Geodetic Investigation of the 30 October 2020 Mw 6.9 Samos-Izmir Earthquake

<p>The earthquake with a magnitude of Mw 6.9 (according to Kandilli Observatory and Earthquake Research Institute-KOERI) occurred 8 km north of Samos Island at a depth of 16 km, on 30.10.2020, at 11:51:24 UTC. It took place on the north-dipping normal fault zone of approximately 40 km length in the sea between Samos Island of Greece and Kuşadası Bay of Turkey. After the mainshock, a tsunami with the height exceeding 1 meter occurred in Seferihisar region, south of Izmir, and north side of Samos Island. In this study, a geodetic investigation of the Samos-Izmir earthquake using GNSS and SAR techniques was carried out. Within the scope of this study, 1Hz observations of Turkey National Continuous GNSS Network-Active (TUSAGA-Aktif) stations in the earthquake zone, were used, and it was aimed to reveal the co-seismic deformation caused by the earthquake. In addition to GNSS data, the InSAR process has been performed by using ESA Sentinel-1 SAR data, and the vertical deformations were clarified with the unwrapped interferogram. The GNSS data were processed using web-based online processing services according to the relative and absolute positioning techniques as static and kinematic modes. In conclusion, considering the absolute and relative static processing of pre- and post-earthquake GNSS data, the maximum horizontal deformations were observed at CESM and IZMI GNSS stations located in the north of the fault. Due to the earthquake, these points moved to the north direction and the maximum horizontal deformations were found as 5.5 cm and 3.5 cm, respectively. According to the kinematic processing of the GNSS data, instantaneous horizontal movements of 12 cm and 4 cm towards the north were observed at the same stations, respectively, at the time of the earthquake. On the contrary, DIDI and AYD1 GNSS stations, which are located in the south of the fault, moved to the south-east direction and the magnitude of horizontal deformations were smaller. Considering the InSAR results, it was seen a 10 cm uplift in the west of the island of Samos and a 10 cm subsidence at the northernmost part. Besides this, a 5 cm subsidence was observed in Izmir territory, the north side of the fault, by means of the interferogram.</p>

Evolution of the Kandilli Observatory and Earthquake Research Institute (KOERI) Seismic Network and the Data Center Facilities as a Primary Node of EIDA

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.

SEPTEMBER 26, 2019 Mw5.8 MARMARA SEA-SILIVRI (ISTANBUL) EARTHQUAKE: ANALYSIS OF GROUND MOTION RECORDS

<p>Marmara region located on the western end of the North Anatolian Fault Zone is a tectonically active region in Turkey. There have been frequent severe earthquakes in the region and will continue to occur. There was no serious earthquake in the region after the 1999 Mw7.4 Kocaeli and Mw7.2 Düzce earthquakes. A Marmara Sea offshore earthquake Mw5.8 close to Silivri Town of Istanbul Metropolitan City has occurred on September 26, 2019 daytime at 13:59. The earthquake happened at the coordinate of 40.87N – 28.19E with a depth of 7.0km on the Kumburgaz segment of the North Anatolian Fault line. It was felt in almost all Marmara region. In some settlements in Istanbul City, slight to moderate damages were observed. A foreshock earthquake of Mw4.8 occurred on the same segment on 24 September, 2019. 150 aftershock events ranging from M1.0 to M4.1 have been recorded within the 24 hours after the mainshock. The ground motions have been recorded in the region by the several institutions including AFAD (Disaster and Emergency Management Presidency), KOERI (Kandilli Observatory and Earthquake Research Institute) and IGDAS (Istanbul Gas Distribution Industry and Trade Inc.). The ground motion records and selected parameters have been examined in this study. The ground motion parameters (MMI, PGA, PGV, Sa, Sv, Sd) distribution have been achieved and checked by the recent NGA-West2 ground motion prediction equations (GMPEs); ASK2014, CY2014 and BSSA2014. The compatibility of the GMPEs for a moderate size Marmara Sea earthquake has been examined.</p>

A conceptual model to increase the visibility and usage of cultural heritage objects: The case of UNESCO’s Memory of the World list1

