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Evolution of the Kandilli Observatory and Earthquake Research Institute (KOERI) Seismic Network and the Data Center Facilities as a Primary Node of EIDA
Abstract
As the earliest institute in Turkey dedicated to locating, recording, and archiving earthquakes in the region, the Kandilli Observatory and Earthquake Research Institute (KOERI) has a long history in seismic observation, which dates back to the installation of its first seismometers soon after the devastating Istanbul earthquake of 10 July 1894. For over a century, since the deployment of its first seismometer, the KOERI seismic network has grown steadily in time. In this article, we present the KOERI seismic network facilities as a data center for the seismological community, providing data and services through the European Integrated Data Archive (EIDA) and the Rapid Raw Strong-Motion (RRSM) database, both integrated in the Observatories and Research Facilities for European Seismology (ORFEUS). The objective of this article is to provide an overview of the KOERI seismic services within ORFEUS and to introduce some of the procedures that allow to check the health of the seismic network and the quality of the data recorded at KOERI seismic stations, which are shared through EIDA and RRSM.
... This consists of the North Anatolian Fault Zone (NAFZ), East Anatolian Fault Zone (EAFZ) and South Eastern Anatolian Thrust Zone (SAT) which form the borders of the Anatolian Plate and important active fault segments throughout Western Anatolia. All these active faults cause a short time intervals intensive damages in Turkey earthquakes, which in turn is a significant risk of earthquake in Turkey [1]. ...
... Real-time seismology is achieved by three kind sof seismological observations which are phase readings, waveforms and catalogues [1].The earthquake catalogues are the first output of seismological observations. Several institutions around the world generate national and international catalogues for understanding the seismic activity of a region. ...
... Events are recorded real time at the monitoring center digital form obtained from broad-band stations. These are processed using HYPO71 for the hypocenter determination [1]. The seismological division of KOERI determines, as rapidly and accurate as possible, location and size of all earthquakes of magnitude commonly larger than 2.0 that occur in the country [1]. ...
Turkey is between three major tectonic plates, is the most active area of the Mediterranean region in terms of earthquake activity. Relative motions between the African, Arabian and Eurasian plates account for most of the tectonic activity in the region. As a result, the Anatolian plate has a high danger for seismicity. This consists of the North Anatolian Fault Zone (NAFZ), East Anatolian Fault Zone (EAFZ) and SE Anatolian Thrust Zone which form the borders of the Anatolian Plate and important active fault segments throughout Western Anatolia. All these active faults cause a short time intervals intensive damages in Turkey earthquakes. In order to investigate and to real-time monitor the seismic activity and seismotectonic of Turkey and its vicinity, The Kandilli Observatory and Earthquake Research Institute (KOERI) of Bogaziçi University and AFAD operates seismic stations countrywide. Observatory has been supplying mainly 3 kind of seismological data: phase readings, waveform and catalogue to the earth scientists in Turkey. Earth science studies have an important contribution to the emergence of earthquake hazard. The evaluation of the data receiving from the seismic stations contributes to the determination of earthquake hazard in detail, and to contribute to the minimization of the risks of the earthquake by developing earthquake catalogues. Also, all of the earthquake parameters after the earthquake, automatically distributed and mapped. After an important earthquake, KOERI and AFAD is quickly sent information from the smartphones to the society and the decision-making institutions carrying out disaster studies.
... Primarily driven by governmental mandates to detect local seismicity and provide earthquake information to civil protection agencies and the general public, this monitoring effort also results in a tremendous amount of high-quality data-more than 12,000 stations presently contribute to the European Integrated Data Archive (EIDA)-which is made available to scientists and practitioners. This lively community of seismic data providers and users is at the core of the success of this focus section: 30 groups responded enthusiastically to our call for papers, providing high-quality contributions that describe the state of the art in observational seismology in the greater European region, addressing all components of the life cycle of seismic data, from station design to open dissemination of data and seismological products (Amato et al., 2021;Bono et al., 2021;Bragato et al., 2021;Büyükakpınar et al., 2021;Cambaz et al., 2021;Carrilho et al., 2021;Danecek et al., 2021;Evangelidis et al., 2021;Galea et al., 2021;Heit et al., 2021;Lanzano et al., 2021;Lenhardt et al., 2021;Lund et al., 2021;Mărmureanu et al., 2021;Margheriti et al., 2021;Masson et al., 2021;Mader and Ritter, 2021;Ottemöller et al., 2021;Quinteros, Strollo,et al., 2021;Quinteros, Carter, et al., 2021;Rudzinski et al, 2021;Péquegnat et al., 2021;Schweitzer et al., 2021;Senturk et al., 2021;Shahvar et al., 2021;Spallarossa et al., 2021;Stammler et al., 2021;Strollo et al., 2021;Veikkolainen et al., 2021). ...
... Most of the articles of this focus section serve as good examples in the open science domain, in which data are expected to be "findable, accessible, interoperable, and reusable" (Wilkinson et al., 2016). In many contributions, emphasis is placed on quality: as automated access to seismological archives via standardized web services emerges as the preferred user strategy, ensuring the high quality of data and metadata becomes more and more important (e.g., Büyükakpınar et al., 2021;Cambaz et al., 2021;Carrilho et al., 2021;Evangelidis et al., 2021;Mader and Ritter, 2021;Ottemöller et al., 2021;Péquegnat et al., 2021;Stammler et al., 2021;Strollo et al., 2021). Quality is especially important at a time when very large datasets are increasingly being processed routinely and "blindly" in machine-learning approaches. ...
