1 Earthquake Engineer Group, OYO Corporation, Tsukuba, Japan 2 Department of Built Environment ,Tokyo Institute of Technology,Yokohama, Japan 2 Professor, Department of Built Environment ,Tokyo Institute of Technology,Yokohama, Japan Email: ryu-ei@oyonet.oyo.co.jp, kmoto@enveng.titech.ac.jp,seo@enveng.titech.ac.jp ABSTRACT : Taipei basin suffered serious damage on building structures during the 1999 Chi-Chi earthquake, even though it was located 100 km away from the epicenter. The purpose of this paper is to discuss the relationship between the damage occurred and the ground motion characteristics observed in the Taipei basin and to draw a seismic microzoning map for the region by taking into account the analyzed results about the earthquake motions, microtremors and the damage distribution. For more discussion about site effect evaluation, observed strong motions of two earthquakes, which happened in 1994, 1995 will be used in addition to the 1999 earthquake. Such records of strong motions of those earthquakes were offered by the Central Weather Bureau (CWB), Taiwan. Measurements of microtremors inside Taipei basin were made in 2000 after the Chi-Chi earthquake.

2007年能登半島地震では，能登半島北部地域を中心に大きな被害が発生した。とくに，震源域の輪島市門前町中心部の走出や道下地域で木造家屋の倒壊が数多くみられた。この地域は，南北を山地に挟まれた八ケ川沿いに広がっており，地盤条件は良好ではない。Yamanaka et al.（2008）は，この地域で余震観測を実施し，被害の多かった地点では表層地盤による地震波の増幅を示唆する明瞭な卓越周期が存在することを明らかにした。こうした地盤増幅特性を理解するために，この余震観測が行われた７地点において半径1mから1kmまでの複数のアレイで微動の上下成分の観測を実施し，周期0.1秒から３秒の間でレイリー波の位相速度を求めた。各地点での位相速度の逆解析により，深部および表層地盤の１次元Ｓ波速度構造を明らかにした。これらの地盤モデルを用いて，門前町地域でのＳ波の地盤増幅特性について検討した。表層地盤に対するＳ波の１次元理論増幅特性の卓越周期は，余震観測による地盤増幅特性の卓越周期とほぼ一致しており，地盤モデルが妥当なものであることがわかった。また，観測増幅特性のピーク振幅は，得られた地盤モデルの深さ30ｍまでの平均Ｓ波速度と線形関係にあることがわかった。しかし，ピーク振幅の絶対値は，１次元地盤モデルでは説明できず，表層地盤の２・３次元構造の影響の可能性が示唆された。

In this paper, we discuss the propagation process of ground motions generated by two earthquakes through the analysis of seismograms recorded on rock and sediment sites. Significant later phases following the S-wave arrivals in horizontal components often appear in the ground motions recorded in the sedimentary plain. We applied 2-D finite difference method to simulate the later phases during the earthquakes observed at the sediment sites using the subsurface structures derived from the seismic and microtremors prospecting process. The results indicate that when considering basin-excited waves, the characteristics of the simulated waveforms including the later phases display good agreement with the observed seismograms. Moreover, the earthquake motion characteristics were clarified by the propagation process of seismic waves in the western part of Nobi Plain. We also clarified effects of the irregular underground structure on the Basin-Induced Love waves propagation.

1 Research Fellow, Dept. of Construction System Engineering, Aichi Institute of Technology, Toyota, Japan 2 Research Associate, Dept. of Built Environment, Tokyo Institute of Technology, Yokohama, Japan 3 Professor, Dept. of Built Environment, Tokyo Institute of Technology, Yokohama, Japan 4 Professor, Department of Civil Engineering, Aichi Institute of Technology, Toyota, Japan Email: k-sagu@aitech.ac.jp