Cultural heritage connects the past with the future by forming an integral part of the identities of societies. Thus, countries must protect their cultural heritage and create policies to ensure that people benefit today and pass the heritage on to future generations. Beyond physical protection in the face of globalization, increasing access to cultural heritage is necessary to ensure participation and evaluate practices from an international perspective. Advances in computer and communication technologies are being exploited for these requirements. Acquiring knowledge about and interacting with cultural objects in any part of the world today is possible through the digital humanities approach. In this study, a conceptual model was formed to increase visibility and usage of Kandilli Observatory and Earthquake Research Institute Manuscripts, the Hittite cuneiform tablets from Bogazköy, the works of Ibn Sina at the Süleymaniye Manuscript Library, Evliya Çelebi’s ‘Book of Travels’, and the Old Assyrian Merchant Archives of Kültepe registered in UNESCO’s Memory of the World List. In this model, which is prepared with the digital humanities approach, best practices applied in the field are considered as examples in the literature. Suggestions are made on how to utilize digital humanities tools to increase access and visibility by revealing the economic, social, and cultural values of the works based on the model.

Analog Seismogram Archives at the Earthquake Research Institute, the University of Tokyo

The Earthquake Research Institute (ERI) of the University of Tokyo maintains archives of analog seismograms and mareograms. The main collection is ∼236,000 Japanese historical seismograms recorded at the University of Tokyo (at various buildings and using various instruments around Hongo [Tokyo] with a total of 189,000 records from 1881 to 1993), at the Tsukuba observatory (∼11,000 records from 1921 to 1986), and at the Wakayama seismological network (∼12,650 records from 1928 to 1968). Seismograms recorded by temporal stations at various locations in Japan for several years, typically following large earthquakes, are also included. Different types of instruments were used to record the data. The oldest record from a large earthquake is from the 1891 Nobi earthquake recorded at Hongo on a circular seismogram using an Ewing-type seismograph. Teleseismic seismograms include those from the 1899 Alaska earthquake at Hongo on an Omori-type seismograph. Imamura-type and Omori-type tremometers and strong-motion seismographs had also been used for a long time. While these seismograms were microfilmed by the 1990s, the original smoked paper records have also been archived. Foreign seismogram collections include those from earthquakes in Taiwan between 1904 and 1917 recorded in both Japan and Taiwan and those from the Canadian Seismograph Network between 1981 and 1989. For the Worldwide Standardized Seismograph Network stations, almost all (∼5,000,000) microfilm records at 167 stations from 1963 to 1988 are archived. High-resolution image scanning of analog daily seismograms at the Wakayama microearthquake network is currently being performed, and the scans are provided using Leaflet software so that the users can easily access and enlarge parts of seismograms. The tsunami waveform archive contains ∼3100 records on Japanese tide gauges from large earthquakes between 1911 and 1996. The available data, with dates and types of instruments, can be searched from the database through the website of the ERI.

A Review on Kandilli Observatory and Earthquake Research Institute (KOERI) Seismic Network and Earthquake Catalog: 2008–2018

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.

New constraints on the 1922 Atacama, Chile, earthquake from Historical seismograms

SUMMARY We recently found the original Omori seismograms recorded at Hongo, Tokyo, of the 1922 Atacama, Chile, earthquake (MS = 8.3) in the historical seismogram archive of the Earthquake Research Institute (ERI) of the University of Tokyo. These recordings enable a quantitative investigation of long-period seismic radiation from the 1922 earthquake. We document and provide interpretation of these seismograms together with a few other seismograms from Mizusawa, Japan, Uppsala, Sweden, Strasbourg, France, Zi-ka-wei, China and De Bilt, Netherlands. The 1922 event is of significant historical interest concerning the cause of tsunami, discovery of G wave, and study of various seismic phase and first-motion data. Also, because of its spatial proximity to the 1943, 1995 and 2015 great earthquakes in Chile, the 1922 event provides useful information on similarity and variability of great earthquakes on a subduction-zone boundary. The 1922 source region, having previously ruptured in 1796 and 1819, is considered to have significant seismic hazard. The focus of this paper is to document the 1922 seismograms so that they can be used for further seismological studies on global subduction zones. Since the instrument constants of the Omori seismographs were only incompletely documented, we estimate them using the waveforms of the observed records, a calibration pulse recorded on the seismogram and the waveforms of better calibrated Uppsala Wiechert seismograms. Comparison of the Hongo Omori seismograms with those of the 1995 Antofagasta, Chile, earthquake (Mw = 8.0) and the 2015 Illapel, Chile, earthquake (Mw = 8.3) suggests that the 1922 event is similar to the 1995 and 2015 events in mechanism (i.e. on the plate boundary megathrust) and rupture characteristics (i.e. not a tsunami earthquake) with Mw = 8.6 ± 0.25. However, the initial fine scale rupture process varies significantly from event to event. The G1 and G2, and R1 and R2 of the 1922 event are comparable in amplitude, suggesting a bilateral rupture, which is uncommon for large megathrust earthquakes.