Observational seismology in Europe is firmly rooted innational and regional observatories in charge of managingmore than 100 permanent seismic networks and more than200 past and present temporary deployments. Primarily drivenby governmental mandates to detect local seismicity and pro-vide earthquake information to civil protection agencies andthe general public, this monitoring effort also results in a tre-mendous amount of high-quality data—more than 12,000 sta-tions presently contribute to the European Integrated DataArchive (EIDA)—which is made available to scientists andpractitioners. This lively community of seismic data providersand users is at the core of the success of this focus section [...]
... With the development of network facilities and the internet, the lives of people are tightly surrounded by the internet. Network intrusion is also constantly increasing [1,2]. In addition, the development of network technology gradually makes network intrusion universal and low-cost, which increases the difficulty of network intrusion detection [3]. ...
The commonly used method for network intrusion is based on pattern matching systems, but these systems do not have high detection accuracy when facing large-scale high-speed network traffic environments. In addition, when facing a wide variety of network attacks, relying solely on a certain network security technology is difficult to ensure network security. Therefore, a distributed network intrusion prevention system based on the Spark framework and dynamic information security theory model was innovatively proposed to improve the detection efficiency of network intrusion and solve these issues. The architecture and functional structure of the network intrusion prevention system were constructed by improving the random forest algorithm and Spark. In addition, the dynamic network intrusion prevention system was designed on the basis of the Policy Protection Detection Response (P2DR) model and the Protection Detection Reaction Recovery (PDRR) model to cope with the diverse network attacks and make up for the lack of dynamic defense based on improved forest algorithm and Spark. The test results showed that the network intrusion prevention system based on the improved random forest algorithm and Spark had a maximum detection time of 13,593 ms, a minimum detection time of 13,318 ms, and an average detection time of 13,468 ms when the data were 6000 pieces. The average success rate of the dynamic network intrusion prevention system based on the dynamic information security theory model was 87.72%, the average detection rate was 71.68%, and the average false alarm rate was 17.23%. The F1 values corresponding to the improved random forest algorithm under 7 different attack types of data were 0.985, 0.983, 0.876, 0.843, 0.797, 0.983, and 0.890, respectively, which were significantly better than the comparison algorithm. It can be seen that the dynamic network intrusion prevention system based on the improved random forest algorithm, Spark, and the dynamic information security theoretical model, has good performance and can effectively detect network intrusions, providing technical support for solving network intrusion problems in reality. The contribution of the research is reflected in the improvement of the detection performance of network intrusion detection systems and the reduction of detection time and false alarm rates.
... afad.gov.tr/event-catalog, last access: 14/06/2023) between 6th of February 2023 and 31st of March 2023. In total, 287879 traces are collected from the Turkish National Seismic Network (52 stations) (Disaster and Emergency Management Authority 1990), the Turkish National Strong Motion Network (143 stations) (Disaster and Emergency Management Authority 1973), and Kandilli Observatory and Earthquake Research Institute (KOERI, 6 stations) (Kandilli Observatory And Earthquake Research Institute 1971; Cambaz et al. 2021), all of which are recorded from accelerometric stations. The location of the earthquakes and stations is presented in Fig. 2 and EC8 site classification of the stations is given in Table 1. ...
On the 6th of February 2023, a large magnitude earthquake (Pazarcık earthquake), $$M_{w}=$$ M w = 7.7, occurred in southeast Türkiye, which caused significant destruction in Türkiye and Syria. Relatively large magnitude aftershocks followed the main shock, and after 9 hours of the main event, another large magnitude earthquake (Elbistan earthquake) occurred, $$M_{w}=$$ M w = 7.6, on a nearby fault. This study analyzes the near-fault seismic signals from earthquakes larger than 5.5 recorded between the main shock and the 31st of March 2023. More than 60 impulsive motions are detected in 3 earthquakes, mostly concentrated in the Pazarcık and Elbistan earthquakes. In the Pazarcık earthquake, many impulsive motions are recorded in near-fault stations with periods of up to 14 s. In contrast, in the Elbistan earthquake, impulsive motions are spatially distributed, with pulse periods of up to 11 s and at distances greater than 150 km. Pulse periods mostly correlate with the magnitude of the earthquake, but pulse probability models do not predict impulsive motions over long distances. The presence of strong impulsive motions in vertical components is also observed. For both earthquakes, peak ground velocities (PGVs) are larger than predicted by ground motion prediction equations. The observation of long-period, large amplitude signals may indicate the presence of a directivity effect for both earthquakes. In some stations, spectral periods exceed the 2018 Turkish building design codes for long periods ( $$\ge$$ ≥ 1 s).
... Historical and current reported earthquake fatalities in this region are quite prominent (Figure 1). A long history of destructive earthquakes motivated Türkiye to build a dense seismic monitoring network and to continuously update seismic hazard maps and building codes (Cambaz et al., 2021;AFAD, 2023) while investing further in earthquake research (Inan et al., 2007). The 1999 disaster further accelerated the process of updating building codes in 2007. ...
