To define the procedures necessary to unambiguously define the subsurface model, a comprehensive set of active and passive seismic data was collected in an industrial area characterized by an extremely high level of background... more
To define the procedures necessary to unambiguously define the subsurface model, a comprehensive set of active and passive seismic data was collected in an industrial area characterized by an extremely high level of background microtremors. Passive data are recorded to define three observables: the dispersion curve of the vertical component of Rayleigh waves via miniature array analysis of microtremors, the Love-wave dispersion curve via extended spatial autocorrelation, and the horizontal-to-vertical spectral ratio (HVSR). Active data used for the holistic analysis of surface waves are extracted from data recorded through a hybrid acquisition procedure accomplished with only two 3C geophones used to simultaneously define the HVSR at two points. Defined observables are combined according to three different approaches: the joint analysis of Rayleigh waves and HVSR, the joint analysis of Rayleigh and Love waves together with the HVSR, and the joint analysis of multicomponent group velocities together with the HVSR and Rayleigh-wave particle motion (RPM) curves. In agreement with the theory, data indicate that, in general, surface-wave modeling cannot be performed considering modal dispersion curves: dispersion obtained from passive data needs to be modeled considering the effective curve, whereas group velocity obtained from active data can be analyzed using the full velocity spectrum technique. Results indicate that joint inversion of Rayleigh-wave dispersion and HVSR does not necessarily ensure the correctness of the obtained S-wave velocity (𝑉s) profile and that Love waves represent a key observable to fully constrain an unambiguous inversion procedure. However, the joint analysis of multicomponent group velocity spectra (from active multicomponent single-offset data) together with the HVSR and RPM curves is a further efficient way to obtain robust 𝑉s profiles through the active and passive data obtained by a single 3C geophone.
Rainfall-induced landslides pose a significant risk to communities and infrastructures. To improve the prediction of such events, it is imperative to adequately investigate the rainfall-dependent dynamics (leading to fluidization) and any... more
Rainfall-induced landslides pose a significant risk to communities and infrastructures. To improve the prediction of such events, it is imperative to adequately investigate the rainfall-dependent dynamics (leading to fluidization) and any associated internal sliding along shear planes within clayey slopes. Therefore, the present study adopted ambient noise analysis based on the Horizontal to Vertical Spectral Ratio (HVSR) method, to measure the seasonal variation of Rayleigh wave ellipticity as an indicator for the internal deformation and transition in the material state. The methodology was applied to an existing landslide, where variations in soil stiffness and internal sliding were expected to occur in response to rainfall. To improve the interpretation of the HVSR results (and hence the prediction of landslide’ reactivation by rainfall), HVSR measurements were also conducted on a field-scale pile load test. The pile test allowed a comparison of the seismic data generated by the...
The city of Ivanec is located between valley of the Bednja River and Mt. Ivanščica and this area can be prone to significant seismic site amplification due to local site characteristics. This study presents the first assessment of seismic... more
The city of Ivanec is located between valley of the Bednja River and Mt. Ivanščica and this area can be prone to significant seismic site amplification due to local site characteristics. This study presents the first assessment of seismic site amplification for the city of Ivanec by the microtremor horizontal-to-vertical-spectral-ratio (HVSR) method and the equivalent-linear (EQL) site response analysis. Based on microtremor measurements and HVSR analysis, fundamental soil frequency and HVSR peak amplitude maps indicate potentially seismic danger zones. The 1-D EQL site response analysis was performed using multiple suites of earthquake ground motions scaled to the 95- and 475-year return periods of peak ground accelerations. Site amplification maps at the predominant peak frequency and ground surface indicate two microzones, one with high amplification in the central part of the city due to soft soil characteristics, and the other with small amplification in the transitional zone f...
Introduction. The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al., 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al., 2014) and to identify areas with similar seismic... more
Introduction. The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al., 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al., 2014) and to identify areas with similar seismic behaviour. Theoretical considerations (Nakamura, 1989) and experimental tests showed that amplification of horizontal motions between bottom and top of a sedimentary cover is well related to the ratio between the spectra of the horizontal and vertical components of the ground velocity (Nakamura, 2000). This ratio is a measure of ellipticity of Rayleigh wave polarization, overlooking Love and body waves contribution. Assuming that subsoil can be represented as a stack of homogeneous horizontal layers and imposing some geometric and/or physical constraints it is possible to estimate the parameters of the shear wave velocity model (Fäh et al., 2003; Parolai et al., 2000). The integration of data related to HVSR and active techniques based on the analysis of s...
