Microtremor

The present data are subsurface velocity structures retrieved by applying the theory of diffuse field concept to the strong motion data of earthquakes observed at 1744 sites of K-NET and KiK-net (operated by the National Institute of Earth Science and Disaster Resilience) in Japan. Additionally, the data include peak fundamental and predominant frequencies as identified from the observed and theoretical horizontal-to-vertical spectral ratios for earthquakes (eHVSR). Based on our novel proposed quarter wavelength approach, we could define the effective bedrock depths and correlate them with the corresponding peak frequencies...

In this study, we provide a detailed analysis of entropy measures calculated for fixation eye movement trajectories from the three different datasets. We employed six key metrics (Fuzzy, Increment, Sample, Gridded Distribution, Phase, and Spectral Entropies). We calculate these six metrics on three sets of fixations: (1) fixations from the GazeCom dataset, (2) fixations from what we refer to as the "Lund" dataset, and (3) fixations from our own research laboratory ("OK Lab" dataset). For each entropy measure, for each dataset, we closely examined the 36 fixations with the highest entropy and the 36 fixations with the lowest entropy...

In the process of coal mining, prevention and control of water hazard is essential. It is the precondition for water hazard control to detect and determine the distribution of underground water-conducting channels. In urban environments, traditional methods such as active source seismic exploration and transient electromagnetic exploration commonly used in the field are difficult to carry out effectively due to various factors. In this paper, the microtremor survey method (MSM) and the opposing coils transient electromagnetic method (OCTEM) are adapted to conduct the surface exploration of the coal mine water-conducting channels in the urban environment...

The data presented contains a collection of microtremor measurement data regarding the structures and fluid flow of the Mt. Telomoyo's geothermal manifestation, Indonesia. The data are primary data taken using 3 unit single-station microtremor devices with a total of 60 acquisition stations in The Umbul Temple, Dukuh Temple and Pakis Dadu hot spring manifestation area. Data was obtained using 3-component digital seismograph VHL PS-2B series and recorded with a data logger type GL 240 with a duration of 10 min...

The dataset provided in this paper includes the lateral vibration data obtained by on-site vibration tests on an 18-story timber-concrete hybrid building, which was completed in 2017 and is located within the University of British Columbia campus in Vancouver, Canada. Aiming at evaluating vibration properties such as natural periods, damping ratios, and mode shapes, microtremor measurement (i.e., ambient vibration test) and human-powered excitation tests were conducted from March 27th to 29th , 2023. Lateral velocity data of the building were collected using eight servo velocity sensors, type VSE-15D, and a data acquisition system, type SPC-52, composed of an A/D converter and a DC amplifier...

Ocular microtremor (OMT) is the smallest of three involuntary fixational micro eye movements, which has led to it being under researched in comparison. The link between OMT and brain function generates a strong rationale for further study as there is potential for its use as a biomarker in populations with neurological injury and disease. This structured review focused on populations previously studied, instrumentation used for measurement, commonly reported OMT outcomes, and recommendations concerning protocol design and future studies...

The data presented contains a collection of microtremor measurement data in the Kaligarang Fault zone, Indonesia. This study aims to present data regarding the structure and lithology of the rocks in the Kaligarang Fault zone. Data was obtained using a triaxial geophone VHL PS 2B and recorded with a data logger type GL 240 with a duration of 10 minutes. The data in this study are primary data taken using a single-station microtremor device with a total of 75 acquisition points in the Kaligarang Fault zone. This data can then be used in the analysis of the Horizontal to Vertical Spectral Ratio (HVSR) which will later produce the hv curve...

Microtremor recording tests using an accelerometer were carried out in this paper with the aim of characterizing the effects of seasonally frozen soil on the seismic site response, including the two-direction microtremor spectrum, site predominant frequency, and site amplification factor. The study selected eight typical seasonal permafrost sites in China for site microtremor measurements during both summer and winter seasons. Based on the recorded data, the horizontal and vertical components of the microtremor spectrum, HVSR curves, site predominant frequency, and site amplification factor were calculated...

Active fault detection has an important significance for seismic disaster prevention and mitigation in urban areas. The high-density station arrays have the potential to provide a microtremor survey solution for shallow seismic investigations. However, the resolution limitation of the nodal seismometer and small-scale lateral velocity being inhomogeneous hinder their application in near-surface active fault exploration. Distributed acoustic sensing (DAS) has been developed rapidly in the past few years; it takes an optical fiber as the sensing medium and signal transmission medium, which can continuously detect vibration over long distances with high spatial resolution and low cost...

INTRODUCTION: Optical Coherence Tomography Angiography (OCTA) is a new non-invasive imaging modality that gains increasing popularity for the observation of the microvasculatures in the retina and the conjunctiva, assisting clinical diagnosis and treatment planning. However, poor imaging quality, such as stripe artifacts and low contrast, is common in the acquired OCTA and in particular Anterior Segment OCTA (AS-OCTA) due to eye microtremor and poor illumination conditions. These issues lead to incomplete vasculature maps that in turn makes it hard to make accurate interpretation and subsequent diagnosis...

