scholarly journals Regional seismic hazard for Revithoussa, Greece: an earthquake early warning Shield and selection of alert signals

2003 ◽  
Vol 3 (6) ◽  
pp. 757-776 ◽  
Author(s):  
Y. Xu ◽  
P. W. Burton ◽  
G.-A. Tselentis
Keyword(s):  
Seismic Hazard ◽  
Early Warning ◽  
Ground Vibration ◽  
Earthquake Early Warning ◽  
Intensity Level ◽  
Seismic Zone ◽  
Long Distance ◽  
Ground Acceleration ◽  
Gulf Of Corinth ◽  
Strong Ground

Abstract. The feasibility of an earthquake early warning Shield in Greece is being explored as a European demonstration project. This will be the first early warning system in Europe. The island of Revithoussa is a liquid natural gas storage facility near Athens from which a pipeline runs to a gas distribution centre in Athens. The Shield is being centred on these facilities. The purpose here is to analyze seismicity and seismic hazard in relation to the Shield centre and the remote sensor sites in the Shield network, eventually to help characterize the hazard levels, seismic signals and ground vibration levels that might be observed or create an alert situation at a station. Thus this paper mainly gives estimation of local seismic hazard in the regional working area of Revithoussa by studying extreme peak ground acceleration (PGA) and magnitudes. Within the Shield region, the most important zone to be detected is WNW from the Shield centre and is at a relatively short distance (50 km or less), the Gulf of Corinth (active normal faults) region. This is the critical zone for early warning of strong ground shaking. A second key region of seismicity is at an intermediate distance (100 km or more) from the centre, the Hellenic seismic zone south or southeast from Peloponnisos. A third region to be detected would be the northeastern region from the centre and is at a relatively long distance (about 150 km), Lemnos Island and neighboring region. Several parameters are estimated to characterize the seismicity and hazard. These include: the 50-year PGA with 90% probability of not being exceeded (pnbe) using Theodulidis & Papazachos strong motion attenuation for Greece, PGANTP; the 50-year magnitude and also at the 90% pnbe, M50 and MP50, respectively. There are also estimates of the earthquake that is most likely to be felt at a damaging intensity level, these are the most perceptible earthquakes at intensities VI, VII and VIII with magnitudes MVI, MVII and MVIII. Example results (from many) include the corresponding parameters describing the hazard for Revithoussa as follows: PGANTP: 203 cm s- 2 , M50: 6.5, Mp50: 6.9, MVI: 5.8, MVII: 6.1 and MVIII: 6.4. These data are also useful in selecting expected alert-signals i.e. examples of strong ground vibration histories that might be expected at a Shield station in the alert situation.

Source Process-Related Delays in Earthquake Early Warning for Example Cases in Greece

2021 ◽  
Author(s):  
Nikolaos Vavlas ◽  
Anastasia A. Kiratzi ◽  
Zafeiria Roumelioti
Keyword(s):  
Early Warning ◽  
Monitoring Network ◽  
Earthquake Early Warning ◽  
Source Process ◽  
Spatial Density ◽  
Intermediate Depth ◽  
National Monitoring ◽  
Gulf Of Corinth ◽  
Crete Island ◽  
Finite Fault

ABSTRACT We explore a hypothetical zero-latency earthquake early warning (EEW) system in Greece, aiming to provide alerts before warning thresholds of the intensity of ground motion are exceeded. Within the seismotectonic context of Greece, both shallow- and intermediate-depth earthquakes (along the Hellenic subduction zone) are plausible and, thus, examined. Using regionally applicable attenuation relations, we combine and adjust the methodologies of Minson et al. (2018) and Hoshiba (2020) to examine what are the minimum magnitudes required to invoke the warning thresholds at the user site. With simple modeling, we examine how fast an alert can be issued and what is the available warning time when taking into account delays due to finite-fault rupture propagation, alongside other delays. These computations are merged with delays introduced due to the present-day configuration of the Greek national monitoring network (varying spatial density of permanent monitoring stations). This approach serves as a tool to assess the feasibility of an EEW system at specific sites and to redesign the national permanent monitoring network to serve such a system more effectively (we provide results for four sites.). Warning times for on-land crustal earthquakes are found to be shorter, whereas for intermediate-depth earthquakes in Greece an EEW system is feasible (provides warning times of several tens of seconds at large cities, e.g., on Crete Island) even with the current configuration of the national monitoring network, which is quite sparse in the southern part of the country. The current network configuration also provides sufficient early warning (e.g., of the order of 10 s for a warning threshold of 0.05g) at the center of Athens from earthquakes of the eastern Gulf of Corinth—a zone posing elevated hazard in the broader area of the Greek capital. Several additional assumptions and factors affecting the operability of an EEW system in Greece (i.e., source process complexity and uncertainty in attenuation laws) are also discussed.

