Nakamura Method Research Articles

Revelations from a single strong-motion record retrieved during the 27 June 1998 Adana (Turkey) earthquake

During the 27 June 1998 Adana (Turkey) earthquake, only one strong-motion record was retrieved in the region where the most damage occurred. This single record from the station in Ceyhan, approximately 15 km from the epicenter of that earthquake, exhibits characteristics that are related to the dominant frequencies of the ground and structures. The purpose of this paper is to explain the causes of the damage as inferred from both field observations and the characteristics of a single strong-motion record retrieved from the immediate epicentral area. In the town of Ceyhan there was considerable but selective damage to a significant number of mid-rise (7–12 stories high) buildings. The strong-motion record exhibits dominant frequencies that are typically similar for the mid-rise building structures. This is further supported by spectral ratios derived using Nakamura's method [QR of RTRI, 30 (1989) 25] that facilitates computation of a spectral ratio from a single tri-axial record as the ratio of amplitude spectrum of horizontal component to that of the vertical component [ R= H( f)/ V( f)]. The correlation between the damage and the characteristics exhibited from the single strong-motion record is remarkable. Although deficient construction practices played a significant role in the extent of damage to the mid-rise buildings, it is clear that site resonance also contributed to the detrimental fate of most of the mid-rise buildings. Therefore, even a single record can be useful to explain the effect of site resonance on building response and performance. Such information can be very useful for developing zonation criteria in similar alluvial valleys.

The reference spectral noise ratio method to evaluate the seismic response of a site

The seismic response of several sites in the Durban area of South Africa has been investigated using a refined version of the spectral ratio (H/V) generated by cultural seismic noise. Two samples of noise separated by an interval of several minutes for the vertical and the two orthogonal horizontal components were taken at each site. Though the two samples differed noticeably in the time as well as in the frequency domain, when the components are considered separately, the ratios of the horizontal to the vertical spectra were very similar for most of the pairs. This similitude was obvious not only in the frequencies of the peaks, but also in the range of amplifications involved. These observations have been used to introduce a refinement to the Nakamura Method. This refinement consists in using as a reference the H/V spectral ratio of a well-known, hard rock site. All the other soft sites of interest are then compared with this standard reference site. This comparison provides valuable information on the frequencies and amplification factors introduced by the critical soft sediments. This refined method will be referred here as the ‘Reference spectral noise ratio’.This method, is compared to a similar one devised to investigate the response of horizontal layers to longitudinal seismic waves, using the ratio of the spectra generated by long- period waves.

Seismic microzonation in Australia

Since the 1980s seismic microzonation studies have been undertaken in Australia to assess the likely effects of earthquakes on urban centres built on unconsolidated sediments. Presently the Nakamura method is used for processing data. So far parts of Perth, Adelaide, Cairns, Gladstone, Rockhampton, Newcastle, Sydney and Launceston have been zoned. The Launceston, Tasmania, study was the pilot study for many of these as it refined the methodology used and the data obtained were incorporated into a GIS database. Building heights and site factor zoning maps were produced for the Launceston City Council. One of the major activities, of the new initiative by the Australian Geological Survey Organisation (AGSO), popularly known as the ‘Cities Project’, is coordinating seismic microzonation throughout Australia. Microzonation data have been included in AGSO’s geohazards GIS database. This is helping local councils zone land for seismic hazards. State Emergency Services use the information to plan for emergencies resulting from the effects of earthquakes. These practical applications of seismic microzonation data will help mitigate the destructive effects of any future large earthquakes occurring near major urban centres. In the Launceston case it was found that there is a variable risk dependant on epicentral distance and the nature of relatively unconsolidated sediments in various parts of the city. Disastrous amplification could occur at some sites.

