Journal of Earthquake and Tsunami

Some seismic design codes require to determine earthquake motions at ground surface, although we need sometimes a motion at engineering basement of ground. For example, it is necessary for optimal design of structures to introduce effects of soil-structure interaction and to input ground motions to engineering basement, which should satisfy the motions at surface required by a design code. This is simplified as a problem to find a possible input signal of a known non-linear-single-input and single-output (SISO) system with a given output signal. This study proposes a very simple algorithm to find a possible input signal for a known SISO system satisfying a given output signal from the system. The proposed algorithm searches for a possible input signal, whose system response is similar in shape to the given output signal, without any system identifications. Thus, it is not an inversion technique; it is an algorithm used to search for one of the possible input signals. Herein, the proposed algorithm is described and its performance is demonstrated using numerical examples.

Earthquake source parameters such as slip distribution and slip rate are useful information for understanding the physical processes behind earthquakes. The isochrone back-projection method, or isochrone-BPM, is one of the methods used to obtain slip distribution in the fault plane by incorporating the isochrone concept with back-projection method. Isochrone-BPM has advantages in its ease of implementation. However, it appears that the resulted slip distribution images always contain artifacts causing the images to be smeared. The emergence of these artifacts may lead to misinterpretation of the slip distribution, thus becoming a major weakness of isochrone-BPM. In this work, an alternative approach is proposed by utilizing least-square inversion scheme with the addition of damping factor as an alternative to the isochrone-BPM, which is then referred to as damped isochrone inversion since it still utilizes the core formulation of isochrone-BPM. The application of isochrone-BPM slip inversion to synthetic data generated from a test model shows that the quality of the resulted image will highly depend on the set of receiving stations used. In addition, the isochrone-BPM image will also depend on the focal mechanism of the earthquake, which is indicated by the difference in patterns on different mechanisms. Contrary to isochrone-BPM, the damped isochrone inversion produces slip distribution images that do not depend on the set of receiving stations used and do exhibit dependence on the focal mechanism. These results may suggest that as an alternative to the isochrone-BPM, the damped isochrone inversion offers better performance in recovering the slip distribution images.

This study discusses the composition and distribution of paleo-liquefaction structures, their triggering mechanisms, probable source and the dynamics of source faults expressed in the Kashmir basin (KB), NW Himalaya. Stratigraphic evidences of deformational structures along concomitant fault zones are highly preserved throughout the basin. The KB was frequently confronted with recurrent seismic activities along intra basinal active faults and adjacent active faults during differential uplift of Himalaya, which resulted in various deformation structures during and after the evolution of the KB. Past earthquake events released a significant part of the slip deficit along intra basinal active faults and vertically offset quaternary deposits by 1–3m and originated different and extensively deformation structures. In this context, stratigraphic sections and paleo-surface ruptures have been meticulously mapped to determine the seismic nature and the source of resultant causative earthquakes. The results of this study suggest that besides southern thrust systems, intrabasinal active faults are the main probable seismogenic sources responsible for development of these structures and play an important role in releasing the accumulated stresses in this region.

Aftershock records have a considerable effect on the results of collapse assessments conducted on buildings. Thus, they should be selected cautiously. As the number of recorded aftershocks is not sufficient, mainshock records are often utilized instead. In order to increase the correlation between the aftershock time history and the seismic response of a structure, this research intends to investigate several Intensity Measures (IMs). For this study, three RC frames were considered. Forty-four far-field records from FEMAP-695 were selected as main and aftershock. Each building analysis was conducted under 44 mainshock–aftershock chains. According to the results, use of the summation of the first mode spectral acceleration value of aftershocks as the second part of a vector IM can lead to the sufficiency of the IM.

In this study, friction dampers (FDs) were placed at the top and bottom of a post-tensioned (PT) self-centering glulam (SCG) beam-to-column joint to dissipate earthquake energy. PT tendons were installed in two externally elongated slots at the centroid of the beam to provide the system with self-centering capacity so that the system can return to its original position after an earthquake. Theoretical and experimental analyses of the beam-to-column joint were performed to investigate the effects of various design parameters, such as the total clamping forces applied to the FDs and initial forces of the PT tendons, on the hysteretic performance of the FD-SCG joint under cyclic loading. During the tests, the backbone members (glulam beam and column) and main connecting members (PT tendons and FDs) were measured to always be within the elastic limit range. Both the theoretical and experimental results indicated that under low initial PT forces and clamping forces, the energy is dissipated primarily by FDs; in contrast, under high PT forces and clamping forces, some energy is dissipated by the glulam materials, owing to the occurrence of minor local damage in the specimen, in the direction perpendicular to the grain. Moreover, the FD-SCG joint can be suitably designed to achieve the desired stiffness, load capacity, self-centering ability, energy dissipation capability, and expected overall system response.