Heavy damage occurred in Monzenmachi, the Wajima city, in the northern part of the Noto peninsula during the 2007 Noto Hanto earthquake with an Mj of 6.9. The area is located along a river and sandwiched by mountains at the northern and southern ends of a Quaternary narrow valley 1–2 km wide. The seismic intensity observed in the area was 6 upper during the main shock. In this study, we conducted observations of ground motions during aftershocks in Monzenmachi to understand local site effects in the vicinity of the seismic intensity station. We installed 11 accelerometers in three areas of Monzenmachi, Hashiride, Touge, and Kuroshima. In each area, three or five stations were chosen for a deployment of a linear array across the areas with heavy damage. The analysis was performed using aftershock records observed during events with Mj of 2.3–4.4. The spectral ratio of records from the station near the seismic intensity station to a reference station on Tertiary layers shows a dominant peak at a period of 1 s. We also found distinct peaks at periods of 0.4–0.7 s in the spectral ratios at the sites in the areas with heavy damage. In contrast, no dominant peaks were identified at the stations at the foot of the mountains. This clearly indicates that site amplification effects play an important role in defining the damage distribution in an area. Similar peaks were found in the H/V spectra of microtremors at the aftershock observation sites, though the peak amplitudes of the microtremor H/Vs are smaller than those of the S-wave spectral ratios.

This study aims to set up a simulation model of rescue activity for the weak in disaster during post-earthquake, and to clarify basic knowledge of efficient rescue activity with case studies of application of local disaster mitigation. Firstly, detailed fire risk of research area is shown. Secondly, questionnaire survey is carried out toward voluntary welfare worker, local disaster management organization, and citizen. Thirdly Multi-Agent model is organized by using the results of questionnaire. Case studies showed that it is necessary not only to increase the number of rescue members, but also to give them information of the weak people, to decide assignation of rescue and to consider the fire risk, in order to improve the rescue activity. It is also shown that voluntary activity of citizen is as successful as other cases.

Significant later phases following the S-wave arrivals in horizontal components often appear in the ground motions recorded in the sedimentary plain. In this paper, we discuss the propagation process of ground motions generated by a shallow earthquake through the analysis of seismograms recorded on rock and sediment sites. To accomplish it, we first deployed a temporary stations for seismic refraction prospecting to clear up the boundary between the mountain range and the edge of the sedimentary plain in the southwestern edge of the Kanto Plain. Accordingly, we employed the recordings of seismic waves generated by explosions to model the subsurface structures applying travel time analysis. We also applied 2D finite difference method to simulate the later phases during an earthquake observed at the sediment sites using the subsurface structures derived from the seismic prospecting process. The results indicate that when considering basin-excited waves, the characteristics of the simulated waveforms including the later phases display good agreement with the observed seismograms.

We conducted aftershock observations in Chuo Ward, Fukuoka city to make clear reasons why building damage had been concentrated near Kego Fault during the 2005 West off Fukuoka Prefecture earthquake. We found significantly large site amplification in the area limited within a distance of about 200 meters from Kego Fault to the northeast direction. Amplification factors in this area are evaluated to be about 3 times in PGA and PGV, and it corresponds to the increment of about 1 in seismic intensity. It can be interpreted that the amplification is affected by irregular shallow subsurface structure like basin edge effect.

This is a report on newly found photographs of buildings damaged during the 1923 Kanto Earthquake, which were originally owned by Dr. Hirohiko Yoshida (1899-1986). The total number of photographs is 942. The photographs mainly show the damage of buildings and civil engineering structures located in Tokyo and Kanagawa. Many of the precise locations could be identified from the description written in the back of the photographs and in the cardboard on which the photographs were mounted. 86 photographs were found identical to those in the official report.