On the use of microtremor recordings in seismic microzonation

Experimental methods involving microtremor recordings are useful for determining site effects in regions of moderate seismic activity where ground motion records are few, and in urban or industrial contexts where the noise level is high. The aim of this study is to establish a microzonation by using the Nogoshi–Nakamura method, [1, 2]a simple experimental technique based on microtremor recordings. Since the physical phenomena underlying the method are only partially understood, the spectral responses obtained cannot be used alone. We, therefore, complete our experimental results by comparing them with the solutions of a one-dimensional numerical simulation (SHAKE91). [3, 4]The experimental programme was carried out on a plain near the Rhone Delta (South of France). H/ V spectral ratios were calculated at 137 noise measurement points. In addition, we were able to compute the numerical transfer functions from soil columns defined by geotechnical characteristics inside the studied region. A comparison of the results obtained by the experimental and numerical methods showed that the fundamental frequencies are in good agreement, but that the amplitudes obtained by the two techniques are sometimes different. The analysis of H/ V spectral ratios enabled us to establish maps to characterize the region: a resonance frequency map and maps of amplification levels as a function of frequency range, leading to a seismic microzonation for the whole of the region.

HORIZONTAL‐TO‐VERTICAL SPECTRUM RATIO OF EARTHQUAKE GROUND MOTION FOR SITE CHARACTERIZATION

Nakamura's method, which uses a horizontal-to-vertical Fourier spectrum ratio of microtremor, has become popular to determine the predominant period and amplification of a site. In this study, this method is extended for earthquake ground motion recordings using new strong motion data recorded by JMA-87-type accelerometers. From the analysis of these accelerograms, horizontal-to-vertical Fourier spectrum ratios of a site for different earthquakes are also found to be stable irrespective of magnitude, distance and depth. To establish this fact, attenuation relations of velocity response spectra for horizontal and vertical components are derived for three damping ratios (0, 2 and 5 per cent) using the JMA data. Then the horizontal-to-vertical ratios of the velocity response spectra are obtained. The results show that the horizontal and vertical velocity response spectra are dependent on magnitude, distance and depth, but that their ratios are almost independent of magnitude, distance and depth. However, since the current data set consists of mostly intermediate to far field data, this observation should be limited to records of these distance ranges. Introducing station coefficients, representing site amplification, to this relation yields the value comparable to the horizontal-to-vertical Fourier spectrum ratio at a specific site. The stability of the spectrum ratio is explained by the transfer function between the ground surface and stiff-soil outcrop due to S-wave propagation. These results suggest that site amplification characteristics can be evaluated by one-point two-component surface recordings of earthquake ground motion, in a similar manner as proposed by Nakamura for microtremor. © 1997 by John Wiley & Sons, Ltd.

Site amplification at five locations in San Francisco, California: A comparison ofSwaves, codas, and microtremors

AbstractWe compare microtremor data to weak-motion S-wave and coda recordings at sites in San Francisco in order to clarify the range of applicability of microtremor data to ground-motion prediction. We also compare S-wave results to coda results. For each type of data, we compute spectral ratios of motions from two soil/rock station pairs and from an uphole/downhole pair in the Marina district. We compute horizontal/vertical ratios (Nakamura's method) at a soil site, a rock site, and the surface and borehole instruments. In the station-pair analyses, microtremor data show amplifications at the same fundamental frequency as S waves, but the frequencies of other peaks do not agree. The amplification at frequencies higher than 2 Hz is greater in the microtremor data. Station-pair ratios of coda data generally show spectral peaks occurring at the same frequencies, but with levels varying from one to four times the amplification from S-wave ratios. Nakamura's method of analyzing microtremors agrees better with S-wave station-pair results than the microtremor station-pair method over a limited frequency band that varies from station to station.

Unsteady free convection flow over a continuous moving vertical surface

The problem of heat transfer in the unsteady free convection flow over a continuous moving vertical sheet in an ambient fluid has been investigated. Both constant surface temperature and constant surface heat flux conditions have been considered. The nonlinear coupled partial differential equations governing the flow have been solved numerically using the Keller box method and the Nakamura method which both give closely similar solutions. The results indicate that the cooling rate of the sheet can be enhanced by increasing the buoancy parameter or the velocity of the sheet. It is found that a better cooling performance could be achieved by using a liquid as a cooling medium rather than a gas. The overshoot in the velocity occurs near the surface when the buoyancy parameter exceeds a certain critical value.