For the seismic and dynamic design of the civil eng ineering projects a significant role is assumed by the geotechnical-seismic characterization of the site. The new Italian seismic code as well as the Eurocod es and other international... more
For the seismic and dynamic design of the civil eng ineering projects a significant role is assumed by the geotechnical-seismic characterization of the site. The new Italian seismic code as well as the Eurocod es and other international seismic codes require the seismic sit e classification made on the basis of the shear wav e velocity profile. Among the several techniques of site inves tigation the MASW method (Multichannel Analysis of Surface Waves) and the ReMi method (Refraction Microtremors ) allow the determination of the shear wave velocit y profile and hence the seismic site classification by means of the measurement and the consequent analysis of t he Rayleigh waves. The article proposes a joint application of b th the active MASW and the ReMi to a real case in order to compare the two complementary methods.
The Yogyakarta earthquake in 2006 caused damage in several areas, especially in the area of Klaten Regency. As a result, many infrastructures, houses, health facilities and casualties have been damaged. The research was conducted with the... more
The Yogyakarta earthquake in 2006 caused damage in several areas, especially in the area of Klaten Regency. As a result, many infrastructures, houses, health facilities and casualties have been damaged. The research was conducted with the target of knowing the level of earth's hazard by microzoning soil vulnerability areas in the Bayat District, Klaten, Central Java. This study used the microseismic method with the HVSR (Horizontal to Vertical Spectral Ratio) analysis method. Where are the natural/dominant frequency parameters, natural amplification, and earthquake vulnerability index as measured parameters? This study aims to carry out microzonation of disaster vulnerability risks which are interpreted from the results obtained, namely amplification maps (A0), dominant frequency (f0), earthquake vulnerability (Kg), and shear wave velocity maps at a depth of 30 meters (Vs30). Data acquisition was carried out at 19 measurement points with a spacing between points having a distanc...
• Generalità: onde di Rayleigh e Love, P e S, velocità di fase e gruppo • Sezioni 2D oltre la rifrazione: 2D-SuPPSALA (e non solo) • HVSR: identificazione e rimozione di segnali industriali • Amplificazioni e rimozione di segnali... more
• Generalità: onde di Rayleigh e Love, P e S, velocità di fase e gruppo • Sezioni 2D oltre la rifrazione: 2D-SuPPSALA (e non solo) • HVSR: identificazione e rimozione di segnali industriali • Amplificazioni e rimozione di segnali industriali • Amplificazioni: HVSR versus SSR e SSRn • Esempi di analisi Holisurface®, ESAC multi-componente con array lineari, MAAM e DownHole
The 7.5 Mw tectonic earthquake that hit Palu City on 28 September 2018 was followed by tsunami and liquefaction, triggered massive mudflows in Balaroa, Petobo, and Jono Oge areas. This study focuses on the generating factors of... more
The 7.5 Mw tectonic earthquake that hit Palu City on 28 September 2018 was followed by tsunami and liquefaction, triggered massive mudflows in Balaroa, Petobo, and Jono Oge areas. This study focuses on the generating factors of liquefaction such as the condition of soil lithology, depth of water table, the distance to the focal mechanism, and the thickness of soft sediment. Microtremor data, including the Horizontal Vertical Spectral Ratio (HVSR), geological condition, and borehole data, were examined to conduct the liquefaction analysis. The analysis results based on the microtremor data showed that the distribution of ground shear strain values in Palu City ranged from 0.75 × 10–4 to 2.56 × 10–4. The distribution of the locations of the liquefaction was correlated to the distribution of ground shear strain values. High ground shear strain values and a shallow groundwater level were discovered in Palu City valley, which indicates that liquefaction in Palu City will undoubtedly occu...
The upwelling of fluids, subject to overpressure, along with discontinuities in the subsoil, causes the formation of geological structures known as mud volcanoes. These structures, very widespread in the world and in some cases located... more
The upwelling of fluids, subject to overpressure, along with discontinuities in the subsoil, causes the formation of geological structures known as mud volcanoes. These structures, very widespread in the world and in some cases located near inhabited centers, can represent a considerable risk factor for the population, as they can give rise to paroxysmal eruptions, even very violent. The assessment of the characteristics and structure of the subsoil of the areas affected by this phenomenon can prove to be a useful tool for risk mitigation. Non-invasive geophysical surveys were carried out in the area of the active cone of the Santa Barbara mud volcano in order to obtain a 3D characterization of the subsoil. Through the processing and integration of data derived from active and passive seismic surveys was obtained, a 3D model showing the seismostratigraphic subsoil structure. The electrical resistivity tomography surveys provided results comparable to those obtained from seismic surv...