Robust, an Earthquake Early Warning System in the Lower Rhine Embayment, Germany

2021 ◽  
Author(s):  
Bita Najdahmadi ◽  
Marco Pilz ◽  
Dino Bindi ◽  
Hoby Njara Tendrisoa Razafindrakoto ◽  
Adrien Oth ◽  
...  
Keyword(s):  
Early Warning ◽  
Early Warning System ◽  
Warning System ◽  
Earthquake Early Warning ◽  
Optimization Approach ◽  
Ground Acceleration ◽  
Earthquake Early Warning System ◽  
Scenario Earthquakes ◽  
Lower Rhine Embayment ◽  
Lower Rhine

<p>The Lower Rhine Embayment in western Germany is one of the most important areas of earthquake recurrence north of the Alps, facing a moderate level of seismic hazard in the European context but a significant level of risk due to a large number of important industrial infrastructures. In this context, the project ROBUST aims at designing a user-oriented hybrid earthquake early warning and rapid response system where regional seismic monitoring is combined with smart, on-site sensors, resulting in the implementation of decentralized early warning procedures.<br><br>One of the research areas of this project deals with finding an optimal regional seismic network arrangement. With the optimally compacted network, strong ground movements can be detected quickly and reliably. In this work simulated scenario earthquakes in the area are used with an optimization approach in order to densify the existing sparse network through the installation of additional decentralized measuring stations. Genetic algorithms are used to design efficient EEW networks, computing optimal station locations and trigger thresholds in recorded ground acceleration. By minimizing the cost function, a comparison of the best earthquake early warning system designs is performed and the potential usefulness of existing stations in the region is considered as will be presented in the meeting.</p>

Too-Late Warnings by Estimating Mw: Earthquake Early Warning in the Near-Fault Region

2020 ◽  
Vol 110 (3) ◽  
pp. 1276-1288
Author(s):  
Mitsuyuki Hoshiba
Keyword(s):  
Real Time ◽  
Ground Motion ◽  
Early Warning ◽  
Strong Motion ◽  
Earthquake Early Warning ◽  
Motion Generation ◽  
Near Fault ◽  
Time Gap ◽  
Fault Region ◽  
Strong Ground

ABSTRACT Earthquake early warning (EEW) systems aim to provide advance warnings of impending strong ground shaking. Many EEW systems are based on a strategy in which precise and rapid estimates of source parameters, such as hypocentral location and moment magnitude (Mw), are used in a ground-motion prediction equation (GMPE) to predict the strength of ground motion. For large earthquakes with long rupture duration, the process is repeated, and the prediction is updated in accordance with the growth of Mw during the ongoing rupture. However, in some regions near the causative fault this approach leads to late warnings, because strong ground motions often occur during earthquake ruptures before Mw can be confirmed. Mw increases monotonically with elapsed time and reaches its maximum at the end of rupture, and ground motion predicted by a GMPE similarly reaches its maximum at the end of rupture, but actual generation of strong motion is earlier than the end of rupture. A time gap between maximum Mw and strong-motion generation is the first factor contributing to late warnings. Because this time gap exists at any point of time during the rupture, a late warning is inherently caused even when the growth of Mw can be monitored in real time. In the near-fault region, a weak subevent can be the main contributor to strong ground motion at a site if the distance from the subevent to the site is small. A contribution from a weaker but nearby subevent early in the rupture is the second factor contributing to late warnings. Thus, an EEW strategy based on rapid estimation of Mw is not suitable for near-fault regions where strong shaking is usually recorded. Real-time monitoring of ground motion provides direct information for real-time prediction for these near-fault locations.

scholarly journals Peak ground acceleration at surface for Mataram city with a return period of 2500 years using probabilistic method

2018 ◽  
Vol 195 ◽  
pp. 03019
Author(s):  
Rian Mahendra Taruna ◽  
Vrieslend Haris Banyunegoro ◽  
Gatut Daniarsyad
Keyword(s):  
Seismic Hazard ◽  
Return Period ◽  
Peak Ground Acceleration ◽  
Subduction Zones ◽  
Amplification Factor ◽  
Hazard Analysis ◽  
Probabilistic Method ◽  
Seismic Zone ◽  
Ground Acceleration ◽  
Back Arc

The Lombok region especially Mataram city, is situated in a very active seismic zone because of the existence of subduction zones and the Flores back arc thrust. Hence, the peak ground acceleration (PGA) at the surface is necessary for seismic design regulation referring to SNI 1726:2012. In this research we conduct a probabilistic seismic hazard analysis to estimate the PGA at the bedrock with a 2% probability of exceedance in 50 years corresponding to the return period of 2500 years. These results are then multiplied by the amplification factor referred from shear wave velocity at 30 m depth (Vs30) and the microtremor method. The result of the analysis may describe the seismic hazard in Mataram city which is important for building codes.