Despite significant scientific advances in earthquake research and building codes, Türkiye remains vulnerable to earthquakes, as demonstrated by the tragic Kahramanmaraş earthquake in February 2023. In contrast, countries such as Chile and Japan have successfully reduced earthquake damage through strict enforcement of building codes and effective public awareness campaigns. This paper highlights the need for seismic resilience in Türkiye and proposes actionable guidelines to bridge the gap between science and society. These guidelines include comprehensive geoscience education, the establishment of local earthquake centers, effective science communication, preparation for future earthquakes through scenario modeling, and development of an earthquake culture. Geoscience education should be integrated into the education system, and opportunities for geoscientists should be increased. Local earthquake centers can improve seismic monitoring, research, and public outreach. Geoscientists should prioritize science communication training to engage the public and combat misinformation. Scenario modeling and annual preparedness exercises can improve earthquake preparedness across the country, and promoting earthquake memory and awareness initiatives will build a collective consciousness about earthquakes. By implementing these guidelines, Türkiye can build earthquake resilience and mitigate the impact of future earthquakes; however, the active engagement of scientists, institutions, and the public is essential to achieve earthquake resilience.
... Evangelidis et al., 2021), for KO from the Kandilli Observatory and Earthquake Research Institute (KOERI) data center node (EIDA@KOERI; http://eida.koeri.boun.edu.tr; Cambaz et al., 2021), and for TK, TU from the Earthquake Data Center System of Turkey (TDVMS; https://tdvms.afad.gov.tr). The National Observatory of Athens (NOA) manual catalog was retrieved from the EIDA@NOA FDSNWS-event service at https://eida.gein.noa.gr/fdsnws/event/1, ...
The 2020 Mw 7.0 Samos earthquake (eastern Aegean Sea) provides a rare chance to study the ongoing interaction of normal and strike‐slip faulting during an aftershock sequence in a suspected transfer zone with differential deformation style. After assessing them for possible site‐effect influence, we first backproject local strong‐motion data to elicit the high‐frequency (HF) radiation for the main seismic event using the Source Scanning Algorithm. Our results indicate the existence of multiple HF radiators during the main rupture. Second, we construct a new, high‐precision catalog for the aftershock sequence utilizing a deep‐learning‐based detector and picker. This new catalog contains thousands of additional seismic events compared with the routine catalogs built by local agencies and is accompanied by an enhanced dataset of fault‐plane solutions determined with automated techniques. Complex fault networks activated during the aftershock period are mapped in detail, indicating the existence of an active transtensional, possibly asymmetric, basin offshore Samos Island. This detailed seismological characterization of Samos sequence leads to an improved understanding of the controlling mechanisms that operate concurrently during a sequence in a transtensional type of system.
... Seismic monitoring facilities have continued for more than a century since the installation of the first seismometer in 1895. Details of KOERI earthquake catalogues [5,6] and seismic network evolutions [6,7] have been presented in earlier studies. In order to obtain reliable earthquake parameters, today REMTC operates a seismic network including 256 sensors that comprise broadband (BB), accelerometer (SM) and short-period (SP) seismometers. ...
A tsunami warning system providing services in the Eastern Mediterranean, Aegean, Marmara and Black Seas under the UNESCO Intergovernmental Oceanographic Commission (IOC)—Intergovernmental Coordination Group (ICG) for the Tsunami Early Warning and Mitigation System in the North-Eastern Atlantic, the Mediterranean and Connected Seas (NEAMTWS) framework was established in Turkey by the Kandilli Observatory and Earthquake Research Institute (KOERI) (Özel et al., 2011). KOERI’s Regional Earthquake and Tsunami Monitoring Center (RETMC) was established on the foundations of the legacy KOERI National Earthquake Monitoring Center (NEMC) by adding observation, analysis and operational capability related to tsunami early warnings after an extensive preparatory period during 2009 and 2011. The center initiated its test-mode 7/24 operational status as a national tsunami warning center in 2011, and after a one year period it became operational as a candidate tsunami warning center for NEAMTWS on 1 July 2012, together with CENALT (Centre d’Alerte aux Tsunamis—France) and followed by the NOA (National Observatory of Athens—Greece) on 28 August 2012, INGV (Instituto Nazionale di Geofisica e Vulcanologia—Italy) on 1 October 2014 and IPMA (Instituto Português do Mar e da Atmosfera—Portugal) on 1 February 2018, completing full coverage of the tsunami-prone regions monitored by NEAMTWS. In this paper, an overview of the progress and continuous improvement of KOERI’s tsunami early warning system will be presented, together with lessons learned from important tsunamigenic events, such as the 20 July 2017 Bodrum–Kos Mw 6.6 and 30 October 2020 Samos–Izmir Mw 6.9 earthquakes. Gaps preventing the completion of an effective tsunami warning cycle and areas for future improvement are also addressed.
... Evangelidis et al. [2021] followed our approach to test the sensor orientations of the seismic networks of Greece and Cyprus. Cambaz et al. [2021] applied the toolbox in a second study to the KOERI network. In addition, I used the tool to investigate gain problems and sensor orientations prior to single and multi station analyses in Mayotte where only few remote stations are available [Cesca, 2020]. ...
