scholarly journals On the origin of the long-period tremor recorded at Stromboli volcano (Italy)

1996 ◽  
Vol 39 (2) ◽  
Author(s):  
T. Braun ◽  
J. Neuberg ◽  
M. Ripepe
Keyword(s):  
Particle Motion ◽  
Plane Waves ◽  
Seismic Source ◽  
Stromboli Volcano ◽  
Volcanic Origin ◽  
Arrival Times ◽  
Long Period ◽  
Volcanic Source ◽  
Seismic Amplitudes ◽  
Primary Frequency

This investigation deals with the nature of the long-period seismic signals (>1 s) observed at Stromboli and addresses the question whether they are of volcanic origin or produced by sources such as Ocean Microseisms (OMS). We present results from the analysis of seismic broadband data recorded during 1992 by an array of 9 Guralp CMG-3T seismometers. The determination of the Array Response Function (ARF) shows that array techniques like delay-and-sum beamforming cannot be applied for this purpose, as the extension of the array is limited by the geographical constraint of the island of Stromboli volcano, being simply too small. Spectral analysis reveals three main peaks with periods at 4.8 s, 6 s and 10 s which are not stable in time but vary according to the regional meteorological situation. Whereas 4.8 s and 10 s show up in amplitude spectra calculated during rainy and stormy weather, the 6 s period can be observed during a period of good weather. The signals were first narrowly filtered and then cross correlation, particle motion and amplitudes of the main long periods studied in detail. Relative arrival times as well as seismic amplitudes of the filtered traces do not show any systematic feature but vary with time. Particle motion analysis demonstrates that all long-period signals are recorded by the array as plane waves and that the main propagation direction of the 10 s signal is parallel to the wind direction. No correlation with volcanic activity is obvious. We conclude therefore that the three main long periods are not generated by a close volcanic source. We assume a local cyclone to be the seismic source at 4.8 s and 10 s, which represent the Double Frequency (DF-band) and the Primary Frequency (PF-band), respectively. Concerning the 6 s peak, we speculate a cyclone near the British Isles to act as a seismic source.

An automated Rayleigh-wave detection algorithm

1997 ◽  
Vol 87 (1) ◽  
pp. 157-163
Author(s):  
Eric P. Chael
Keyword(s):  
Rayleigh Wave ◽  
High Reliability ◽  
Detection Algorithm ◽  
Arrival Times ◽  
Long Period ◽  
Wave Detection ◽  
Linearly Polarized ◽  
Automated Data Processing ◽  
Component Wave ◽  
Elliptically Polarized

Abstract The desire to operate denser networks in order to monitor seismic activity at lower thresholds leads to greater emphasis on automated data processing. An algorithm for detecting and characterizing long-period Rayleigh-wave arrivals has been developed and tested. The routine continuously monitors all directions of approach to a station, in a manner similar to beamforming. The detector is based on cross-powers between the Hilbert-transformed vertical and rotated horizontal signals, so it is sensitive to both the power and polarization properties of the three-component wave field. Elliptically polarized Rayleigh arrivals are enhanced, while linearly polarized Love waves and body phases are suppressed. A test using one month of data from station ANMO demonstrated that this technique can, with high reliability, detect Rayleigh arrivals that are visible on the records. The measured arrival times and azimuths are accurate enough to permit automated association of the detections to events in a bulletin.

scholarly journals Seismo-volcanic sources on Stromboli volcano

1996 ◽  
Vol 39 (2) ◽  
Author(s):  
J. Neuberg ◽  
R. Luckett
Keyword(s):  
Detailed Analysis ◽  
Particle Motion ◽  
Volcanic Edifice ◽  
Stromboli Volcano ◽  
Eruptive Activity ◽  
Strombolian Activity ◽  
Video Recordings ◽  
Surface Correction ◽  
Steep Slopes ◽  
Precise Time