Earthquake site-response study in Giumri (formerly Leninakan), Armenia, using ambient noise observations

We have tested whether ambient noise observations reveal useful information regarding site response at sediment sites in Giumri (formerly Leninakan), Armenia. This was done by comparing the noise observations with spectral-ratio site-response estimates based on aftershock data of the 7 December 1988 earthquake. We show that neither the horizontal-component noise spectra alone, nor spectral ratios taken with respect to a nearby bedrock site, reveal useful information regarding site response. However, spectral ratios of horizontal components taken with respect to vertical components (Nakamura's method) exhibit a prominent peak that corresponds to the fundamental resonant frequency observed in the aftershock data. Based on this and other recent investigations, we conclude that Nakamura's method may be a reliable procedure for determining the fundamental resonant frequency of sedimentary deposits from ambient noise observations.

Numerical and Theoretical Investigations on the Possibilities and Limitations of Nakamura's Technique.

Numerical simulation of noise is used to investigate the characteristics of the spectral ratio between horizontal and vertical components (H/V ratio) and its sensitivity to various parameters in order to better appreciate the reliability of the technique proposed by Nakamura (1989) to estimate site amplification effects from single station noise recordings. Noise is simulated as the signal produced at a single site by a set of superficial sources (unidirectional forces or dipoles) disposed all around with random amplitude and time delay. Individual signals from a single source are computed by the discrete wave number technique. Synthetic calculations for 15 soil profiles show that this ratio exhibits a single, clear peak, the location of which is independent of the source excitation function, but strongly correlated with the local geological structure: its frequency is very close to the S wave resonance frequency. This peak appears to be mainly controlled by the polarization curve of the fundamental Rayleigh waves, which in turn exhibits a sharp peak around the fundamental resonance mode of the sedimentary structure. A similar result is found for the H/V ratio obtained for incident plane SV waves. In contrast, the amplitude of this peak exhibits a poor correlation with the ground motion amplification of S waves at resonance frequency. It is shown to be related with a high sensitivity on the value of the Poisson's ratio in the uppermost layer presumed to be the noise source layer, and, though to a much lesser extent, on the mean distance between site and noise sources. It is concluded that Nakamura's method can clearly allow the resonance frequency of a given sedimentary site to be measured very efficiently and very cheaply, but that its use for deriving the amplification at resonance frequency seems still premature from a theoretical point of view.

Estimation of obliquely oriented free anisolropy angle and particle field distribution dispersion parameter

I. Taganwa Y. Nakamura's method to measure a perameter ΔHc/Hc of anisotopy field distribution has been shown to be useful for its demagnetization correction free. In order to estimate the easy axis of obliquely oriented tapes, the angular dependence of the ΔHc/Hc in out-of-plane measurements was made for Hi-8 VCR ME (Metal-Evaporated) tape and obliquely oriented trial metal particle tapes. The easy axis direction in out-of-plane is estimated from the angular dependence of ΔHc/Hc without troublesome demagnetization correction. Particle disperaion and orientation ability of the magnetic paint is tried to estimate from the SQR ΔHc/Hc relations.

頚髄症における手指機能検査（中村法）の検討

Nakamura Method is an evaluating system of motor function for patients with cervical myelopathy. It consists of five items. The authors examined reliability of the Nakamura Method in 34 patients with cervical myelopathy. The authors conclude that the Nakamura Method is a valuable evaluating system.

A solution algorithm for fuzzy linear programming with piecewise linear membership functions

This paper deals with the fuzzy linear program with continuous piecewise linear membership functions. A fuzzy linear program with piecewise linear membership functions has been considered by Hannan and Nakamura. Hannan's method can solve the problems only when all membership functions are concave in the range (0, 1) and Nakamura's method needs to use the linear programming technique repetitionally. We propose a technique to solve the problem using a standard linear programming when membership functions are strictly quasiconcave and the minimum operator is adopted for aggregating fuzzy goals. The repetitional use of linear programming technique is not required in our method.