Research Article| July 01, 2003 Earthquake Disasters of 13 January and 13 February 2001, El Salvador Walter Salazar; Walter Salazar Search for other works by this author on: GSW Google Scholar Kazuoh Seo Kazuoh Seo Tokyo Institute of Technology Interdisciplinary Graduate School of Science and Engineering Department of Built Environment 4259 Nagatsuta, Midori-ku Yokohama 226-8502 Japan seo@enveng.titech.ac.jp (K.S.) Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2003) 74 (4): 420–439. https://doi.org/10.1785/gssrl.74.4.420 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Walter Salazar, Kazuoh Seo; Earthquake Disasters of 13 January and 13 February 2001, El Salvador. Seismological Research Letters 2003;; 74 (4): 420–439. doi: https://doi.org/10.1785/gssrl.74.4.420 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search El Salvador is a small country in Central America (Figure 1). It has a savanna climate, with daytime temperatures consistently between 25°–30°C. The rainy season extends from May to October, while November to April is generally very dry. Rainfall is about 1,800 mm per year. These weather conditions are favorable for producing sugar and coffee. The population is about 6.0 million with a high concentration in the capital city, San Salvador, where 1.8 million persons are living now. The earthquakes of 13 January and 13 February 2001 demonstrated the high vulnerability in El Salvador and strongly affected people... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

To understand the characteristics of seismic ground motions during the 1995 Hyogo-ken Nanbu earthquake in Higashinada area Kobe city, the effects of the underground structure at the edge of the sedimentary basin on seismic ground motion were investigated using observed moderate and weak earthquake motions. A later phase can be clearly identified after S-wave onset in southern part of this area, which was generated by 2D multiple reflection wave due to the effects of the underground structure. The result of simulations suggest that the distribution of synthetic maximum amplitude ratio referred to rock site depends on input motions. Due to the basin edge effects, the distribution of the maximum amplitude ratio shows a peak at the edge of the sedimentary basin using the sine wave with period of 1s and duration of 0.5s as an input wave. Besides, the ground motion of the 1995 Hyogo-ken Nanbu earthquake observed at Kobe Univ. was used as an input motion, which shows two peaks. One peak was located near the edge of the sedimentary basin and it was generated by the basin edge effects. The other one was generated by the interference between diffracted wave and 2D multiple reflection wave and it was located at the south border area with intensity VII determined by Japan Meteorological Agency. Our results indicate that the effects of 2D multiple reflection wave generated at the edge of sedimentary basin is important for the big earthquake motions.

For the prediction of long period ground motions in Osaka basin, we investigated the propagation and generation process of them in Osaka basin using the 1995 Hyogo-ken nanbu earthquake. The seismogram observed at costal area (RKI) can be identified the long period later phase after 100sec of S-wave onset. From particle orbits and comparison of seismograms observed at other stations, there are some possibility that the propagation and generation process of the long period later phase is as following; (1): it was Love wave generated at the seismic source, and propagated to RKI via Mt. Izumi where is located at opposite side of RKI in Osaka basin. (2): it was Love wave generated at the bottom of mountain near RKI and propagated to opposite side, it was reflected at Mt. Izumi, and returned to RKI. (3): it was Love wave generated at the bottom of Mt. Izumi, and propagated to RKI.

The 1995 Kobe earthquake brought serious problems from the earthquake disaster mitigation @point of view. In this paper, several important subjects will be discussed after reviewing what happened during and after the earthquake. Most of all, the following subjects will be discussed in this paper. 1) Source model of the earthquake could be understood in detail using observed strong motions and damage direction of distributed structures. There is a possibility that one of asperities near Kobe city contributed to have brought heavy damage in Kobe city. 2) Significant later phase could be seen in the seismic record obtained in the coastal region of Kobe city. It can be explained as a surface wave that could be reflected at the southern boundary of Osaka basin. This later phase with long period component has the possibility to trigger the failure of Hanshin highway. 3) Two residential buildings, one was constructed with the older Japanese seismic code and the other one was constructed with the new seismic code that had been issued in 1981, showed different behavior during the earthquake. The former one suffered serious damage and the latter one did not suffer damage so much. After all, such experiences should be taken into account in the future strategy about earthquake disaster mitigation.