Il presente lavoro è teso a riportare le attività relative alle indagini in foro Down Hole volte al fine di identificare la risposta sismica e le velocità di propagazione delle onde sismiche P ed S nel sottosuolo di P. zza Leonardo sita... more
Il presente lavoro è teso a riportare le attività relative alle indagini in foro Down Hole volte al fine di identificare la risposta sismica e le velocità di propagazione delle onde sismiche P ed S nel sottosuolo di P. zza Leonardo sita nel Comune di Napoli. L'attività è ...
El objetivo de este trabajo es obtener secciones sísmicas para delimitar estructuras geológicas asociadas a yacimientos de hidrocarburos. Utilizamos datos de sísmica pasiva de un arreglo rectangular localizado al noreste de la República... more
El objetivo de este trabajo es obtener secciones sísmicas para delimitar estructuras geológicas asociadas a yacimientos de hidrocarburos. Utilizamos datos de sísmica pasiva de un arreglo rectangular localizado al noreste de la República Mexicana y el método de Interferometría Sísmica (IS), el cual permite extraer la función de Green mediante el uso de correlaciones cruzadas (CC(t)) de trazas de ruido sísmico. Procesamos 6 líneas de 8 km de longitud aproximadamente, con 159 geófonos cada una. Las CC(t) obtenidas (también llamadas pseudo-secciones sísmicas de tiros virtuales) fueron procesadas para la extracción de información estructural y de velocidad subsuperficial, con los algoritmos que usualmente son utilizados en la industria de la sismología de exploración. Los resultados los reagrupamos en grupos de offset común (Common Offset Gathers, por sus siglas en ingles COG), para generar imágenes del campo de velocidades en el subsuelo en términos de secciones sísmicas de offset cero....
We present the results of the analysis of vertical component from earthquake and seismic noise records obtained in the Sabana de Bogot. to determine subsoil structure in that region. Rayleigh waves present in the earthquake data were... more
We present the results of the analysis of vertical component from earthquake and seismic noise records obtained in the Sabana de Bogot. to determine subsoil structure in that region. Rayleigh waves present in the earthquake data were processed to estimate to estimate group velocities. In the case of seismic noise, we used seismic interferometry to estimate Green’s functions between stations from average cross-correlation. Rayleigh wave pulses were recovered between stations from seismic noise. We processed the results to estimate group velocities in all cases. The results show the impact of geology on group velocities in the studied region. Different station pairs show varying group velocities depending on the age of the rocks along the paths. Our estimated impedance contrast between surficial deposits and underlying bedrock suggests possible amplification of ground motion larger than a factor of 10. The poor quality and the limited quantity of our data limited the comprehensiveness of our results. The frequency ranges of the results showed poor overlap, hindering comparisons among paths. In spite of their limitations, our results highlight the importance of site effects in the Sabana de Bogot. and the need to take them into account to estimate ground motion for future events in that region.
This paper aims to obtain compressional body waves (seismic sections) to delimit geological structures associated with hydrocarbon reservoirs. We used a passive seismic dataset from a rectangular array located at northeast of Mexico.... more
This paper aims to obtain compressional body waves (seismic sections) to delimit geological structures associated with hydrocarbon reservoirs. We used a passive seismic dataset from a rectangular array located at northeast of Mexico. Seismic Interferometry (IS) method, which allows extracting the Green’s function by using cross-correlations (CC(t)) of seismic traces was applied. We processed six lines of approximately 8 km length, with 159 geophones each. The obtained CC(t) (also called virtual shots pseudo-sections) were processed with the algorithms that generally are used in the seismic exploration industry to extract the structural and sub-surface velocity information. We regrouped the results of the pseudo-sections of virtual shots by common offset gathers (COG) to generate subsurface images in terms of a zero-offset seismic section. Although, alternative processing algorithms were performed, which consists in applying the wavelet transform method to decompose and reconstruct the CC(t) by means of the Meyer wavelet, improving the quality of the CC(t). Subsequently, new seismic sections were generated considering a common offset. We use offsets of 100, 500, 900, 1300, 1700, and 2100 m among source-receiver virtual arrays. In this case, results were improved substantially, clearly showing the expected reflectors. We observed that the depth of investigation increases for higher offsets, meanwhile the surface resolution decreases. The sections were stacked with the different offsets mentioned above for each line, resulting in a total common offset section. Finally, the obtained sections were compared versus a conventional seismic section (also called “active” seismic sections) migrated in depth.
