Masakatsu Miyajima

Seismic intensity estimation through questionnaire survey and collapse rates of various building types in the 2003 Bam, Iran, Earthquake

Seismic intensity in the epicentral area of the 2003 Bam, Iran earthquake is estimated using a questionnaire survey conducted two months after the earthquake. The estimated average seismic intensity on the Japan Meteorological Agency (JMA) scale is 6.1 (VIII to IX in the MMI scale). The peak frequency of the horizontal-to-vertical spectral ratio derived from microtremor measurements conducted during reconnaissance is also compared with the seismic intensity. Collapse rates for various structure types, such as adobe, unreinforced/reinforced masonry, steel-frame, and reinforced concrete, are obtained by counting the number of demolished buildings within an area of about 50-m radius around an observation point. Results show large differences in collapse rates between unreinforced and reinforced masonry, and suggest the upper limit of seismic intensity that unreinforced masonry can sustain. This fact can be utilized for an initial damage assessment within affected areas after large earthquakes.

Hospital resilience to natural hazards: classification and performance of utilities

Purpose – The purpose of this paper is to: explore major and potential challenges facing healthcare facilities operation specifically those related to utility supplies; and quantify the impact of utility supplies interruption on the operation of healthcare facilities through the development of an estimation model. Design/methodology/approach – A pluralistic qualitative and quantitative research approach benefiting from an online computer program that applies the discriminant function analysis approach. Information was collected from 66 hospitals following three major earthquakes that struck northeast Japan in 2003. Findings – Analysis demonstrated that healthcare utilities face three major challenges: vulnerability of infrastructure to natural hazards; low performance of alternative sources; and lack of consideration of healthcare utility supplies in resilience codes and legislations. The study also proposed a method to estimate the impact of utility interruption of healthcare facilities. A model has been...

Effects of topographic and geological features on building damage caused by 2015.4.25 Mw7.8 Gorkha earthquake in Nepal: a preliminary investigation report

BackgroundThe 2015.4.25 Gorkha earthquake affected about eight million people in Nepal. Most injuries and loss of life were due to building collapse and damage. This work aims to investigate the topographical and geological effects on the severe damage caused by this earthquake.FindingsIn one-week field investigation in the earthquake-affected areas, several severely damaged areas with different topographic and geological features were surveyed, as well as the site of Kaligandaki River landslide dam failure. Some general tendency related to the building damage and landslide dam failure was obtained.ConclusionsThrough the field investigation, it was found that geological and geomorphological characteristics of a site, combined with the structure feature of the building, such as the short column effect, amplified the seismic vibration and caused severe building collapse and damages, i.e., 1) For buildings on flat area consisting of lacustrine deposit or diluvial deposit, resonance effect might be the main reason, while for the buildings on the top of hills or narrow ridges, topographic effect and sometimes, short column effect should take the main responsibility; 2) For buildings located on the gentle slopes or landslides, the settlement in the infill side caused by the strong seismic vibration can be the main reason; 3) Besides of the building failure on lacustrine deposit, failure patterns in three types of topographic and geological features, i.e., narrow ridges formed by landslides, diluvial deposits and alluvial fans, and landslides, were proposed as the possible mechanism of the building damage caused by the earthquake. For landslide dam failure, it was found that landslide dam could easily breach or collapse, when the landslide-dam-deposits were fine.

A fast topographic characterization of seismic station locations in Iran through integrated use of digital elevation models and GIS

We present topographic slope positions of seismic stations within four independent networks (IGUT, IIEES, GSI, and BHRC) in Iran through integrated use of digital elevation models and GIS. Since topographic amplification factor (TAF) due to ground surface irregularity could be one of the reasons of earthquake wave amplification and unexpected damage of structures located on the top of ridges in many previous studies, the ridge stations in the study area are recognized using topographic position index (TPI) as a spatial-based scale-dependent approach that helps in classification of topographic positions. We also present the correlation between local topographic positions and Vs30 along with Voronoi tiles of two networks (IGUT and IIEES). The obtained results can be profitably used in seismology to establish homogeneous subnetworks based on Voronoi tiles with precise feedback and in the formulation of new ground motion prediction equations with respect to topographic position and topographic amplification factor.

Learning lessons from the 2011 Van Earthquake to enhance healthcare surge capacity in Turkey

ABSTRACT Historically, Turkey has adopted a reactive approach to natural hazards which resulted in significant losses. However, following the 1999 Kocaeli Earthquake, a more proactive approach has been adopted. This study aims to explore the way this new approach operates on the ground. A multinational and multidisciplinary team conducted a field investigation following the 2011 Van Earthquake to identify lessons to inform healthcare emergency planning in Turkey and elsewhere. The team interviewed selected stakeholders including, healthcare emergency responders, search and rescue services, ambulance services, and health authority representatives, in addition to conducting a focus group. Data were analysed according to an open coding process and SWOT (strength, weakness, opportunity, and threat) analysis. The findings suggest that the approach succeeded in developing a single vision by consolidating official efforts in a more structured way, mobilising many governmental and non-governmental organisations, securing significant amounts of resources including physical and human, and increasing the resilience and flexibility of infrastructure to expand its capacity. However, more attention is required to the development of stronger management procedures and acquisition of further resources.