Dielectric relaxation in OH—O bond complexes

Abstract The dielectric absorption of the mixtures of Phenol with Acetone and Ethyl methyl ketone having different concentration ratios (3:1, 2:1, 1:1, 1:2 and 1:3) has been determined at microwave frequency 9.8 GHz, at 33°C. The dielectric data have been analyzed, to yield relaxation times and dipole moments, using Higasi method and Higasi, Koga and Nakamura method. All the mixtures yielded high values of the distribution parameter indicating the flexible nature of the OH-O type hydrogen bonding. The high values of the relaxation times and dipole moments give confirmative results for the association of the phenol with these electron donar molecules in all mixtures investigated.

Relaxation behaviour of phenol and cresols in highly viscous media

Dielectric relaxation times (t) have been determined for phenol,o-cresol,m-cresol andp-cresol in solutions ofn-heptane+paraffin oil of varying viscosities. Since, all the four systems contain an -OH group, capable of group rotation, the dielectric absorption was further resolved using Higasi, Koga and Nakamura method in terms oft(1) andt(2). In each case the dielectric relaxation time has been found to be maximum in the neighbourhood of 75%n-heptane+25% p.o. in the mixture. On further increasing the viscosity of the medium, theT values shorten. The results obtained suggest the associative nature of the compounds investigated.

Dielectric Relaxation Processes in Some Substituted Amides in Dilute Solutions

Abstract The dielectric measurements have been carried out in the microwave region (3.1 cm) over a range of temperatures on propionamide, N-methylpropionamide, N,N-dimethylpropionamide, and N-ethylacetamide. All the molecules except propionamide exhibit high value of distribution parameter. The dielectric dispersion, when resolved by Higasi, Koga, and Nakamura method gives two relaxation times τ(1) and τ(2) widely different from each other, suggesting the two separate processes occurring in the system. The enthalpies for different processes involved have been evaluated by the Eyring equations. The comparison with NMR data of enthalpy to ΔHτ(1), which is related to the process other than molecular, suggests that the rotation of–NR2 group around the carbonyl carbon nitrogen bond is not feasible. The observed result indicates that this may be due to group inversion process. These results are in agreement with the earlier investigations of Saxena et al. on some substituted amides and of Phillips on N,N-dimethylamide using proton resonance spectra. The substituted amides in dilute solution of benzene exhibit some association with the benzene molecules.

Macroscopic Viscosity and Dielectric Relaxation Process of Ethyl and Butyl Acetates

Abstract Dielectric constants and losses have been measured at 9.8 GHz microwave frequency for ethyl and butyl acetates in benzene and benzene–paraffin oil mixtures at 18 °C. The data obtained has been analysed in terms of the two relaxation times τ(1) and τ2 using Higasi, Koga, and Nakamura method and their dependence on the viscosity has been examined. Since the observed values of τ(1)and τ(2) are significantly different, the systems studied represent two Debye type dispersions. It has been found that the relaxation behaviour giving rise to τ(1) in both the ester molecules is not effected to any appreciable extent by the increased macroscopic viscosity. The dielectric relaxation time τ(2) associated with the molecular process lengthens with the increasing macroscopic viscosity of the medium.

THE TIME USE SURVEY IN STROKE IN-PATIENTS

The time use of in-patients in daily life activities was analysed. The activities of 125 patients were objectively recorded every 10 minutes, and classified into 8 groups following Nakamura's method (1975).The stroke in-patients spent less time for social activities such as conversation, games, watching television, reading, etc., and more for sleep, self-care activities, resting or idleness, and medical care than normal subjects of which data were obtained from the report of NHK Public Opinion Research Institute (1974). It was assumed that to be a disabled and to live in a hospital rendered a man premature aging in the way of life.The correlation between time use, and individual factors of the patients such as motor age (Johnson-Zuck, et al.), the age, and WAIS score showed that these factors influenced differently the time usage of the patients. Also the time schedule for medical treatment was related to the time use. Thus, the time usage of the stroke in-patients linked complicatedly with the individual and environmental factors.The application of time use survey for the analysis of deviation in daily life activities was proposed and discussed.

