scholarly journals Underground earth strain and seismic radiation measurements with a laser interferometer and a dense small-aperture seismic array

1997 ◽  
Vol 40 (5) ◽  
Author(s):  
A. Amoruso ◽  
L. Crescentini ◽  
G. De Luca ◽  
R. Scarpa ◽  
M. Abril ◽  
...  
Keyword(s):  
Laser Interferometer ◽  
High Sensitivity ◽  
Seismic Array ◽  
Seismic Zone ◽  
Small Aperture ◽  
Short Period ◽  
Physics Laboratories ◽  
Underground Physics ◽  
Very High ◽  
Radiation Measurements

This paper describes two geophysical instruments, installed in the underground physics laboratories of Gran Sasso (LNGS-INFN), located in the seismic zone of the Central Apennines, Italy. These instruments monitor strain and seismic radiation with very high sensitivity: one is a 90 m-long laser interferometer, sensitivity 3 x 10-12, frequency response 10-7-10-2 Hz, and has been operating since 1994. The other is a small-aperture seismic array composed of 21 three-component short period (Mark L4C-3D) and 3 broadband (Guralp CMG-3ESP) seismometers. This dense array will be in operation at the beginning of 1998.

Implementation of array analysis on seismic signals from volcanoes in Iceland recorded on the small-aperture HEKSISZ array

2020 ◽  
Author(s):  
Tim Sonneman ◽  
Kristín Vogfjörd ◽  
Christopher Bean ◽  
Benedikt Halldórsson ◽  
Johannes Schweitzer
Keyword(s):  
Data Analysis ◽  
Real Time ◽  
Seismic Array ◽  
Raspberry Pi ◽  
Seismic Zone ◽  
Seismic Signals ◽  
Secondary Phases ◽  
Small Aperture ◽  
Array Data ◽  
Single Station

<p>We present preliminary results and progress updates of ongoing work at the Icelandic Meteorological Office carried out within the EUROVOLC work package on Volcano pre-eruptive unrest detection schemes. Our main goal is improved understanding of volcanic systems and fracture zones in South Iceland. This requires enhanced detection and mapping capabilities of seismic events from volcanoes in the Eastern Volcanic Zone (EVZ) and faults in the South Iceland Seismic Zone (SISZ), including continuous real-time analysis of seismic signals associated with magma movement in volcanoes and activity on faults in South Iceland. The chosen measures to achieve these tasks are the deployment of a seismic array at the intersection between the EVZ and the SISZ, the implementation of appropriate real-time array data processing and the investigation of spatiotemporal seismic source characteristics such as tracking of magma movements and intrusions from deep to shallow levels in the crust to image the volcanoes’ plumbing systems, shallow caldera seismicity, and earthquake rupture propagation and microseismicity on nearby tectonic faults. Through funding from an Icelandic infrastructure grant and cooperation between IMO and DIAS, the HEKSISZ small-aperture seismic array is being installed about 6 km south of Hekla. The array, which will consist of 12 stations (7 broadband seismometers and at least 5 additional Raspberry PI seismometers and some co-located accelerometers), builds upon experience gained from temporary array operations in the FUTUREVOLC project and will be the first permanent seismic array in Iceland. The array is surrounded by four different volcanic systems and a prominent fracture zone, providing an abundance of seismicity for analysis. The detection of volcanic and local earthquake events depends on signal coherency and the algorithms used. The signal coherency is mainly affected by array geometry and the site and noise conditions. To analyze the wavefield we will use algorithms such as beamforming, signal-to-noise triggers, FK analysis, and cross-correlation on both vertical and horizontal channels. The implementation is through free open-source software, based mainly on Python obspy and further extensions. While the array is still in the process of coming online, we use data from its existing central permanent network station, MJO to analyze signals from the volcanoes and faults in preparation for the future array data analysis. Relevant single-station observations are first arrival polarization and search for existence and timing of secondary phases, such as surface and Moho reflections from different distances and depths. These observed peculiarities will guide the focus of the array data analysis, specifically as one of the main interests is the depth determination of magma movements and intrusions below Hekla. The volcanic region may have strong lateral crustal heterogeneities, so if significant azimuthal deviations are estimated from the single-station analysis, correction parameters for the array will need to be constrained as well. To further test how a future array might perform in this location, we invert synthetic sources at various depths and distances and also use observed source arrays to search for additional phases from possible conversions and reflections and measure their phase velocities.</p>

scholarly journals Modeling heavy metal release in the epiphytic lichen Evernia prunastri

