What Is the Nakamura Method?

Nakamura, Yutaka

doi:10.1785/0220180376

Cited by 91 publications

(84 citation statements)

References 7 publications

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“…Seismic properties of the subsurface can be estimated, amongst others, by the use of the ambient noise field (microtremors). Many experiments established that the H/V spectral ratio (the ratio between the amplitude spectra of the horizontal and vertical components of a seismic recording) shows a correlation with the fundamental resonance frequency of the recording site (Arai and Tokimatsu, 2005;Bonnefoy-Claudet et al, 2006a;Fäh et al, 2001; Lermo and Chavez-Garcia, 1993;Nakamura, 1989Nakamura, , 2019Scherbaum et al, 2003;Parolai et al, 2002). More recently, teleseismic phases have also been used to study the resonance of deep sedimentary basins (Nishitsuji et al, 2014;Ruigrok et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…In Groningen, the ambient noise field contains a frequency-and time-dependent mixture of body and surface waves. This makes it doubtful whether the estimated H/V ratios need to be interpreted in terms of surface-wave ellipticities (Malischewsky and Scherbaum, 2004), body-wave resonances (Nakamura, 1989(Nakamura, , 2019 or a mixture of wave types (Sánchez-Sesma et al, 2011;Lunedei and Malischewsky, 2015;Spica et al, 2018a).…”

Section: Introductionmentioning

confidence: 99%

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Using horizontal-to-vertical spectral ratios to construct shear-wave velocity profiles

2020

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Abstract. For seismic hazard assessment and earthquake hypocentre localization, detailed shear-wave velocity profiles are an important input parameter. Here, we present a method to construct a shear-wave velocity profiles for a deep unconsolidated sedimentary layer by using strong teleseismic phases and the ambient noise field. Gas extraction in the Groningen field, in the northern part of the Netherlands, is causing low-magnitude, induced seismic events. This region forms an excellent case study due to the presence of a permanent borehole network and detailed subsurface knowledge. Instead of conventional horizontal-to-vertical spectral ratios (H∕V ratios) from amplitude spectra, we calculate power spectral densities and use those as input for H∕V calculations. The strong teleseisms provide resonance recordings at low frequencies, where the seismic noise field is too weak to be recorded well with the employed geophones and accelerometers. The H∕V ratios of the ambient noise field are compared with several forward modelling approaches to quality check the teleseism-based shear-wave velocity profiles. Using the well-constrained depth of the sedimentary basin, we invert the H∕V ratios for velocity profiles. A close relationship is observed between the H∕V spectral ratios from the ambient noise field, shear-wave resonance frequencies and Rayleigh-wave ellipticity. By processing only five teleseismic events, we are able to derive shear-wave velocities for the deeper sedimentary sequence with a 7 % bias in comparison with the existing detailed velocity model for the Cenozoic sediments overlying the Groningen gas field. Furthermore, a relation between resonance frequency and unconsolidated sediment thickness is derived, to be used in other areas in the Netherlands, where detailed depth maps are not available.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Using horizontal-to-vertical spectral ratios to construct shear-wave velocity profiles

2020

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“…Besides, H/V spectrum peaks are obtained from rayleigh wave polarity analysis (Konno and Ohmachi, 1998;Stanko et al, 2016;Rong et al, 2017). H/V spectrum analysis is considered suitable for rayleigh wave type to conduct the realistic microseismic wave (Tarabusi et al, 2017;Nakamura, 2019).…”

Section: Methodsmentioning

confidence: 99%

“…Therefore, the seismic surface waveform in the basin sediment can be amplified up to 1.5 to 2.0 times greater than the normal recording (Irsyam, 2017;Simanjuntak et al, 2018;Cipta et al, 2018). Furthermore, geomorphological studies of destructive earthquakes show the highest levels of the risk occurring in the basin with alluvial sediment (Nakamura, et al, 2019;Papadopoulos et al, 2020;Ali and Ali, 2020).…”

Section: Introductionmentioning

confidence: 97%

A Microtremor Survey to Identify Seismic Vulnerability Around Banda Aceh Using HVSR Analysis

