident that occurrence of a seismic event will violate this stationarity. The transition from stationarity to non-stationarity is exploited to pick the P-arrival. To quantify the degree of signal stationarity, we use the normalized cross-correlation function. This method can detect and pick changes both in frequency and amplitude. Thus, it provides robust detection and picking of P-phase onsets even when the signal-to-noise ratio is low. Experimental results on real seismic data, consisting of local seismic events of different signal-to-noise ratios, and comparison with commonly used methods in practice demonstrate the reliable performance of the proposed method.

Teleseismic magnetic effects (TMDs) of 2011 Tohoku earthquake

Anomalous magnetic variations were observed by ground magnetometers in East Asia area after the 2011 Tohoku earthquake. Some earlier reports showed that the seismo‐magnetic variations have obvious amplitude around the epicenter, we emphasis here that the variations can still be notable at stations 2000–4000 km away from epicenter, and we define it as teleseismic magnetic disturbances (TMDs). TMDs appear about 8 min later after the arrival of seismic Rayleigh waves at teleseismic distances and propagate at a horizontal velocity of 3.9 ± 0.1 km/s. The wave‐like TMDs last for no longer than 10 min and have a main period of 2.1–3.3 min. TMDs are not generated by direct effects of processes in focal area crust or tsunami waves, instead, their properties consist with the Rayleigh wave model of seismo‐ionospheric disturbances. Hence, we conclude that the TMDs are the magnetic manifestation of seismotraveling ionospheric disturbances (STIDs) generated by the interaction between the ionosphere and atmosphere through acoustic waves launched by traveling Rayleigh waves. Our findings contribute to the knowledge of seismo‐electromagnetic effects in the atmosphere‐ionosphere system and further our understanding of couplings between various spheres of the Earth.

Determination of Direction of Arrival of Seismic Wave by a Single Tri-axial Fiber Optic Geophone

A fiber Bragg grating (FBG) geophone and a surface seismic wave-based algorithm for the direction of arrival (DOA) are described. The operational principle of FBG geophone is introduced and illustrated with systematic experimental data, demonstrating an improved FBG geophone with many advantages over the conventional geophones. An innovative, robust, and simple algorithm is developed for obtaining the bearing information on the seismic events, such as people walking, or vehicles moving. Such DOA estimate is based on the interactions and projections of surface-propagating seismic waves generated by the moving personnel or vehicles with a single tri-axial seismic sensor based on FBGs. Of particular interest is the case when the distance between the source of the seismic wave and the detector is less than or comparable to one wavelength (less than 100 m), corresponding to near-field detection, where an effective method of DOA finding lacks.

Velocity dispersion in fractured rocks in a wide frequency range

Abstract Experimental measurements of fracture-induced seismic waves velocity variations at frequencies ~ 1 kHz, ~ 40 kHz and ~ 1 MHz were performed directly in the field at the rocky outcrop and in the laboratory on specific rock samples collected from the outcrops. The peridotite–lherzolite outcrop appeared macroscopically uniform and contained three systems of visible parallel sub-vertical fractures. This rock has substantial bulk density and higher than average value of seismic wave velocity. The presence of fracture systems gives rise to its velocity anisotropy. The seismic waves passing through the rock fractures are subject to velocity dispersion and frequency dependent attenuation. Our data, obtained from field and laboratory measurements, were compared with theoretical model predictions. In this model we successfully used displacement discontinuity approach. For the velocity dispersion evaluation we used multi-frequency measurements. The a priori observation of orientations and densities of fracture sets allowed evaluation of their stiffness. Our approach revealed that the first arrivals of seismic waves can be used for evaluation of P-wave group velocities, the specific case, in which we expect anomalous velocity dispersion. Our observations contribute to the issue of up-scaling of well-log derived velocities in fractured rock to the scale of standard seismic exploration frequencies.

Ionospheric disturbances (infrasound waves) over the Czech Republic excited by the 2011 Tohoku earthquake

A train of large amplitude infrasound wave packets was observed by multipoint Continuous Doppler sounding system in the ionosphere over the Czech Republic on 11 March 2011. It is shown that these infrasound wave packets originated from vertical motion of the ground surface that was caused by arrival of seismic waves generated by the strong Tohoku earthquake. The infrasound wave packets were observed in the ionosphere at heights of ∼210–220 km about 9 min after the detection of corresponding wave packets on the ground, which is consistent with the calculated time for vertically propagating infrasound waves. Absolute values of cross‐correlation coefficients between ionospheric and ground measurements are typically higher than 0.9 (for two wave packets ∼0.98). The individual wave packets recorded on the ground have different observed horizontal velocities and correspond to different types of seismic waves. A comparison of vertical velocities of ground motion with oscillation velocities of air particles in the ionosphere indicates that almost 1/10 of the infrasound energy flux excited at the ground reached the altitudes of ∼210–220 km for wave periods longer than ∼30 s. Estimates of sound attenuation are performed. It is also shown that it is necessary to consider the value of electron density gradient at the reflection height of the sounding radio wave, and air (plasma) compression owing to the infrasound wave to get reasonable estimates of oscillation velocities of air particles from Doppler shift frequencies.

