• Earthquakes and Structures
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• v.17 no.4
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• pp.355-363
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• 2019

Masonry structures in the rural areas of Turkey often damaged due to moderate and big earthquakes. After every earthquake many scientists made field investigations on the earthquake performance of these structures and gave many useful information on construction techniques. However, the newly constructed masonry buildings are still not suitable for the suggested techniques, and they are still in danger against future earthquakes. Five moderate earthquakes of moment magnitude Mw 5.3, 5.3, 5.2, 5.0, and 5.3 struck the Ayvacik-Çanakkale District of Turkey between 6 and 12 February, 2017. More than a thousand of aftershocks were occurred and most of the masonry buildings in the villages nearby main shock epicenter were affected. The author went to the earthquake field and investigated the earthquake performances of masonry structures. This paper presents the recorded acceleration data, acceleration response spectra, and the seismological aspects of these earthquakes. Besides, case studies of damaged stone masonry buildings, and failure mechanisms are discussed with illustrated photos which were taken during the field investigations. It is concluded that the damaged masonry buildings were not designed and constructed properly in accordance with the Turkish building codes or similar specifications.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.44-48
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• 2000

Several parameters to represent the characteristics of the observed at the domestic networks from several earthquakes occurred in the Korean Peninsula. Parameters to fit most the multiple Fourier amplitude spectra of the observed accelerations are estimated. This study adopts the stochastic ground motion model referred to the BLWN mode in which the energy is distributed randomly over the duration of the source and which has proven to be very effective in modeling a wide range of ground motion observations. The stochastic ground motion model employed here uses an omega-squared ({{{{ omega ^2 }}) Brune source model with a single corner frequency and a constant stress drop,. The {{{{ omega ^2 }} source model has become a seismological standard because of its simplicity an ability to predict spectral amplitudes and shapes over an extremely broad ranges of magnitudes distances and from the inversion show very unstable based on the fact of high values of mean/median. These results may imply that more observed data and more precise site classification including accurate preparation analysis of data such as more accurate scaling from counts to kine are needed for more stable are effective inversion of Fourier amplitude spectrum of the observed ground motions.

• Proceedings of the KSEG Conference
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• 2005.04a
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• pp.107-110
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• 2005

The seismological observation of Korea began in 1905, and has been run with continuous earthquake network of observation, expanding to the advanced country, but still has some problems in accuracy and speed for report. There are many problems to issue the early warning system for earthquakes and Tsunami in the East Sea because most events in the East Sea occur outside the seismic network. Therefore multi-waveform data conversion and composition from the surrounding countries such as Korea, Japan and Far East Russia are requested in order to more accurate determination of earthquake parameters. We used FESNET(Far East Seismic Network) technology to analyze 2004 May 29th Uljin Earthquake and 2005 March 20th Japanese Fukuoka Earthquake in this research, using the data of KMA, Japan stations and IRIS(4 station).

• The Journal of Engineering Geology
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• v.5 no.3
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• pp.309-329
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• 1995

Seismicity and stress state in the Korean peninsula are studied using the catalogue of historical earthquakes and that from the seismological observations before the 1960s, with the aid of instrumental catalogue up to 1995. It seems that the completeness of the historical catalogue has a significant enhancement during the first two hundred years of the Yi dynasty, i.e., from the 1400s to the 1600s. From then on the catalogue may be regarded as near to complete for strong earthquakes in an overall sense. From the distribution of strong earthquakes, three seismic zones may be identified. From the south to the north, those are the southern seismic zone (남부지진대), the Seoul-Pyongyang seismic zone (서울-평양지진대), and the northern seismic zone (북부지진대). The mechanisms of some earthquakes obtained using first motion read- ings are reevaluated with a grid testing method. The results indicate that the compressional axis is nearly horizontal along the EW direction.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.341-363
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• 2012

The spectral representation method is a quick and versatile tool for the generation of spatially variable, response-spectrum-compatible simulations to be used in the nonlinear seismic response evaluation of extended structures, such as bridges. However, just as recorded data, these simulated accelerations require processing, but, unlike recorded data, the reasons for their processing are purely numerical. Hence, the criteria for the processing of acceleration simulations need to be tied to the effect of processing on the structural response. This paper presents a framework for processing acceleration simulations that is based on seismological approaches for processing recorded data, but establishes the corner frequency of the high-pass filter by minimizing the effect of processing on the response of the structural system, for the response evaluation of which the ground motions were generated. The proposed two-step criterion selects the filter corner frequency by considering both the dynamic and the pseudo-static response of the systems. First, it ensures that the linear/nonlinear dynamic structural response induced by the processed simulations captures the characteristics of the system's dynamic response caused by the unprocessed simulations, the frequency content of which is fully compatible with the target response spectrum. Second, it examines the adequacy of the selected estimate for the filter corner frequency by evaluating the pseudo-static response of the system subjected to spatially variable excitations. It is noted that the first step of this two-fold criterion suffices for the establishment of the corner frequency for the processing of acceleration time series generated at a single ground-surface location to be used in the seismic response evaluation of, e.g. a building structure. Furthermore, the concept also applies for the processing of acceleration time series generated by means of any approach that does not provide physical considerations for the selection of the corner frequency of the high-pass filter.