Investigation of shallow landslides triggered by heavy rainfall during typhoon Wipha (2013), Izu Oshima Island, Japan

BackgroundTyphoon Wipha struck Izu Oshima Island on 16 October 2013, bringing heavy rainfall. It triggered widespread landslides on the western slopes of Izu Oshima Island, and caused significant loss of life and serious property damage. Authors have conducted both field investigations and laboratory experiments in an effort to understand the initiation mechanism of the shallow landslides triggered by heavy rainfall.ResultsPyroclastic-fall deposits on the slopes are well-graded fine sand with silt, and with high specific gravity and void ratio. These soil properties will affect the mechanical and hydraulic characteristics of soil. The results of consolidated-undrained triaxial tests show that the effective internal friction angle of soil is 38.7 degrees. The results of triaxial tests using pore-water pressure control show that static liquefaction can occur in porous pyroclastic-fall deposit layers due to rainfall infiltration.ConclusionsThe effective strength of pyroclastic-fall deposits on the upper slope is quite high. Even though the slope is very steep (over 30 degrees), it can remain stable while in an unsaturated condition. Due to heavy rainfall and the porosity of the pyroclastic-fall deposits, rainfall can quickly infiltrate into soil layer. Moreover, the interface above the underlying basalt will stop groundwater infiltration, acting as an impervious boundary. With increase of groundwater level, the effective strength of the porous soil will decrease. Finally, static liquefaction can be triggered, leading to the generation of shallow landslides on the upper slopes.

Liquefaction Countermeasure Technique by Using Logs

During 2011, Great East Japan Earthquake in Japan, extreme liquefaction caused extensive damage to residential houses in the Kanto Plain region and resulted settlements and tilts larger than that was observed during past earthquakes. This paper deals with a proposal of ground improvement technique by installing logs into loose sand layer as a soil liquefaction countermeasure for residential houses. Small-scale shaking table tests in a 1-g gravity field were carried out using some model grounds. It was clarified that the wooden pile could increase the resistance of ground against liquefaction due to the increase of ground density by piling and the dissipation of excess pore water pressure along the surface of piles. As a result, the magnitude of settlements of the house which was set on the improved ground by piling logs became quite small.

Study on the Applicability of Currently Used Soil-Pipe Interaction Equations for Segmented Buried Pipelines Subjected to Fault Movement

This study investigates the applicability of force-displacement equations suggested in currently used design codes, based on “Guidelines for the seismic design of oil and gas pipeline systems” of ASCE (1984)[1] as their main reference, to introduce the soil-pipe interaction for segmented type of pipeline systems. Hence, results of finite element method (FEM) analyses are verified by full-scale experiments on a segmented ductile iron pipeline with 93mm diameter and 15m length. Pipeline is installed at a 60cm depth from the ground surface in two types of sandy soil with different values of sub-grade reaction. Adopted fault is a reverse type which has an intersection angle of 60 degrees with pipeline and moves in three same steps to reach its total movement of 35cm. Findings reveal that the aforesaid interaction equations are basically developed for continuous pipelines and the effect of connection joints on the integrated structural behavior of segmented pipelines is not considered in them. Hence, suggesting them by currently used guidelines for seismic design of fault crossing segmented pipelines leads to overestimation of soil resistance against relative downward movement of pipeline in surrounding soil continuum.

Relation between building damage and ground conditions in the 1999 quindio earthquake in Colombia

An earthquake of magnitude 6.2 (M b ) occurred in west-central part of Colombia on January 25, 1999. This earthquake is officially called Quindio Earthquake from the name of the most affected province. The earthquake caused disastrous damage to a large number of buildings resulting in significant casualties. In Armenia City and its neighbouring villages close to the epicentre over 1000 people were killed by the earthquake and the total monetary loss reached US

Topographic characterization of seismic networks using topographic position index and Voronoi tiles: a case of the Hokuriku region, Japan

2 billion. Armenia City, which has an approximate population of 280 000 people, apparently suffered the worst in terms of casualties and damage to the buildings. The present paper focuses on the causes of damage to houses and buildings in Armenia City. First, the evolution of the urban area of the city was investigated using historical features available maps from each era. Then a correlation between buildings damage and topographical features of the city was studied. The effects of geological features and amplification of ground motion were also investigated.