Introduction. The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al., 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al., 2014) and to identify areas with similar seismic... more
Introduction. The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al., 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al., 2014) and to identify areas with similar seismic behaviour. Theoretical considerations (Nakamura, 1989) and experimental tests showed that amplification of horizontal motions between bottom and top of a sedimentary cover is well related to the ratio between the spectra of the horizontal and vertical components of the ground velocity (Nakamura, 2000). This ratio is a measure of ellipticity of Rayleigh wave polarization, overlooking Love and body waves contribution. Assuming that subsoil can be represented as a stack of homogeneous horizontal layers and imposing some geometric and/or physical constraints it is possible to estimate the parameters of the shear wave velocity model (Fäh et al., 2003; Parolai et al., 2000). The integration of data related to HVSR and active techniques based on the analysis of s...
Authors have calculated the H/V spectral ratios using seismic-noise recordings in the uppermost layers north of the Seymour-Marambio Island, Antarctic. Sixty-seven seismic site-response measurements near and far from the Argentinean... more
Authors have calculated the H/V spectral ratios using seismic-noise recordings in the uppermost layers north of the Seymour-Marambio Island, Antarctic. Sixty-seven seismic site-response measurements near and far from the Argentinean Marambio Base runway suggest geotechnical works on the uppermost sedimentary layers due to maintenance, landing, and taxi of large loads and aircraft during decades could contribute to changes in their seismic dynamic response. Two horizontal images of Vp, Vs, and Vp/ Vs ratios at 1.0 m and 35.0 m depth show lateral variations in the permafrost properties. Authors interpret that permafrost is emplaced in rocks with different porosities and contrasting fluids saturation at those depths. In shallow strata, the saturation of gases affects mainly the elastic properties. In deeper strata, where the location of water reservoirs is detected, the primary mechanism of seismic dissipation is anelastic.
Authors have calculated the H/V spectral ratios using seismic-noise recordings in the uppermost layers north of the Seymour-Marambio Island, Antarctic. Sixty-seven seismic site-response measurements near and far from the Argentinean... more
Authors have calculated the H/V spectral ratios using seismic-noise recordings in the uppermost layers north of the Seymour-Marambio Island, Antarctic. Sixty-seven seismic site-response measurements near and far from the Argentinean Marambio Base runway suggest geotechnical works on the uppermost sedimentary layers due to maintenance, landing, and taxi of large loads and aircraft during decades could contribute to changes in their seismic dynamic response. Two horizontal images of Vp, Vs, and Vp/ Vs ratios at 1.0 m and 35.0 m depth show lateral variations in the permafrost properties. Authors interpret that permafrost is emplaced in rocks with different porosities and contrasting fluids saturation at those depths. In shallow strata, the saturation of gases affects mainly the elastic properties. In deeper strata, where the location of water reservoirs is detected, the primary mechanism of seismic dissipation is anelastic.
Suatu wilayah yang memiliki kondisi geologi yang sama dapat memberikan respon yang berbeda terhadap efek getaran tanah, bergantung pada karakteristik batuan penyusun formasi di wilayah itu. Fenomena ini disebut site effect. Spektra... more
Suatu wilayah yang memiliki kondisi geologi yang sama dapat memberikan respon yang berbeda terhadap efek getaran tanah, bergantung pada karakteristik batuan penyusun formasi di wilayah itu. Fenomena ini disebut site effect. Spektra ambient noise yang diperoleh dari pengukuran mikrotremor dapat digunakan untuk menentukan respon suatu site khususnya frekuensi dominan lapisan sedimen. Respon frekuensi ini berhubungan dengan ketebalan lapisan sedimen. Berdasarkan formasi geologinya, Kota Palu tersusun atas endapan aluvium berumur holosen yang menjadi sedimen penyusun paling muda di wilayah tersebut. Penelitian ini bertujuan untuk memperoleh estimasi ketebalan lapisan sedimen di tiga titik pengukuran mikrotremor dari nilai spektrum horizontal to vertical () yang merempresentasi frekuensi dominan (f0) serta kecepatan gelombang geser (Vs) lapisan sedimen. Hasil yang diperoleh memperlihatkan nilai frekuensi dominan tanah f0 <2.5 Hz, hasil inversi kurva HVSR memperlihatkan variasi ketebal...