“Urban Resilience” for Mega Earthquake Disasters Part 2

Based on the lessons from the 2011 Great East Japan Earthquake Disaster, the Ministry of Education, Culture, Sports, Science and Technology has launched “Special Project for Reducing Vulnerability for Urban Mega Earthquake Disasters (2012–2016)” with the aim of reducing the damages caused by the urban earthquake disasters such as the projected earthquake that directly hits Tokyo area and the Tokai, Tonankai and Nankai Earthquakes as much as possible. This project is divided into the following three subprojects: namely, 1) “Research and Study on Evaluation of Risk and Hazard of Earthquake that Directly Hits Tokyo Area” represented by Professor Naoshi Hirata, Earthquake Research Institute, the University of Tokyo; 2) “Research and Study on Maintenance and Recovery of Functionality in Urban Infrastructures” represented by Professor Masayoshi Nakashima, Disaster Prevention Research Institute, Kyoto University; and 3) “Research and Study on Measures to Improve Urban Resilience to Earthquake Disaster” represented by Dr. Haruo Hayashi, President of the National Research Institute for Earth Science and Disaster Resilience. This special issue focuses on the findings of the subproject 3). The subproject 3) aims to develop the information communication system for supporting efficient management of emergency responses and restoration efforts and promotion of the capabilities for solution of the problems in terms of disaster, i.e. disaster management literacy, to contribute to high resilience to disaster in our society.

Shear wave splitting as a proxy for stress forecast of the case of the 2006 Manyas-Kus Golu (<i>M</i>_b = 5.3) earthquake

The 2006 Mb = 5.3 Manyas-Kus Golu (Manyas) earthquake has been retrospectively "stress-forecasted" using variations in time-delays of seismic shear wave splitting to evaluate the time and magnitude at which stress-modified microcracking reaches fracture criticality within the stressed volume where strain is released. We processed micro earthquakes recorded by 29 TURDEP (Multi-Disciplinary Earthquake Research in High Risk Regions of Turkey) and 33 KOERI (Kandilli Observatory and Earthquake Research Institute) stations in the Marmara region by using the aspect-ratio cross-correlation and systematic analysis of crustal anisotropy methods. The aim of the analysis is to determine changes in delay-times, hence changes in stress, before and after the 2006 Manyas earthquake. We observed that clear decreases in delay times before the impending event, especially at the station GEMT are consistent with the anisotropic poro-elasticity (APE) model of fluid-rock deformation, but we could not observe similar changes at other stations surrounding the main event. The logarithms of the duration of the stress-accumulation are proportional (self-similar) to the magnitude of the impending event. Although time and magnitude of th 2005 Manyas earthquake could have been stress-forecasted, as has been recognized elsewhere, shear-wave splitting does not appear to provide direct information about the location of impending earthquakes.

Ground motion predictive modelling based on genetic algorithms

This study aims to utilise genetic algorithms for the estimation of peak ground accelerations (PGA). A case study is carried out for the earthquake data from south-west Turkey. The input parameters used for the development of attenuation relationship are magnitude, depth of earthquake, epicentral distance, average shear wave velocity and slope height of the site. Earthquake database compiled by the Earthquake Research Institute of Turkey was used for model development. An important contribution to this study is the slope/hill data included into the dataset. Developed empirical model has a good correlation (R = 0.78 and 0.75 for the training and overall datasets) between measured and estimated PGA values. The proposed model is also compared with local empirical predictive models and its results are found to be reasonable. The slope-hill effect found to be an important parameter for the estimation of PGA.