Classification of near-surface anomalies in the seismic refraction method according to the shape of the time–distance graph: A theoretical approach

Abstract In this paper, we analyse the influence of near-surface anomalies on the first arrivals of seismic waves. The traveltimes of first arrivals are calculated using the eikonal equation and are depicted in the form of the time–distance ( t – x ) graphs. We classify five simple geological models according to the shape of the t – x graphs and relate these results to more complex models one can find in the natural settings. All simple models are based on the two-layer model that is modified by a near-surface anomaly. We investigate the following cases: (i) a circular cavity impenetrable to seismic waves positioned in the upper layer, (ii) a circular object positioned in the upper layer, (iii) a part of the border between the layers is deformed into concave shape, (iv) a part of the border between the layers is deformed into convex shape, and (v) a vertical fractured zone positioned in the lower layer. The resulting t – x graphs are classified according to their shapes into three groups. The graphs in the first group are characterised by a peak point and the geological models (i) and (iii) belong to this group. The graphs in the second group are characterised by a depression in their shape and the geological models (ii) and (iv) belong to this group. The graph that corresponds to the model (v) differs from all other graphs and belongs to the third group. The seismic refraction method clearly distinguishes the models that belong to different groups, but the method cannot distinguish the models that belong to the same group because the shapes of their t – x graph are almost identical.

Effects of 2D Random Velocity Heterogeneities in the Mantle Lid and Moho Topography on Pn Geometric Spreading

Pn-wave energy refracts through the uppermost mantle, with the first seismic wave arrival at distances of ∼200 to ∼1500 km from crustal sources. The Pn phase provides important constraints on source type, location, and magnitude, but its propagation is complicated by frequency-dependent sensitivity to the Earth's sphericity and lithospheric velocity structure. Converging on an acceptable Pn geometric spreading correction and specifying its uncertainties, a requirement for accurately determining frequency-dependent attenuation models for Pn, depends on improved understanding of the behavior of Pn geometric spreading for various heterogeneous models. We investigate the effects of radial mantle lid velocity gradi- ents, mantle lid random volumetric velocity heterogeneities, and Moho topography on Pn geometric spreading using reflectivity and two-dimensional (2D) finite-difference 1-Hz wave propagation calculations for elastic Earth models. Mantle lid velocity gra- dients systematically modify the frequency-dependent geometric spreading from that found for models with constant velocity but retain the same overall functional form. Pn amplitudes are also sensitive to the presence of modest 2D random lateral velocity heterogeneities within the uppermost mantle, with geometric spreading approaching a power-law behavior as the root mean square strength of heterogeneity increases. 2D Moho topography introduces scatter into the amplitude of Pn, but the overall behavior remains compatible with that for a laterally homogeneous model. Given the lack of knowledge of specific small-scale structure for any particular Pn path, the preferred geometric spreading parameterization is the frequency-dependent model for a constant mantle lid velocity structure unless Pn travel-time branch curvature can constrain the radial gradient in the mantle lid.

Earthquake early warning as a tool for improving society’s resilience and crisis response

Increasing vulnerability of metropolitan areas to earthquake and the very low probability level at which short term earthquake forecasting is possible make earthquake early warning methods (EEW) the main viable alternative for effective risk reduction in cities. Preventive actions, such as retrofitting and building and the diffusion of construction codes, are of course essential. They are not sufficient. A substantial proportion of the population in areas of higher earthquake hazard still reside in buildings that do not meet modern earthquake resistant standards, and cannot currently be strengthened in an economically viable manner. As demonstrated in Japan EEW has the potential of significantly contributing to reduce individual vulnerability of urban population to earthquakes. Future research on EEW should be focused on its implementation to protect lifelines, infrastructures and strategic buildings, and it should include training of administrators and people who can fully exploit the technological advantages offered by EEW systems. In particular it should foresee extensive cost-benefit analysis for each potential application, the identification and solution of legal problems (such as liability in the event of false or missed alarms), education and training, both for mitigation and response, as well as detection and processing within 1 s of the first seismic wave arrivals. Further objectives include the development of people-centred EEW, specialized IT and decision making support systems, integration of sensors, communications and decision making systems, integration into programs of eco-sustainable development, and integration with other EW systems (all hazard systems).