Centroid moment tensor inversion can provide insight into ongoing tectonic processes and active faults. In the Alpine mountains (central Europe), challenges result from low signal-to-noise ratios of earthquakes with small to moderate magnitudes and complex wave propagation effects through the heterogeneous crustal structure of the mountain belt. In this thesis, I make use of the temporary installation of the dense AlpArray seismic network (AASN) to establish a work flow to study seismic source processes and enhance the knowledge of the Alpine seismicity. The cumulative thesis comprises four publications on the topics of large seismic networks, seismic source processes in the Alps, their link to tectonics and stress field, and the inclusion of small magnitude earthquakes into studies of active faults. Dealing with hundreds of stations of the dense AASN requires the automated assessment of data and metadata quality. I developed the open source toolbox AutoStatsQ to perform an automated data quality control. Its first application to the AlpArray seismic network has revealed significant errors of amplitude gains and sensor orientations. A second application of the orientation test to the Turkish KOERI network, based on Rayleigh wave polarization, further illustrated the potential in comparison to a P wave polarization method. Taking advantage of the gain and orientation results of the AASN, I tested different inversion settings and input data types to approach the specific challenges of centroid moment tensor (CMT) inversions in the Alps. A comparative study was carried out to define the best fitting procedures. The application to 4 years of seismicity in the Alps (2016-2019) substantially enhanced the amount of moment tensor solutions in the region. We provide a list of moment tensors solutions down to magnitude Mw 3.1. Spatial patterns of typical focal mechanisms were analyzed in the seismotectonic context, by comparing them to long-term seismicity, historical earthquakes and observations of strain rates. Additionally, we use our MT solutions to investigate stress regimes and orientations along the Alpine chain. Finally, I addressed the challenge of including smaller magnitude events into the study of active faults and source processes. The open-source toolbox Clusty was developed for the clustering of earthquakes based on waveforms recorded across a network of seismic stations. The similarity of waveforms reflects both, the location and the similarity of source mechanisms. Therefore the clustering bears the opportunity to identify earthquakes of similar faulting styles, even when centroid moment tensor inversion is not possible due to low signal-to-noise ratios of surface waves or oversimplified velocity models. The toolbox is described through an application to the Zakynthos 2018 aftershock sequence and I subsequently discuss its potential application to weak earthquakes (Mw<3.1) in the Alps.
Spatial distributions of seismic energy (seismic energy fields) in the vicinity of the epicenter of the October 30, 2020 Aegean Sea Earthquake (\(M \approx 7\)) have been investigated by the multifractal analysis methods. It is shown that the singularity spectrum of the seismic energy field before the main shock of this event had undergone significant widening and asymmetry changing. From the physical point of view, these changes can be explained by seismogenerating system transition into strongly nonequilibrium state before the main shock. Quantitative characteristics of the revealed effects which can be used in the methods of seismogenerating medium current state monitoring are proposed.KeywordsEarthquakesSeismic energyMultifractal\(f\left( a \right)\)-spectrum asymmetry\(f\left( a \right)\)-spectrum widening
The earthquake (Mw 6.9) that occurred in the northern part of Samos Island and Doğanbey-İzmir offshore in the Aegean Sea at 14:51
local time on October 30, 2020 was felt in İzmir, Samos Island and many surrounding cities and settlements. Considering the
earthquake intensity map, contrary to what is expected, the highest impact occurred in Bayraklı district, which is 70 km away from the
epicenter, and caused not only severe structural damage but also fatalities in the region. When the structural damages are evaluated,
determining the local soil properties has an important place in the studies to predict the effects of a possible earthquake. The HVSR
(Horizontal Vertical Spectral Ratio) method provides an advantage in determining the soil fundamental frequency and the soil
amplification factor in the event of an earthquake, in that it can be widely used even in the seismically in-active regions. In this study,
it is not only aimed to analyze the earthquake and ambient noise data obtained from the accelerometer and velocity stations but also
to compare the results obtained by using HVSR method utilizing different softwares. Furthermore, response spectra were obtained for
different local soil classes by using the data of the same stations and they are given in comparison with the design spectra included in
the earthquake code. As a result of the study, it has been observed that the results obtained by the HVSR method are in good correlation
with the soil effects in the region and the consequential structural damages. These examples illustrate HVSRpy’s commitment to exactly
reproduce the results of GEOPSY, wherever the processing parameters and functionality of HVSRpy and GEOPSY overlap. This was
done to allow users to check HVSRpy and to encourage standardization in HVSR processing.
Human activity causes vibrations that propagate into the ground as high-frequency seismic waves. Measures to mitigate the COVID-19 pandemic caused widespread changes in human activity, leading to a months-long reduction in seismic noise of up to 50%. The 2020 seismic noise quiet period is the longest and most prominent global anthropogenic seismic noise reduction on record. While the reduction is strongest at surface seismometers in populated areas, this seismic quiescence extends for many kilometers radially and hundreds of meters in depth. This provides an opportunity to detect subtle signals from subsurface seismic sources that would have been concealed in noisier times and to benchmark sources of anthropogenic noise. A strong correlation between seismic noise and independent measurements of human mobility suggests that seismology provides an absolute, real-time estimate of population dynamics.
In this study, time-dependent probabilistic tsunami hazard analysis (PTHA) is performed for Tuzla, Istanbul, in the Sea of Marmara, Turkey, using various earthquake scenarios of Prince Island Fault (PIF) within the next 50 and 100 years. The Monte Carlo (MC) simulation technique is used to generate a synthetic earthquake catalogue, which includes earthquakes having moment magnitudes between Mw6.5 and 7.1. This interval defines the minimum and maximum magnitudes for the fault in the case of an entire fault rupture, which depends on the characteristic fault model. Based on this catalogue, probability of occurrence and associated tsunami wave heights are calculated for each event. The study associates the probabilistic approach with tsunami numerical modeling. The tsunami numerical code NAMI DANCE was used for tsunami simulations. According to the results of the analysis, distribution of probability of occurrence corresponding to tsunami hydrodynamic parameters is represented. Maximum positive and negative wave amplitudes show that tsunami wave heights up to 1 m have 65 % probability of exceedance for the next 50 years and this value increases by 85 % in the Tuzla region for the next 100 years. Inundation depth also exceeds 1 m in the region with probabilities of occurrence of 60 % and 80 % for the next 50 and 100 years, respectively. Moreover, probabilistic inundation maps are generated to investigate inundated zones and the amount of water penetrated inland. Probability of exceedance of 0.3 m wave height ranges between 10 % and 75 % according to these probabilistic inundation maps, and the maximum inundation distance calculated in the entire earthquake catalogue is 60 m in this test site. Furthermore, synthetic gauge points are selected along the western coast of Istanbul by including Tuzla coasts. Tuzla is one of the areas that shows high probability exceedance of 0.3 m wave height, which is around 90 %, for the next 50 years while this probability reaches up to more than 95 % for the next 100 years.