特性関係ゲームのコアの存在に関して

Nakamura establishes a theorem which gives necessary conditions for a simple game with ordinal prefer- ences to have a nonempty core. The conditions are also sufficient, if the set of alternative outcomes is finite. In the present paper, we will show that Nakamura's method of the proof of this theorem makes it possible to generalize the theorem to an arbitrary characteristic function game with ordinal preferences.

日本一の長寿者泉重千代翁(114才)と良導絡治療

The author had the opportunity to give Ryodoraku treatment to the Japanese longestlived person, Mr. Shigechiyo Izumi, 114 years old, was born in 1865. He lives in a small island in Kagoshima prefecture, called Tokuno-shima. Through a whole year, this island has warm temperature and has neither snowing, frosting nor polution.He has hardly had a day's illness, but he is recently complaining abdominal distention and constipation. By the General Ryodoraku measurement, the excitation of H2, H3 and the inhibition of H4, H5, F4 are slightly recognized. So the author gave Ryodoraku regulation on these points. Ryodoraku treatment on REPP (Reactive Electro Permeable Point) in the region of lower limbs and abdomen has brought excellent results. The values of General Ryodoraku measurement almost settled between 10 and 30, which was admirable result. Besides, the result of blood test and clinic pathological tests of the heart, the kidney and the liver showed good conditions.By the way, Mr. Shigechiyo Izumi has been taking the Dr. Nakamura's method of brush needle treatment since two years ago.

THE EFFECT OF THE RETURN TO OKINAWA FOR SUMMER VACATION ON HEAT TOLERANCE, COLD TOLERANCE AND PERIPHERAL COLD TOLERANCE OF THE SUBTROPICAL MIGRANTS TO THE TEMPERATE ZONE

Sweating test and peripheral cold tolerance test were performed on 10 young male university students born and raised in Okinawa (the subtropical zone) but moved to the Japanese Main Islands (the temperate zone) within last three years and cold tolerance test was made on five subjects. Two series of experiments were performed in Nishinomiya, using a climatic chamber. The first series of experiments was performed in July before the return of the subjects to Okinawa (the experiment 2). The second series of experiments was performed in September after a month's stay in Okinawa in August (the experiment 1). Sweating reaction was examined on the subjects dressed in shorts only 60 min by immersing both legs in stirring water of 42 C in a room of 30 C with 70% R.H. Cold tolerance test was performed on the subjects clothed with 1.8 clo by taking off a blanket after covering with a blanket in supine position for 20 min in a room of 10 C with 70% R.H. Physiological responses of the subjects to cold were observed for 60 min. Peripheral cold tolerance test was made by dipping the left middle finger with a thermocouple attached to the nail bed into ice water for 30 min and changes of the skin temperature were measured continuously. Greater sweat volume, lower sodium concentration in sweat at the given sweat rate and less rise in oral temperature in the experiment 1 than in the experiment 2 were observed.These results indicate acclimatization to heat of the subjects was induced by the return to Okinawa in summer and heat tolerance of the subjects was slightly improved when assessed by numetrical heat tolerance index after a month's stay in Okinawa in summer.In cold tolerance test, significantly greater increase in the metabolic rate, greater frequency of shivering and considerably lower drop of the mean skin temperature in the experiment 1 than in the experiment 2 were observed. These results indicate the ratio of increase in the metabolic rate to thedrop in the mean skin temperature during cold exposure was greater in the experiment 1 than in the experiment 2. Thus it might be said that cold tolerance was reduced by the return to Okinawa in summer and living in a hot and humid climate. The mean value of time for first temperature rise of the vascular reaction of finger in the cold was significantly greater in the experiment 1 than in the experiment 2. The mean value of resistance index of frost bite caluculated by the Nakamura's method was significantly smaller in the experiment 1 than in the experiment 2. It may thus be concluded that the vascular reaction of finger in the cold is depressed and peripheral cold tolerance is reduced after the returnto Okinawa in summer.