Simanjuntak

Asnawi

Muksin

et al. 2020

EKW

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Banda Aceh can be categorized as an earthquake-prone city because of the existence of two active segments namely Seulimeum and Aceh. Both segments are considered to provide great potential damage in the future. In this article, we conduct a microtremor survey in the Peukan Bada, sub-part of Banda Aceh city, to learn the vulnerability level and support disaster mitigation plan. A total of 20 sites were measured with a seismometer to record the seismic waveform. The waveform was recorded in 45 minutes with a sampling rate of 100 sps and has analyzed using the horizontal-vertical spectrum ratio (HVSR). The results obtained are the dominant parameters, such as the period with a range of 0 – 0.5s, frequency with a range of 0 – 6 Hz, seismicity vulnerability index with a range of 0.1 – 0.5. The result was relevant to the geological conditions of Peukan Bada that dominated by alluvial rocks and mud sediments. The level of vulnerability (Kg > 1.0) obtained is quite high and proportional to the soil type that can amplify the seismic waveform. The results obtained are expected to be a supporting study of disaster mitigation and understand the geological conditions of Banda Aceh in terms of seismic vulnerability.Abstrak: Banda Aceh dapat dikategorikan sebagai kota rawan gempa karena adanya dua segmen aktif yaitu Seulimeum dan Aceh. Kedua segmen tersebut bisa memberikan potensi kerusakan yang besar di masa mendatang. Pada tulisan ini, kami melakukan survei mikrotremor di Kecamatan Peukan Bada, salah satu sub-wilayah kota Banda Aceh, untuk mempelajari tingkat kerentanan dan mendukung rencana mitigasi bencana. Sebanyak 20 lokasi diukur dengan seismometer untuk merekam bentuk gelombang seismik. Gelombang direkam selama 45 menit dengan jumlah sampel 100 sps dan dianalisis menggunakan horizontal-vertical spectrum ratio (HVSR). Hasil yang diperoleh adalah parameter yang dominan yaitu periode dengan rentang 0 – 0,5s, frekuensi dengan range 0 - 6 Hz, indeks kerentanan kegempaan dengan rentang 0,1 – 0,5. Hasil tersebut relevan dengan kondisi geologi Peukan Bada yang didominasi oleh batuan aluvial dan endapan lumpur. Tingkat kerentanan (Kg > 1,0) yang diperoleh cukup tinggi dan sebanding dengan jenis tanah yang dapat memperbesar gelombang seismik. Hasil yang diperoleh diharapkan dapat menjadi pendukung kajian mitigasi bencana dan memahami kondisi geologi Banda Aceh dari segi kerentanan seismik.

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“…This technique using microtremors recordings from a three-component portable station is one widely applicable technique for estimating local site effects. Igarashi (1970, 1971) discussed the origin of the microtremor is derived from body waves or surface waves (Nakamura 2019), so the root of the method does not come from these studies, it comes from Nakamura (1989) when he debated its capability to estimate the resonance frequency of sedimentary cover. The HVSR method is the most applicable technique for estimation the soft sedimentary cover thickness (e.g.…”

Section: Hvsr Methods (Nakamura Technique)mentioning

confidence: 99%

Estimation of seismic site effect at the new Tiba City proposed extension, Luxor, Egypt

Mohamed

Ali

Mostafa

2020

NRIAG Journal of Astronomy and Geophysics

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The Horizontal-to-Vertical Spectral Ratio (HVSR) technique is one of the most suitable tools for estimating the geological effect on ground motion. The main target of this study is to estimate the site effect and the fragility index value at the new Tiba City proposed extension. To achieve these targets, 21 ambient vibration recordings were conducted with 1 km grid to cover the investigated area. The estimated predominant frequency (f 0) distribution is a relative uniform and occurs at low frequency, ranging from 0.35 to 0.75 Hz and its maximum corresponding amplitude of seismic wave (A 0) starts from 3.1 up to 6.5. The qualitative interpretation of loose sedimentary cover thickness is large (136 to 410 m with average ~270 m) that coincided with occurrence of (f 0) at low level. The fragility index for the ground (K g) at each measured site was computed depending on the estimated H/V amplitude and corresponding (f 0), and found to range from 17 to 118 across the investigated area. The highest values of K g were obviously found in the northeastern part of the proposed site, where the highest amplification factor and the lowest fundamental frequency are found.

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What Is the Nakamura Method?

Cited by 91 publications

References 7 publications

Using horizontal-to-vertical spectral ratios to construct shear-wave velocity profiles

Using horizontal-to-vertical spectral ratios to construct shear-wave velocity profiles

A Microtremor Survey to Identify Seismic Vulnerability Around Banda Aceh Using HVSR Analysis

Estimation of seismic site effect at the new Tiba City proposed extension, Luxor, Egypt

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