We relocated the seismicity in SE Aegean that was recorded by both permanent and temporary seismic networks during 2004–2018 in order to investigate its correlation with the active faults in this area. P and S-phase travel times of best quality events were used to estimate a minimum 1D velocity model with station delays by utilizing VELEST. This velocity model and station delays were then used to obtain absolute locations of 3055 events, utilizing the probabilistic nonlinear algorithm NLLOC. The double-difference algorithm was used along with catalog and cross-correlation differential times to relocate all the events, resulting in 2200 precise relative locations with horizontal and vertical uncertainties of less than 1.0 km. The precise locations delineated faults along the Gulf of Gökova, SW of Nisyros, and Karpathos area. Based on the comparison of the resulting seismicity distribution with the regional stress field, it can be concluded that seismicity only occurred along faults with ENE-WSW strike in the area north of Tilos and N-S strike in the area south of Tilos. Seismogenic layer thickness estimated from the hypocentral depth distribution was found to vary between 12.1 and 15.4 km. Expected moment magnitudes of faults in this area were calculated by using their geometrical properties and the seismogenic layer thickness, yielding magnitudes in the range of 5.9–6.9. The fact that most of the seismically active faults in SE Aegean lie offshore increases the probability that a major earthquake will be followed by a tsunami and calls for the close monitoring of seismicity in this area.
KOERI has a long history of earthquake seismology,
beginning its observations right after the devastating earthquake on 10 July 1894 in Istanbul, by deploying the first seismograph in the region.
Naturally, its seismic network and earthquake catalog evolved since that
time, in harmony with the progress in the science of seismology. Currently,
the seismic network consists of 242 stations that record approximately 1500
earthquakes per month during periods of regular seismicity. Magnitude is one
of the most critical parameters in determining the size of an earthquake,
especially in seismic hazard assessment studies. The objective of this study
is to homogenize the magnitudes of the KOERI catalog between 2008 and 2018.
For this aim, we computed the Magnitude of Completeness (Mc) for two
different time periods between 2008–2011 and 2012–2018 by taking into
account the duration magnitude (Md) and local magnitude (Ml), where these
parameters might not be available jointly for the both time periods
considered. As a result, we present a relationship of Md and Ml magnitudes
derived from and applicable to KOERI's earthquake catalogs.
This article describes the Engineering Strong-Motion Database (ESM), developed in the framework of the European project Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation (NERA, see Data and Resources). ESM is specifically designed to provide end users only with quality-checked, uniformly processed strong-motion data and relevant parameters and has done so since 1969 in the Euro-Mediterranean region. The database was designed for a large variety of stakeholders (expert seismologists, earthquake engineers , students, and professionals) with a user-friendly and straightforward web interface. Users can access earthquake and station information and download waveforms of events with magnitude ≥ 4:0 (unproc-essed and processed acceleration, velocity, and displacement, and acceleration and displacement response spectra at 5% damping). Specific tools are also available to users to process strong-motion data and select ground-motion suites for code-based seismic structural analyses.
Archival and near-real-time access to instrumented sites and structures through the European Integrated waveform Data Archive (EIDA), Rapid Raw Strong-Motion Database (RRSM) and Station Book. ABSTRACT We present the European Integrated Data Archive (EIDA), which can provide data archival and near-real-time dissemination of waveforms collected by European data centers from instrumented sites and structures. Current EIDA nodes are European institutions collecting and archiving data from seismic networks deploying broadband sensors, short-period sensors and strong-motion accelerometers. EIDA presently delivers seismic data from ~ 5000 stations from ~140 networks. All EIDA data is used to generate the European Rapid Raw Strong-Motion Database (RRSM) which provides earthquake information and engineering parameters within minutes of any event with magnitude > 3.5 in the greater European region. EIDA information is also included in a station book that comprises critical site characterisation parameters, including basic description of instrumented sites. As services in the European Plate Observing System (EPOS) EIDA, the RRSM and the station book are expected to be the long-term solutions for European dissemination of data from instrumented sites and structures.
Online material: Complete list of earthquakes used in this study.
Three-component ground-motion recordings are critical to modern seismic analysis techniques such as receiver functions and body- and surface-wave polarization studies. Modern three-component seismometers typically resolve three axes of ground motion into one vertical and two orthogonal horizontal directions. The standard convention for installation is to orient the instrument such that one of the horizontal components is aligned with true north, taking into account the current local magnetic declination at the station. This practice can be difficult in the case of borehole instruments and practically impossible for ocean-bottom seismometers (OBS). Some deployments of OBS have used airgun shots to determine sensor orientation (Anderson et al. , 1987; Duennebier et al. , 1987); however, this is not an error- or cost-free procedure and is not always available. In these cases, determination of sensor orientation is necessary independent of human interaction with the physical instrument. The elliptical particle motion of Rayleigh waves is exploited here to calculate sensor orientation based on the statistical analysis of earthquakes recorded on OBS deployed around the south island of New Zealand. This robust method is computationally fast because synthetic seismograms are not generated and accurate source parameters are not necessary. The technique is compared with body-wave orientation results and full-waveform surface-wave orientation results. Application of this method to waveforms recorded on land stations and synthetic waveforms confirms its reliability.