2021 ◽  
Author(s):  
Andrea Vannini ◽  
Luca Paoli ◽  
Riccardo Fedeli ◽  
Sharon Kwambai Kangogo ◽  
Massimo Guarnieri ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Remote Area ◽  
Metal Release ◽  
Evernia Prunastri ◽  
Epiphytic Lichen ◽  
Pollution Levels ◽  
Short Period ◽  
High Pollution ◽  
Heavy Metal Release ◽  
Very High

AbstractIn this study, the release of Cu2+ and Zn2+ was investigated and modeled in the epiphytic lichen Evernia prunastri. Samples were incubated with solutions containing these metals at ecologically relevant concentrations (10 and 100 μM) and then transplanted to a remote area and retrieved after 1, 2, 3, 6, 12, and 18 months. The results showed that, after 12 months, all samples faced similar metal reductions of ca. 80–85%, but after this period, all the involved processes seem to be no longer capable of generating further reductions. These results suggest that the lichen E. prunastri can provide information about environmental improvements after exposure to high or very high pollution levels in a relatively short period of time.

Very high sensitivity optical modulators based on band filling effect in GaInAs quantum wells

1990 ◽  
Author(s):  
T.Y. Chang ◽  
J.E. Zucker ◽  
K.L. Jones ◽  
N.J. Sauer ◽  
B. Tell ◽  
...  
Keyword(s):  
Quantum Wells ◽  
High Sensitivity ◽  
Optical Modulators ◽  
Band Filling ◽  
Very High

Detection of ultraweak signals on the Mikhnevo small-aperture seismic array by using cross-correlation of waveforms

2015 ◽  
Vol 460 (2) ◽  
pp. 189-191 ◽  
Author(s):  
V. V. Adushkin ◽  
I. O. Kitov ◽  
N. L. Konstantinovskaya ◽  
K. S. Nepeina ◽  
M. A. Nesterkina ◽  
...  
Keyword(s):  
Cross Correlation ◽  
Seismic Array ◽  
Small Aperture

P-wave backazimuth anomalies observed by a small-aperture seismic array at Pinyon Flat, southern California: Implications for structure and source location

1996 ◽  
Vol 86 (2) ◽  
pp. 470-476 ◽  
Author(s):  
Cheng-Horng Lin ◽  
S. W. Roecker
Keyword(s):  
Southern California ◽  
Seismic Array ◽  
P Wave ◽  
Small Aperture ◽  
Data Set ◽  
Single Interface ◽  
Seismic Networks ◽  
Dense Seismic Array ◽  
Beamforming Technique

Abstract Seismograms of earthquakes and explosions recorded at local, regional, and teleseismic distances by a small-aperture, dense seismic array located on Pinyon Flat, in southern California, reveal large (±15°) backazimuth anomalies. We investigate the causes and implications of these anomalies by first comparing the effectiveness of estimating backazimuth with an array using three different techniques: the broadband frequency-wavenumber (BBFK) technique, the polarization technique, and the beamforming technique. While each technique provided nearly the same direction as a most likely estimate, the beamforming estimate was associated with the smallest uncertainties. Backazimuth anomalies were then calculated for the entire data set by comparing the results from beamforming with backazimuths derived from earthquake locations reported by the Anza and Caltech seismic networks and the Preliminary Determination of Epicenters (PDE) Bulletin. These backazimuth anomalies have a simple sinelike dependence on azimuth, with the largest anomalies observed from the southeast and northwest directions. Such a trend may be explained as the effect of one or more interfaces dipping to the northeast beneath the array. A best-fit model of a single interface has a dip and strike of 20° and 315°, respectively, and a velocity contrast of 0.82 km/sec. Application of corrections computed from this simple model to ray directions significantly improves locations at all distances and directions, suggesting that this is an upper crustal feature. We confirm that knowledge of local structure can be very important for earthquake location by an array but also show that corrections computed from simple models may not only be adequate but superior to those determined by raytracing through smoothed laterally varying models.

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