• The Journal of Engineering Geology
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• v.5 no.2
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• pp.181-192
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• 1995

The discrimination studies between earthquakes and underground nuclear explosions have been carried out by various seismologists(Nuttli and Kim, 1976; Dahiman and Israelson, 1977; Masse, 1981). The discrimination between local microearthquakes and artificial underground explosions(epicentral distance not greater than 400Km), however, has not been actively studied so far in the light of seismological aspects. Futhermore this kind of research has never been performed in Korea even if it is of great importance for IAEA (International Atomic Energy Agency) to clearly analyze the military nuclear power of North Korea at present. This research has been carried out by using some of the artificial underground explosions(about 100 events) have occurred in North Korea for the last six years. The azimuths, apparent incidence angles, epicentral distances and locations are determined using a single station of 3 - component data. The detection, location and identification are performed through the polarization and the bandpass filtering. This technique can be also applied to study the inhomogeneous crustal structure finding the converted waves.

• The Journal of Engineering Geology
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• v.16 no.2 s.48
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• pp.171-178
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• 2006

The seismological observation of Korea began in 1905, and has been run with continuous earthquake network of observation, expanding to the advanced country, but still has some problems in accuracy and speed for report. There are many problems to announce the early warning system for earthquakes and tsunami in the East Sea because most events in the East Sea occur outside the seismic network. Therefore multi-waveform data conversion and composition from the surrounding countries such as Korea, Japan and Far East Russia are requested in order to improve more accurate determination of the earthquake parameters. We used FESNET(Far East Seismic Network) technology to analyze the May 29 and June 1 Earthquakes, and the March 20, 2005 Fukuoka Earthquake in this research, using the data sets of KMA, Japan(JMA/MIED) and IRIS stations. It was found out that use of FESNET resulted in more better outputs than that of a single network, either KMA or JMA stations.

• Geophysics and Geophysical Exploration
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• v.12 no.4
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• pp.316-327
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• 2009

A standard for national seismological observatory was proposed on 1999. Since then, Quanterra digitizer has been installed and is operating on almost all of seismic stations which belong to major seismic monitoring organizations. Quanterra digitizer produce and transmit real-time event packet and data packet. Characteristics of event packet and arrival time of each channel's data packet on data center were investigated. Packet selection criteria using signal to noise ratio (hereafter SNR) and signal period from real-time event packet based on 100 samples per second (hereafter sps) velocity data were developed. Estimation of epicenter using time information of the selected event packet were performed and tested. A series of experiment show that event packets were received approximately 3~4 second earlier than data packets and the number of event packet was only 0.3% compare to data packets. Just about 5% against all of event packets were selected as event packet were related P wave of real earthquake. Using the selected event packets we can estimate an epicenter with misfit less than 10 km within 20 sec for local earthquake over magnitude 2.5.

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.37-46
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• 2005

In the field of earthquake engineering, recent improvements in many areas, such as seismological source modeling, analysis of travel path effects, and characterization of local site effects on strong shaking, have led to significant advances in both code-based and more advanced procedures for evaluating earthquake ground motions. A missing link, however, is empirically verified design procedures fur assessing the effects of soil-structure interaction (SSI). Available Soil-Structure Interaction (SSI) analysis techniques range from simple substructure-type procedures to relatively sophisticated finite element procedures. The most common substructure approach for foundation-soil interaction is to use a frequency-dependent and complex-valued impedance function. This study uniquely evaluates impedance functions for two well-instrumented sites w significant inertial SSI effects using a system Identification technique. The system identification analysis results are then compared to predictions from a simple theoretical model to gain insight into the inertial interaction effect in the subject sites.

• Structural Engineering and Mechanics
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• v.78 no.3
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• pp.351-368
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• 2021

This paper, by applying a reliability-based framework, develops seismic vulnerability macrozonation maps for Tehran, the capital and one of the most earthquake-vulnerable city of Iran. Seismic performance assessment of 3-, 4- and 5-story steel moment resisting frames (SMRFs), designed according to ASCE/SEI 41-17 and Iranian Code of Practice for Seismic Resistant Design of Buildings (2800 Standard), is investigated in terms of overall maximum inter-story drift ratio (MIDR) and unit repair cost ratio which is hereafter known as "damage ratio". To this end, Tehran city is first meshed into a network of 66 points to numerically locate low- to mid-rise SMRFs. Active faults around Tehran are next modeled explicitly. Two different combination of faults, based on available seismological data, are then developed to explore the impact of choosing a proper seismic scenario. In addition, soil effect is exclusively addressed. After building analytical models, reliability methods in combination with structure-specific probabilistic models are applied to predict demand and damage ratio of structures in a cost-effective paradigm. Due to capability of proposed methodology incorporating both aleatory and epistemic uncertainties explicitly, this framework which is centered on the regional demand and damage ratio estimation via structure-specific characteristics can efficiently pave the way for decision makers to find the most vulnerable area in a regional scale. This technical basis can also be adapted to any other structures which the demand and/or damage ratio prediction models are developed.