Surface-wave arrival azimuth is determined via polarization analysis of the Rayleigh wave recorded on a three-component sensor. Rayleigh waves exhibit retrograde elliptical particle motion, theoretically only observed on the vertical and radial components. Because it is more stable to quickly determine a linear relationship than to measure ellipticity, the polarization analysis is performed by cross correlating the vertical component with the Hilbert-transformed radial component. The 90° phase …
ObsPy: The Python toolbox for seismology (http://www.obspy.org) aims at filling the gap between interactive analysis and automatic data acquisition systems. Automatic batch analysis of continuous data streams or feeding a so far unknown formatted data stream into an acquisition system are two possible applications.
We present a new approach to characterize the background seismic noise across the continental United States. Using this approach, power spectral den-sity (PSD) is estimated at broadband seismic stations for frequencies ranging from 0.01 to 16 Hz. We selected a large number of 1-hr waveform segments during a 3-yr period, from 2001 to 2003, from continuous data collected by the U.S. National Seismograph Network and the Advanced National Seismic System (ANSS). For each segment of continuous data, the PSD is estimated and smoothed in full-octave averages at 1/8 octave intervals. Powers for each 1/8 period interval were then accumulated in 1-dB power bins. A statistical analysis of power bins yields probability density functions (PDFs) as a function of noise power for each of the octave bands at each station and component. There is no need to account for earth-quakes since they map into a background probability level. A comparison of day and night PDFs and an examination of artifacts related to station operation and episodic cultural noise allow us to estimate both the overall station quality and the level of earth noise at each site. Percentage points of the PDFs have been derived to form the basis for noise maps of the contiguous United States at body-wave frequencies. The results of our noise analysis are useful for characterizing the performance of existing broadband stations and for detecting operational problems and should be relevant to the future siting of ANSS backbone stations. The noise maps at body-wave frequencies should be useful for estimating the magnitude threshold for the ANSS backbone and regional networks or conversely for optimizing the distribution of regional network stations.
The correct orientation of seismic sensors is critical for studies such as full moment tensor inversion, receiver function analysis, and shear‐wave splitting. Therefore, the orientation of horizontal components needs to be checked and verified systematically. This study relies on two different waveform‐based approaches, to assess the sensor orientations of the broadband network of the Kandilli Observatory and Earthquake Research Institute (KOERI). The network is an important backbone for seismological research in the Eastern Mediterranean Region and provides a comprehensive seismic data set for the North Anatolian fault. In recent years, this region became a worldwide field laboratory for continental transform faults. A systematic survey of the sensor orientations of the entire network, as presented here, facilitates related seismic studies. We apply two independent orientation tests, based on the polarization of P waves and Rayleigh waves to 123 broadband seismic stations, covering a period of 15 yr (2004–2018). For 114 stations, we obtain stable results with both methods. Approximately, 80% of the results agree with each other within 10°. Both methods indicate that about 40% of the stations are misoriented by more than 10°. Among these, 20 stations are misoriented by more than 20°. We observe temporal changes of sensor orientation that coincide with maintenance work or instrument replacement. We provide time‐dependent sensor misorientation correction values for the KOERI network in the supplemental material.
Human activity is a major source of high-frequency seismic noise. Long-term ambient seismic noise levels and their influencing factors are investigated. The diurnal seismic noise level in 5–15 Hz display high correlation with human activities including traffic and industrial operations that are related to economic conditions. The temporal noise-level variations are consistent among three components. Analysis with seismic noises in three consecutive months of each year enables us to estimate the noise levels without seasonal effects. The daytime seismic noise-level changes in major cities of 11 countries are assessed using the 3 month records for decades. The annual seismic noise levels present strong correlations with gross domestic product (GDP), particularly with manufacturing and industrial GDP. The seismic noise levels increase quickly with GDP in low-GDP regions but slowly in high-GDP regions. This is because high-GDP regions already have large volumes of existing noise-inducing sources and because added sources contribute weakly. The seismic noise levels increased by 14%–111% for 5–23 yr depending on the economic conditions. The correlation between ambient seismic noise level and economy growth is a global feature. The high-frequency noise level may be a proxy to present the economic condition. Economic growth affects the Earth environment in a wide range of aspects.
Modular Utility for STatistical kNowledge Gathering (MUSTANG) is a data quality assurance resource that scientists and network operators can use to assess the quality of seismic data archived at the Incorporated Research Institutions for Seismology (IRIS) Data Management Center. It is a system for automated calculation of metrics on seismic waveforms and distribution of these metrics via web services. Measurements span the entirety of the archive and are updated as needed when data or metadata change. MUSTANG precalculates and stores most metrics in a database, but a select few are dynamically generated when a web service request is made. Users can access metrics through the web service interfaces and also through easy-to-use client tools. This article describes the creation and construction of MUSTANG, as well as current and envisioned uses of its data quality measurements.
