Journal of Japan Association for Earthquake Engineering
Online ISSN : 1884-6246
ISSN-L : 1884-6246
Volume 22, Issue 5
Displaying 1-4 of 4 articles from this issue
Technical Papers
  • Yoshiyuki KOMIYA, Kazuhiro HAYASHI, Hiroaki OSHIMA, Toshiki NAKAI, Tak ...
    2022 Volume 22 Issue 5 Pages 5_1-5_24
    Published: 2022
    Released on J-STAGE: November 30, 2022

    This paper proposes a method for calculating the maximum drift angle between seismometers using two seismometers installed on the first and upper floors of a building. With the wide-area expansion of the proposed method in mind, the seismometers aim to be able to evaluate even with the measurement accuracy of an accelerometer such as that built into a smartphone. Structural details about a building, time synchronization by the wired connection between two seismometers and a logger are not required. However, the seismometers must have a synchronization accuracy of time difference between the internal clocks by communication with NTP server, and must be corrected to the predetermined sampling frequency. An equivalent SDOF model estimates the response of a building. Primary natural angular frequency and damping ratio at the time of maximum response, which are unknown in the basic formula for calculating horizontal deformation between the seismometers, are solved from the peak of Fourier amplitude ratio obtained from acceleration records on the upper and lower floors. The features of this paper are to use elastic primary natural frequency evaluated at the end of the previous earthquake, and to narrow down primary natural frequency at the time of maximum response from a large number of peaks by dividing the acceleration records at regular intervals. The evaluation accuracy by the proposed method was verified using the results of four full-scale shaking table tests of S and RC structures carried out by E-Defense. As the results of the verification, it was confirmed that the measured values of the laser displacement gauge used in the tests and the evaluation results of the proposed method are almost consistent in the range from elastic region to plastic region. This verification is limited to the verification of a well-shaped building easily induced to primary mode, and the case where residual deformation and torsional deflection are small. Application to seismic motion where the principal motion continues for a long time, to buildings that are greatly affected by the soil-structure interaction effect, and to buildings of various shapes, as well as the solution of the maximum story drift angle, which is an important index for the damage degree of buildings, are out of the scope of this paper.

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  • Yoko MICHIGUCHI, Hideharu SUGINO, Yuta MITOBE, Hitoshi TANAKA
    2022 Volume 22 Issue 5 Pages 5_25-5_42
    Published: 2022
    Released on J-STAGE: November 30, 2022

    In order to evaluate the effects of horizontal crustal displacement on tsunami generation, the joint-inversion analysis and tsunami propagation analysis were conducted for the 2011 Tohoku earthquake tsunami using the method of Tanioka and Satake (1996), hereinafter referred to as the TS method, as well as a conventional one. We then compared the slip distributions evaluated by the two methods. In the entire tsunami source model, the slip area, average slip and the seismic moment with the TS method were about 90%, 90% and 84%, respectively, in comparison with those with the conventional one, and therefore, the effects of the method to consider horizontal crustal displacement were confirmed. While the average slip in the areas parallel to the trench axis with the TS method was highest in the area along the trench, the conventional method yielded the highest average slip values in a little deeper areas. The slip distribution by the TS method were reflected the actual phenomenon more in comparison with a conventional one.

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  • Masanobu TOHDO, Kensuke ARAI, Jun'ichi MIYAKOSHI, Toshiaki SATO, Hiroy ...
    2022 Volume 22 Issue 5 Pages 5_43-5_59
    Published: 2022
    Released on J-STAGE: November 30, 2022

    We re-examined the empirical scaling relationship between seismic moment M0 and short-period level A, which is the flat level of the acceleration source spectrum, adopted for setting asperity models of the inland crustal earthquakes in the “Recipe” for predicting strong ground motions published by the Headquarters for Earthquake Research Promotion (2020). Taking into consideration the scaling relationship between seismic moment and rupture area, which is defined as the three-stage model in the Recipe, an empirical equation was newly proposed as a three-fold-line model in which the short-period level was scaled with M01/3, M01/4, and M01/2 for each stage of the three-stage model. By comparing this new empirical equation against the data obtained from earthquake observation records, which included the area and stress drop of the strong motion generation area (SMGA), we found that the three-fold-line model for short-period level could match the short-period level data of SMGAs, and that the stress drop calculated from the empirical equation is independent of the seismic moment, which is consistent with the observational stress drop data of SMGAs.

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Technical Reports
  • Sangwon LEE, Takenori HIDA, Koichi KUSUNOKI, Tatsuya ITOI
    2022 Volume 22 Issue 5 Pages 5_60-5_78
    Published: 2022
    Released on J-STAGE: November 30, 2022

    Most of the current seismic structural health monitoring technology depends on the acceleration records observed by the accelerometers installed in buildings. Recently, however, the Internet of things (IoT) has evolved, and more digital image data are utilized for various purposes than before. Since the image data during and after the earthquakes include various information including various types of damage, it is expected that it enables a new way of monitoring building damage to facilitate an agile and reasonable judgment on continuous use of a building after an earthquake. The building damage to be used for the judgement include the damage of structural and non-structural elements. This paper proposes, as a first step, a practical method of identifying parameters to estimate structural damage by using the building motion during an earthquake recorded as a single moving image. From a single moving image of seismic response of building, the inter-story drift angle and velocity of each floor are estimated by calculating the optical flow representing the velocity of each floor in the image coordinate system using the image processing methods. The structural parameters such as story stiffness, natural period and damping ratio are estimated using the recursive subspace state-space system identification method (recursive 4SID) based identification algorithm. The proposed method was verified using the results of a shaking table experiment to have the same accuracy as the conventional method using the records from accelerometer and displacement meter.

    The results of this study are summarized as follows:

    1) By applying the optical flow calculation method proposed in this study, a more stable and precise inter-story drift was obtained compared with those by the conventional optical flow method.

    2) The inter-story drift angles, including the residual drift, obtained by the proposed method agreed well with the measurement results.

    3) The results of system identification by the proposed method had almost the same accuracy as the results by the accelerometer in terms of the change of the natural period and story stiffness of a building due to nonlinear building response.

    4) The proposed method successfully identifies the change of the relationships between the story shear force and the inter-story drift during earthquake excitation. The tendency of the story stiffness to decrease immediately after the inter-story drift angle increased was observed.

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