Ground Motion Estimation Using Front Site Wave Form Data Based on RVM for Earthquake Early Warning

2015 ◽  
Vol 10 (4) ◽  
pp. 667-677
Author(s):  
Yincheng Yang ◽  
◽  
Masato Motosaka ◽  
Keyword(s):  
Ground Motion ◽  
Early Warning ◽  
Warning System ◽  
Earthquake Early Warning ◽  
Peak Ground Velocity ◽  
Wave Form ◽  
Source Information ◽  
Ground Acceleration ◽  
P Waves ◽  
Earthquake Early Warning System

The use of the earthquake early warning system (EEWS), one of the most useful emergency response tools, requires that the accuracy of real-time ground motion prediction (GMP) be enhanced. This requires that waveform information at observation points along earthquake wave propagation paths (hereafter, front-site waveform information) be used effectively. To enhance the combined reliability of different systems, such as on-site and local/regional warning, we present a GMP method using front-site waveform information by applying a relevant vector machine (RVM). We present methodology and application examples for a case study estimating peak ground acceleration (PGA) and peak ground velocity (PGV) for earthquakes in the Miyagi-Ken Oki subduction zone. With no knowledge of source information, front site waveforms have been used to predict ground motion at target sites. Five input variables – earthquake PGA, PGD, pulse rise time, average period and theVpmax/Amaxratio – have been used for the first 4 to 6 seconds of P-waves in training a regression model. We found that RVM is a useful tool for the prediction of peak ground motion.

A successful approach to earthquake early warning systems

Impact ◽  
2019 ◽  
Vol 2019 (9) ◽  
pp. 18-20
Author(s):  
Pei-Yang Lin
Keyword(s):  
Early Warning ◽  
Seismic Activity ◽  
Peak Ground Acceleration ◽  
Seismic Waves ◽  
Early Warning Systems ◽  
Blind Spot ◽  
Earthquake Early Warning ◽  
Primary Wave ◽  
Ground Acceleration ◽  
Sea Bed

The goal of an earthquake early warning system (EEW) is to identify where and when an earthquake has occurred and then warn those in danger. We think of earthquakes as happening instantaneously but from the detection of the initial event there is time until the effects are noticed. An early warning of even 6 to 19 seconds could allow sensitive infrastructure like factories or power plants to enact automated precautions, reducing damage and allowing for quicker recovery. Warnings of 30 seconds could prevent 95 per cent of potential mortalities in some large cities. It is exactly these crucial seconds that Lin is trying to provide. His team's work centres on developing an integrated EEW for Taiwan which, once proven effective, to help bring this system to other countries who live with the threat of seismic activity.<br/> The EEW developed by Lin works through detecting the seismic waves that earthquakes produce. When an earthquake strikes the ground shakes, this creates seismic waves that move through the earth. These waves, exactly like a ripple in a pond, move out from the epicentre. The first wave, known as the primary wave is low intensity and will not affect structures significantly. The secondary wave however arrives a bit later and causes the intense shaking, damage and casualties. "The goal of the system is to deploy onsite Earthquake Early Waring System(EEWS) to detect the seismic waves and provide warning for the neighborhoods," explains Lin. The regional detectors and EEWS can be deployed to monitor a whole country.<br/> For traditional regional EEWS,like Japan,once a wave is detected the information is sent to a central server which determines the epicentre of the quake, the magnitude of the earthquake and the peak ground acceleration, an important measure of earthquake intensity. "With these measurements the server can then predict where peak ground acceleration will exceed thresholds likely to cause damage and send the alarm," says Lin. The whole process takes only about 15 seconds, which is extremely valuable time for those further away from the epicentre, but because the wave can move up to 90km within these 15 seconds there is a blind spot of about 90km in the regional Earthquake Early Waring System. Lin points out that a blind spot of this size may be fine for some regions. "In Japan the epicentre of the typical hazardous earthquake is in the east sea bed about 100km from the shore but for Taiwan the epicentres are typically below a city. Therefore Lin has developed an integrated approach combining the regional EEW with onsite EEW. The onsite EEWS are installed in cities and monitor local seismic activity. They can predict peak ground acceleration for local area from the primary wave within 1 to 3 seconds and reduce the blind spot to 20 or 30km. Each system has its advantages and disadvantages but integration provides maximum coverage.