We present the European Rapid Raw Strong‐Motion database (RRSM), a new Europe‐wide system that provides parameterized earthquake ground‐motion information, as well as access to waveform data, within minutes of the occurrence of any earthquake with M≥3.5 occurring in the European–Mediterranean region. The RRSM is different from traditional platforms for disseminating earthquake strong‐motion data in Europe, which focus on providing reviewed, processed strong‐motion parameters, typically with significant delays. The RRSM provides rapid open access to raw waveform data and metadata and does not rely on manual waveform processing. The RRSM targets seismologists and strong‐motion data analysts, earthquake and geotechnical engineers, international earthquake response agencies, and the educated general public. The database is accessible online (see Data and Resources). Users can query earthquake information, peak ground‐motion parameters, and select and download earthquake waveforms. The RRSM database is populated using the waveform processing module scwfparam, which is integrated in SeisComP3. Processing is triggered using earthquake parameters provided by the European–Mediterranean Seismological Center and uses all significant waveform data that are available in the European Integrated waveform Data Archive (EIDA). EIDA consists of broadband and strong‐motion data from across Europe, and the majority of these data are available in near real time. All relevant, on‐scale open EIDA data are processed for the RRSM. As the EIDA community is continually growing, the already significant number of strong‐motion stations is also increasing and the importance of the RRSM database is expected to grow further in time. Real‐time RRSM processing started in September 2014, whereas offline reprocessing was carried out for all M4.5+ events that occurred since January 2005.
Online Material: Tables of station orientations and earthquake catalog, and figures showing comparison of synthetic and observed waveforms.
The orientation of seismic instruments relative to north is a critical parameter in many seismological applications. Three‐dimensional studies of surface‐wave dispersion depend on accurate seismic sensor orientation (Ekstrom et al. , 1997). This parameter is also important in the study of off‐great‐circle propagation of long‐period surface waves (Laske, 1995), as well as in estimates of the anisotropic structure of the mantle using SKS splitting observations (Long et al. , 2009). Finally, sensor orientation is critical in the comparison of observed and synthetic records in seismic source studies. In a recent study of southern Iberia and the influence of the moment tensor resolvability, Zahradnik and Custodio (2012) found that a 10° sensor misorientation induces data errors that vary between 10% and 40% of the amplitude of the original waveform; for a station with a 30° misorientation, the original waveform will thus have an error between 30% and 90%. These are just a few examples from seismic research showing the great influence that correct orientation exerts on a seismic station’s horizontal components.
Several factors act as sources of misorientation. First, in many seismic networks, such as the Spanish Broadband National Network (SBNN), most of the seismometers are installed in abandoned mines or natural caves that have no direct line of sight to any external point of reference. An overall precision of ±1° has been reached using precise magnetic orientation; however, this is not possible in locations where magnetic material is present. Often, reorientations are not performed during reinstallations, maintenance visits, or seismometer changes. There is no information available or recorded regarding operational routing; in other words, there is no obtainable log of possible relocations of seismometer. Second, the orientation obtained at the entrance to the site …
Generic Mapping Tools (GMT) is an open-source software package for the analysis and display of geoscience data, helping scientists to analyze, interpolate, filter, manipulate, project, and plot time series and gridded data sets. The GMT toolbox includes about 80 core and 40 supplemental program modules sharing a common set of command options, file structures, and documentation. Its power to process data and produce publication-quality graphic presentations has made it vital to a large scientific community that now includes more than 25,000 individual users. GMT's website (http://gmt.soest.hawaii.edu/) exceeds 20,000 visits per month, and server logs show roughly 2000 monthly downloads.
Horizontal seismic data are utilized in a large number of Earth studies. Such work depends on the published orientations of the sensitive axes of seismic sensors relative to true North. These orientations can be estimated using a number of different techniques: SensOrLoc (Sensitivity, Orientation and Location), comparison to synthetics (Ekstrom and Busby, 2008), or by way of magnetic compass. Current methods for finding relative station azimuths are unable to do so with arbitrary precision quickly because of limitations in the algorithms (e.g. grid search methods). Furthermore, in order to determine instrument orientations during station visits, it is critical that any analysis software be easily run on a large number of different computer platforms and the results be obtained quickly while on site.We developed a new technique for estimating relative sensor azimuths by inverting for the orientation with the maximum correlation to a reference instrument, using a non-linear parameter estimation routine. By making use of overlapping windows, we are able to make multiple azimuth estimates, which helps to identify the confidence of our azimuth estimate, even when the signal-to-noise ratio (SNR) is low. Finally, our algorithm has been written as a stand-alone, platform independent, Java software package with a graphical user interface for reading and selecting data segments to be analyzed.
Modern broadband seismometers generally have well-known and stable instrument parameters. Typically, the manufacturer's specifications indicate that the gain of each component of a three-component seismometer is known to within 1% and that the orthogonality of the components is true to within a fraction of a degree. Such precision makes possible many types of quantitative seismological analyses that were difficult with earlier instruments. In particular, different components of earlier three-component seismometers did not necessarily have the same response functions ( e.g. , free period of the seismometer), making any analysis based on the rotation of ground motion into the transverse and longitudinal directions difficult. Such technical problems have now largely been overcome in the most common broadband instrumentation, and it is routine to perform rotational transformations of the horizontal components of motion in modern seismological analyses, such as earthquake source investigations, S and SKS splitting studies, receiver-function determinations, and body- and surface-wave-polarization studies.