The Yogyakarta earthquake in 2006 caused damage in several areas, especially in the area of Klaten Regency. As a result, many infrastructures, houses, health facilities and casualties have been damaged. The research was conducted with the... more
The Yogyakarta earthquake in 2006 caused damage in several areas, especially in the area of Klaten Regency. As a result, many infrastructures, houses, health facilities and casualties have been damaged. The research was conducted with the target of knowing the level of earth's hazard by microzoning soil vulnerability areas in the Bayat District, Klaten, Central Java. This study used the microseismic method with the HVSR (Horizontal to Vertical Spectral Ratio) analysis method. Where are the natural/dominant frequency parameters, natural amplification, and earthquake vulnerability index as measured parameters? This study aims to carry out microzonation of disaster vulnerability risks which are interpreted from the results obtained, namely amplification maps (A0), dominant frequency (f0), earthquake vulnerability (Kg), and shear wave velocity maps at a depth of 30 meters (Vs30). Data acquisition was carried out at 19 measurement points with a spacing between points having a distanc...
Based on BNPB data, there has been landslide disaster due to abrasion that caused bridge and houses collapse in Amurang, South Minahasa on June 15, 2022. On geological map, the Amurang area classified as volcanic rock that is suspected to... more
Based on BNPB data, there has been landslide disaster due to abrasion that caused bridge and houses collapse in Amurang, South Minahasa on June 15, 2022. On geological map, the Amurang area classified as volcanic rock that is suspected to be Tondano's Tuff when it exploded and formed Tondano's Caldera. BMKG, in this case the Manado Geophysics Station, conducted a microtremor survei and analysed the data of the survei results using the Horizontal to Vertical Spectral Ratio (HVSR) method. This method can determine the value of the natural frequency and amplification of the soil which can be used to classify the soil at the survei location. The result show that the disaster area in Amurang is an alluvial rock formation formed from deltaic sedimentation, topsoil, mud, etc. with a depth of 30 meters or more. It does not match the classification given by the 1997 geological map.
Landslides (LS) represent geomorphological processes that can induce changes over time in the physical, hydrogeological, and mechanical properties of the involved materials. For geohazard assessment, the variations of these properties... more
Landslides (LS) represent geomorphological processes that can induce changes over time in the physical, hydrogeological, and mechanical properties of the involved materials. For geohazard assessment, the variations of these properties might be detected by a wide range of non-intrusive techniques, which can sometimes be confusing due to their significant variation in accuracy, suitability, coverage area, logistics, timescale, cost, and integration potential; this paper reviews common geophysical methods (GM) categorized as Emitted Seismic and Ambient Noise based and proposes an integrated approach between them for improving landslide studies; this level of integration (among themselves) is an important step ahead of integrating geophysical data with remote sensing data. The aforementioned GMs help to construct a framework based on physical properties that may be linked with site characterization (e.g., a landslide and its subsurface channel geometry, recharge pathways, rock fragments...
Suatu wilayah yang memiliki kondisi geologi yang sama dapat memberikan respon yang berbeda terhadap efek getaran tanah, bergantung pada karakteristik batuan penyusun formasi di wilayah itu. Fenomena ini disebut site effect. Spektra... more
Suatu wilayah yang memiliki kondisi geologi yang sama dapat memberikan respon yang berbeda terhadap efek getaran tanah, bergantung pada karakteristik batuan penyusun formasi di wilayah itu. Fenomena ini disebut site effect. Spektra ambient noise yang diperoleh dari pengukuran mikrotremor dapat digunakan untuk menentukan respon suatu site khususnya frekuensi dominan lapisan sedimen. Respon frekuensi ini berhubungan dengan ketebalan lapisan sedimen. Berdasarkan formasi geologinya, Kota Palu tersusun atas endapan aluvium berumur holosen yang menjadi sedimen penyusun paling muda di wilayah tersebut. Penelitian ini bertujuan untuk memperoleh estimasi ketebalan lapisan sedimen di tiga titik pengukuran mikrotremor dari nilai spektrum horizontal to vertical () yang merempresentasi frekuensi dominan (f0) serta kecepatan gelombang geser (Vs) lapisan sedimen. Hasil yang diperoleh memperlihatkan nilai frekuensi dominan tanah f0 <2.5 Hz, hasil inversi kurva HVSR memperlihatkan variasi ketebal...
Il presente lavoro è teso a riportare le attività relative alle indagini in foro Down Hole volte al fine di identificare la risposta sismica e le velocità di propagazione delle onde sismiche P ed S nel sottosuolo di P. zza Leonardo sita... more
Il presente lavoro è teso a riportare le attività relative alle indagini in foro Down Hole volte al fine di identificare la risposta sismica e le velocità di propagazione delle onde sismiche P ed S nel sottosuolo di P. zza Leonardo sita nel Comune di Napoli. L'attività è ...