Strong ground acceleration seismic hazard in Greece and neighboring regions

2003 ◽  
Vol 23 (2) ◽  
pp. 159-181 ◽  
Author(s):  
Paul W. Burton ◽  
Yebang Xu ◽  
G.-Akis Tselentis ◽  
Ethimios Sokos ◽  
Willy Aspinall
Keyword(s):  
Seismic Hazard ◽  
Ground Acceleration ◽  
Strong Ground

scholarly journals Estimation of Earthquake Early Warning Parameters for Eastern Gulf of Corinth and Western Attica Region (Greece). First Results

Sensors ◽  
2021 ◽  
Vol 21 (15) ◽  
pp. 5084
Author(s):  
Filippos Vallianatos ◽  
Andreas Karakonstantis ◽  
Nikolaos Sakelariou
Keyword(s):  
Early Warning ◽  
Warning System ◽  
Seismic Signal ◽  
Earthquake Early Warning ◽  
Initial Portion ◽  
P Waves ◽  
Peak Displacement ◽  
Earthquake Early Warning System ◽  
Gulf Of Corinth ◽  
Seismic Risk Management

The main goal of an Earthquake Early Warning System (EEWS) is to alert before the arrival of damaging waves using the first seismic arrival as a proxy, thus becoming an important operational tool for real-time seismic risk management on a short timescale. EEWSs are based on the use of scaling relations between parameters measured on the initial portion of the seismic signal after the arrival of the first wave. To explore the plausibility of EEWSs around the Eastern Gulf of Corinth and Western Attica, amplitude and frequency-based parameters, such as peak displacement (Pd), the integral of squared velocity (IV 2) and the characteristic period (τc), were analyzed. All parameters were estimated directly from the initial 3 s, 4 s, and 5 s signal windows (tw) after the P arrival. While further study is required on the behavior of the proxy quantities, we propose that the IV 2 parameter and the peak amplitudes of the first seconds of the P waves present significant stability and introduce the possibility of a future on-site EEWS for areas affected by earthquakes located in the Eastern Gulf of Corinth and Western Attica. Parameters related to regional-based EEWS need to be further evaluated.

scholarly journals Developments of the Nationwide Earthquake Early Warning System in Japan After the 2011 Mw9.0 Tohoku-Oki Earthquake

2021 ◽  
Vol 9 ◽  
Author(s):  
Yuki Kodera ◽  
Naoki Hayashimoto ◽  
Koji Tamaribuchi ◽  
Keishi Noguchi ◽  
Ken Moriwaki ◽  
...  
Keyword(s):  
Point Source ◽  
Ground Motion ◽  
Early Warning ◽  
Prediction Accuracy ◽  
Ground Motions ◽  
Earthquake Early Warning ◽  
Japan Meteorological Agency ◽  
Motion Prediction ◽  
Ground Motion Prediction ◽  
Strong Ground

In Japan, the nationwide earthquake early warning (EEW) system has been being operated by the Japan Meteorological Agency (JMA) since 2007, disseminating information on imminent strong ground motion to the general public and advanced technical users. In the beginning of the operation, the system ran based mainly on standard source-based algorithms with a point-source location estimate and ground motion prediction equation. The point-source algorithms successfully provided ground motion predictions with high accuracy during the initial operation; however, the 2011 Mw9.0 Tohoku-Oki earthquake and the subsequent intense aftershock and triggered earthquake activities underscored the weaknesses of the source-based approach. In this paper, we summarize major system developments after the Tohoku-Oki event to overcome the limits of the standard point-source algorithms and to enhance the EEW performance further. In addition, we evaluate how the system performance was influenced by the updates. One of significant improvements in the JMA EEW system was the implementation of two new ground motion prediction methods: the integrated particle filter (IPF) and propagation of local undamped motion (PLUM) algorithms. IPF is a robust point-source algorithm based on the Bayesian inference, and PLUM is a wavefield-based algorithm that predicts ground motions directly from observed shakings. Another notable update was the incorporation of new observation facilities including S-net, a large-scale ocean bottom seismometer network deployed along the Japan and Kuril trenches. The prediction accuracy and warning issuance performance analysis for the updated JMA EEW system showed that IPF improved the source-based ground motion prediction accuracy and reduced the risk of issuing overpredicted warnings. PLUM made the system less likely to underpredict strong ground motions and improved the warning issuance timeliness. The detection time analysis for the S-net incorporation suggested that S-net enabled the system to issue the first EEW report earlier than before the S-net incorporation for earthquakes around the Japan and Kuril trenches. Those findings indicate that the JMA EEW system has made substantial progress both on software and hardware aspects over the 10 years after the Tohoku-Oki earthquake.

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