An essential station variable for the rotational transformation of horizontal components of motion is the geographical orientation of the original components in the horizontal plane. Horizontal seismometers are typically installed with output sensitivity aligned to the north-south and east-west directions, and the standard names of seismometer channels ( e.g. , BHN, BHE) reflect this convention. Nontraditional orientations are common for borehole and ocean-bottom seismometers, for which it is cumbersome or impossible to install the seismometer with a specified orientation, and the orientation is instead determined after deployment. In general, instruments with nontraditional orientations have channel names that reflect this ( e.g. , BH1, BH2). Regardless of how the seismometer is oriented at installation, the azimuths of sensitivity of the horizontal components are subsequently distributed as auxiliary data. In the SEED convention, as well as in other data distribution formats, the precision of this parameter is given to at least 0.1°.
Despite …
A new method for measuring arrival angles of teleseismic Love and Rayleigh waves is developed. The new method utilizes estimates of surface wave dispersion to create a phase-matched filter to isolate the Love or Rayleigh wave in three-component recordings. The polarization of the filtered wave group is determined in the time domain by application of a variation of the complex polarization method of Vidale [1986]. Orientation, linearity, and ellipticity of particle motion are estimated in several frequency bands to determine the frequency-dependent polarization. The method employs an iterative scheme, by which a predicted Love wave, based on the estimated dispersion and polarization, is subtracted from the three-component data prior to the estimation of Rayleigh wave polarization, and vice versa. The method is applied to an extensive set of Global Seismographic Network data covering the years 1989-1998. Between 4244 and 15,075 measurements are collected for fundamental mode Love and Rayleigh waves at nine different periods (37 to 150 s). Measurement uncertainties are estimated using the statistics of observations for pairwise similar paths and are generally of the order of 15-50% of the total signal, depending on the period and the wave type. Large and azimuthally invariant angle anomalies are documented for several stations and are consistent with misorientation of the horizontal seismometers. Two schemes are employed to determine the misorientations: (1) an azimuthally weighted average at each station, and (2) a joint inversion for seismometer misorientation and globally heterogeneous phase velocities. The determined corrections are robust and correlate well with those reported in earlier studies. Azimuthally varying arrival angle anomalies are shown to agree qualitatively with predictions of wave refraction calculated for recent phase velocity maps, which explain up to 30% of the variance in the new measurements.
Tsunami mitigation, preparedness and early warning initiatives have begun at the global scale only after the tragic event of Sumatra in 2004. Turkey, as a country with a history of devastating earthquakes, has been also affected by tsunamis in its past. In this paper we present the Tsunami Hazard in the Eastern Mediterranean and its connected seas (Aegean, Marmara and Black Sea) by providing detailed information on historically and instrumentally recorded significant tsunamigenic events surrounding Turkey, aiming to a better understanding of the Tsunami threat to the Turkish coasts. In addition to the review of the Tsunami hazard, we have studied a possible Tsunami source area between Rhodes and SW of Turkey using Tsunami numerical model NAMI DANCE-two nested domains. We have computed a maximum positive amplitude of 1.13 m and maximum negative amplitude of −0.5 m at the Tsunami source by this study. The distribution of maximum positive amplitudes of the water surface elevations in the selected Tsunami forecast area and time histories of water level fluctuations near selected locations (Marmaris, Dalaman, Fethiye and Kas towns) indicate that the maximum positive amplitude near the coast in the selected forecast area exceeds 3.5 m. The arrival time of maximum wave to Marmaris, Dalaman, is 10 min, while that of Fethiye and Kas towns is 15–20 min. The maximum positive amplitudes near the shallow region of around 10 m depth are 3 m (Marmaris), 1 m (Dalaman), 2 m (Fethiye) and 1 m (Kas). Maximum positive amplitudes of water elevations in the duration of 4 h simulation of the Santorini-Minoan Tsunami in around 1600 BC in the Aegean Sea are also calculated based on a simulation performed using 900 m grid resolution of Aegean sea bathymetry with a 300 m collapse of 10 km diameter of Thera (Santorini) caldera. We have also presented the results of the Tsunami modeling and simulation for Marmara Sea obtained from a previous study. Last part of this paper provides information on the establishment of a Tsunami Warning Center by KOERI, which is expected to act also as a regional center under the UNESCO Intergovernmental Oceanographic Commission – Intergovernmental Coordination Group for the Tsunami Early Warning and Mitigation System in the North-Eastern Atlantic, the Mediterranean and Connected Seas (ICG/NEAMTWS) initiative, emphasizing on the challenges together with the future work needed to be accomplished.
EIDA: The European Integrated Data Archive and service infrastructure within ORFEUS
- G Lanzano
- L Luzi
- C Cauzzi
- J Bienkowski
- D Bindi
- J Clinton
- M Cocco
- M D'amico
- J Douglas
- L Faenza
last accessed in January 2021. The other information is from
the unpublished manuscript by G. Lanzano, L. Luzi, C. Cauzzi, J.
Bienkowski, D. Bindi, J. Clinton, M. Cocco, M. D'Amico, J.
Douglas, L. Faenza, et al., 2021, "Accessing European Strong-Motion Data: An update on ORFEUS coordinated services",
Seismol. Res. Lett. and from the unpublished manuscript by A.
Strollo, D. Cambaz, J. Clinton, P. Danecek, C. P. Evangelidis, A.
Marmureanu, L. Ottemöller, H. Pedersen, R. Sleeman, K.
Stammler, et al., 2021, "EIDA: The European Integrated Data
Archive and service infrastructure within ORFEUS."
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