
 The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

MEMS (Micro Electro-Mechanical Systems) sensors enable a vast range of applications: among others, the use of MEMS accelerometers for seismology related applications has been emerging considerably in the last decade In this paper, we provide a comprehensive review of the capacitive MEMS accelerometers: from the physical functioning principles, to the details of the technical precautions, and to the manufacturing procedures We introduce the applications within seismology and earth sciences related disciplines, namely: earthquake observation and seismological studies, seismic surveying and imaging, structural health monitoring of buildings Moreover, we describe how the use of the miniaturized technologies is revolutionizing these fields and we present some cutting edge applications that, in the very last years, are taking advantage from the use of MEMS sensors, such as rotational seismology and gravity measurements In a ten-year outlook, the capability of MEMS sensors will certainly improve through the optimization of existing technologies, the development of new materials, and the implementation of innovative production processes In particular, the next generation of MEMS seismometers could be capable of reaching a noise floor under the lower seismic noise (few tenths of ng/ Hz ) and expanding the bandwidth towards lower frequencies (∼001 Hz)

A Review of the Capacitive MEMS for Seismology.

To gain a better insight of the hydrogeology and the location of the main tectonic faults of Stromboli volcano in Italy, we collected electrical resistivity measurements, soil CO2 concentrations, temperature and self-potential measurements along two profiles. These two profiles started at the village of Ginostra in the southwest part of the island. The first profile (4.8 km in length) ended up at the village of Scari in the north east part of the volcano and the second one (3.5 km in length) at Forgia Vecchia beach, in the eastern part of the island. These data were used to provide insights regarding the position of shallow aquifers and the extension of the hydrothermal system. This large-scale study is complemented by two high-resolution studies, one at the Pizzo area (near the active vents) and one at Rina Grande where flank collapse areas can be observed. The Pizzo corresponds to one of the main degassing structure of the hydrothermal system. The main degassing area is localized along a higher permeability area corresponding to the head of the gliding plane of the Rina Grande sector collapse. We found that the self-potential data reveal the position of an aquifer above the villages of Scari and San Vincenzo. We provide an estimate of the depth of this aquifer from these data. The lateral extension of the hydrothermal system (resistivity ∼15-60 ohm m) is broader than anticipated extending in the direction of the villages of Scari and San Vincenzo (in agreement with temperature data recorded in shallow wells). The lateral extension of the hydrothermal system reaches the lower third of the Rina Grande sector collapse area in the eastern part of the island. The hydrothermal body in this area is blocked by an old collapse boundary. This position of the hydrothermal body is consistent with low values of the magnetization (<2.5 A m−1) from previously published work. The presence of the hydrothermal body below Rina Grande raises questions about the mechanical stability of this flank of the edifice.

Hydrogeology of Stromboli volcano, Aeolian Islands (Italy) from the interpretation of resistivity tomograms, self-potential, soil temperature and soil CO2 concentration measurements

Muography consists in observing the differential absorption of muons – elementary particles produced through cosmic-ray interactions in the Earth atmosphere – going through the volcano and can attain a spatial resolution of tens of meters. We present here the first experiment of nuclear emulsion muography at the Stromboli volcano. Muons have been recorded during a period of five months by a detector of 0.96 m2 area. The emulsion films were prepared at the Gran Sasso underground laboratory and were analyzed at Napoli, Salerno and Tokyo scanning laboratories. Our results highlight a significant low-density zone at the summit of the volcano with density contrast of 30–40% with respect to bedrock. The structural setting of this part of the volcanic edifice controls the eruptive dynamics and the stability of the “Sciara del Fuoco” slope, which is affected by recurrent tsunamigenic landslides. Periodical imaging of the summit of the Stromboli volcano such as that provided by muography can become a useful method for studying the evolution of the internal structure of the volcanic edifice.

/pdf/first-muography-of-stromboli-volcano-20uatnghag.pdf

First muography of Stromboli volcano.

http://www.diva-portal.org/smash/get/diva2:872987/FULLTEXT01

Multicomponent broadband digital-based seismic landstreamer for near-surface applications

Aeromagnetic constraints on the subsurface structure of Stromboli Volcano, Aeolian Islands, Italy

A 2D vibroseis line was acquired in the Vienna Basin (Austria) for the purpose of comparing the data of digital multicomponent single sensors based on microelectromechanical system (MEMS) sensors alongside conventional vertical-component geophone arrays. For efficient removal of coherent noise during processing, all source points were recorded in single-sweep mode, i.e., no vertical stacking was performed in the field. On this densely sampled data set, several noise-reduction techniques, such as digital array forming, frequency-wavenumber (f-k) filtering in shot and receiver domains, and polarization filters, proved to be valuable in reducing source-generated noise. The results showed that, with the use of single-sweep recording and polarization filter techniques, it is possible to produce seismic sections for a single-receiver three-component (3C) MEMS line that are comparable to a conventional geophone array line in signal-to-noise ratio. However, the higher number of single geophones and hence the stro...

Evaluation of 3C microelectromechanical system data on a 2D line: Direct comparison with conventional vertical-component geophone arrays and PS-wave analysis

OMV acquired a 2D vibroseis line in the Vienna Basin /Lower Austria with the purpose of comparing digital multi-component single sensors (MEMS) and conventional geophone arrays. The primary exploration target for this line is below 3 km depth. For such deep targets efficient noise reduction is a key element of processing, since signals from these depths are weak and may be totally obscured by the noise cone.

Comparison of single sensor 3C MEMS and conventional geophone arrays for deep target exploration

Geoelectric Surveys to Supplement to Determine the Structure of Hydro-Thermal Systems – Case Study Vulcano

We present a case study for designing a passive seismic monitoring network in a large underground gas storage site. The study included measurements of background seismic noise at selected locations across the site and background seismic noise along a string of receivers cemented in a shallow monitoring borehole. We measured the noise levels over a period of three months and studied the background seismic noise reduction in the shallow monitoring borehole. Specifically this study reveals a significant decrease with depth of the temporal variations in background seismic noise levels at the shallow monitoring borehole relative to the surface. We compare location accuracy from the downhole and surface monitoring arrays, and combinations of these to determine the optimal monitoring array. We also evaluate the detection threshold for microseismic events in the proposed shallow borehole monitoring array based on measured noise levels and empirical observations of microseismic events in similar reservoirs.

C. Stotter

Papers

Aeromagnetic constraints on the subsurface structure of Stromboli Volcano, Aeolian Islands, Italy

Evaluation of 3C microelectromechanical system data on a 2D line: Direct comparison with conventional vertical-component geophone arrays and PS-wave analysis

Comparison of single sensor 3C MEMS and conventional geophone arrays for deep target exploration

Geoelectric Surveys to Supplement to Determine the Structure of Hydro-Thermal Systems – Case Study Vulcano

Design of Passive Seismic Monitoring for Underground Gas Storage in the Vienna Basin, Austria