The development and utilization of urban underground space depend heavily on an understanding of urban geological conditions. The microtremor survey method is essential in urban geological surveys due to its quickness, convenience, non-destructiveness, and interference resistance. Since only the fundamental dispersion curves of Rayleigh waves can be obtained by utilizing the spatial autocorrelation method, the inversion results have multiple solutions. To improve the accuracy of the microtremor survey, this study employed the frequency-Bessel transform to extract the fundamental and higher modes of dispersion information of Rayleigh waves from the microtremor data array and verified the effectiveness of this method by synthesizing theoretical microtremor signals...

The most permanent magnets in current electromagnetic velocity sensors are magnet cylinders that have been axially magnetized, with magnetic boots changing the propagation direction of the magnetic induction lines of the magnet cylinders. However, the magnetic field generated by the magnet cylinders is not fully utilized, which leads to uneven magnetic field intensity of the working air-gap and high magnetic field intensity of the nonworking air-gap. We propose a novel dual-magnet structure (DM) mainly consisting of two magnet loops that are magnetized radially and a magnetic conductive shaft, adopting a concentric nested configuration...

Identifying cliffs that are prone to fall and providing a sufficient lead time for rockfall warning are crucial steps in disaster risk reduction and preventive maintenance work, especially that led by local governments. However, existing rockfall warning systems provide uncertain rockfall location forecasting and short warning times because the deformation and cracking of unstable slopes are not sufficiently detected by sensors before the rock collapses. Here, we introduce ground microtremor signals for early rockfall forecasting and demonstrate that microtremor characteristics can be used to detect unstable rock wedges on slopes, quantitatively describe the stability of slopes and lengthen the lead time for rockfall warning...

The single-station microtremor horizontal-to-vertical spectral ratio (MHVSR) method was initially proposed to retrieve the site amplification function and its resonance frequencies produced by unconsolidated sediments overlying high-velocity bedrock. Presently, MHVSR measurements are predominantly conducted to obtain an estimate of the fundamental site frequency at sites where a strong subsurface impedance contrast exists. Of the earthquake site characterization methods presented in this special issue, the MHVSR method is the furthest behind in terms of consensus towards standardized guidelines and commercial use...

BACKGROUND: Essential tremor is the most prevalent movement disorder and is thought to be caused by abnormalities in the cerebellar system; however, its underlying neural mechanism is poorly understood. In this study, we found that mice lacking netrin-G2, a cell adhesion molecule which is expressed in neural circuits related to the cerebellar system, exhibited a microtremor resembling an essential tremor. However, it was difficult to quantify microtremors in netrin-G2 KO mice. NEW METHOD: We developed a new tremor detector which can quantify the intensity and frequency of a tremor...

The liquefaction at Petobo, Central Sulawesi affected at least 1.8 square kilometers, destroyed up to 744 houses, and caused more than 104 casualties. The data offered in this article are microtremor measurement datasets at the liquefaction site of Petobo, Central Sulawesi, Indonesia. The datasets were recorded using 3 component (3C) Guralp 6T-D broadband seismometer. There are 14 microtremor datasets, which consist of 10 datasets measured inside the liquefaction affected site and 4 datasets recorded outside the liquefaction affected site of Petobo, Central Sulawesi...

BACKGROUND: Superior oblique myokymia (SOM) is a rare disorder characterized by episodic microtremor of the eyeball. in patients with SOM, intermittent contraction of the superior oblique muscle causes irregular and rotatory eye movement, causing oscillopsia and diplopia. Microvascular decompression (MVD) of the trochlear nerve is potentially a definitive treatment method for SOM; however, owing to its rarity, this disorder is not well-known to neurosurgeons, and thus the optimal surgical approach has not yet been determined...

The microtremor survey method (MSM) has the potential to be an important geophysical method for identifying the strata velocity structure and detecting the buried fault structures. However, the existing microtremor exploration equipment has been unable to satisfy the requirements of the MSM, which suffers from low data accuracy, long measurement time, and blind acquisition. In this study, we combined a 2 Hz moving coil geophone with advanced acquisition systems to develop a new integrated energy-efficient wireless sensor node for microtremor exploration...

The seismic hazard and risk analysis for the onshore Groningen gas field requires information about local soil properties, in particular shear-wave velocity ( V S ). A fieldwork campaign was conducted at 18 surface accelerograph stations of the monitoring network. The subsurface in the region consists of unconsolidated sediments and is heterogeneous in composition and properties. A range of different methods was applied to acquire in situ V S values to a target depth of at least 30 m. The techniques include seismic cone penetration tests (SCPT) with varying source offsets, multichannel analysis of surface waves (MASW) on Rayleigh waves with different processing approaches, microtremor array, cross-hole tomography and suspension P-S logging...

We report on the combined far-field measurement of the three involuntary eye movements, drift, microsaccades, and ocular microtremor (OMT), using a noncontact far-field optical method. We review the significance of the smallest and least measured, and thus least understood, of the three, OMT. Using modern digital imaging techniques, we perform detailed analysis, present experimental results, and examine the extracted parameters using a noncontact far-field sensor. For the first time, in vivo noncontact measurements of all fixational in-plane movements of the human eye are reported, which simultaneously provide both the horizontal (left-right) and vertical (up-down) displacement results...