A detailed analysis of broadband seismic recordings leads to models of eruption mechanisms for Strombolian activity. The data used comprise signals from arrays of nine three-component seismometers and video recordings of visual eruptive activity with precise time reference. As a major tool particle motion analysis is used to locate the seismo-volcanic sources. Here, a surface correction is employed to account for the effects of the steep slopes of the volcanic edifice. After careful filtering of the data single seismic phases can be separated and linked to corresponding eruptive features.

scholarly journals Estimation of relative source locations from seismic amplitude: application to earthquakes and tremors at Meakandake volcano, eastern Hokkaido, Japan

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Masashi Ogiso ◽  
Kiyoshi Yomogida
Keyword(s):  
Amplitude Ratio ◽  
Linear Equations ◽  
Site Amplification ◽  
New Method ◽  
Seismic Events ◽  
Arrival Times ◽  
Event Location ◽  
Tectonic Earthquakes ◽  
The Difference ◽  
Seismic Amplitudes

AbstractAlthough seismic amplitudes can be used to estimate event locations for volcanic tremors and other seismic events with unclear phase arrival times, the precision of such estimates is strongly affected by site amplification factors. Therefore, reduction of the influence of site amplification will allow more precise estimation of event locations by this method. Here, we propose a new method to estimate relative event locations using seismic amplitudes. We use the amplitude ratio between two seismic events at a given station to cancel out the effect of the site amplification factor at that station. By assuming that the difference between the hypocentral distances of these events is much smaller than their hypocentral distances themselves, we derive a system of linear equations for the differences in relative event locations. This formulation is similar to that of a master event location method that uses differences in phase arrival times. We applied our new method to earthquakes and tremors at Meakandake volcano, eastern Hokkaido, Japan. Comparison of the hypocentral distributions of volcano-tectonic earthquakes obtained thereby with those obtained from phase arrival times confirmed the validity of our new method. Moreover, our method clearly identified source migration among three source regions in the tremor on 16 November 2008, consistent with previous interpretations of other geophysical observations in our study area. Our method will thus be useful for detailed analyses of seismic events whose onset times are ambiguous.

scholarly journals Teleseismic source parameters and rupture characteristics of the 24 November 1987, Superstition Hills earthquake

1990 ◽  
Vol 80 (1) ◽  
pp. 43-56 ◽  
Author(s):  
Lorraine J. Hwang ◽  
Harold Magistrale ◽  
Hiroo Kanamori
Keyword(s):  
Source Parameters ◽  
Seismic Source ◽  
Point Sources ◽  
Body Waves ◽  
Rupture Velocity ◽  
Total Moment ◽  
Long Period ◽  
The North ◽  
The Difference ◽  
Northern Segment

Abstract Long-period body waves from the 24 November 1987, Superstition Hills earthquake are studied to determine the focal mechanism and spatial extent of the seismic source. The earthquake is a complex event consisting of two spatially distinct subevents with different focal mechanisms. Two consistent models of rupture are developed. For both models, the second subevent begins 8 sec after the initiation of the first subevent and the preferred centroid depth lies between 4 to 8 km. Model 1 consists of two point sources separated by 15 to 20 km along strike of the Superstition Hills fault. Model 2 consists of one point source and one line source with a rupture velocity of 2.5 km/sec with moment release distributed along strike of the focal plane at a distance of 10 to 22 km from the epicenter. These moment release patterns show that a significant amount of long-period energy is radiated from the southern segment of the fault. Total moment release for both models is approximately 8 × 1025 dyne-cm. Both models also suggest a change of dip from near vertical near the epicenter to steeply southwesterly dipping along the southern segment of the fault. The difference in rupture characteristics and fault dips seen teleseismically is also reflected in aftershock and afterslip data, and crustal structure underlying the two fault segments. The northern segment had more aftershocks and a smaller proportion of afterslip than the southern segment. The boundary between the two segments lies at a step in the basement that separates a deeper metasedimentary basement to the south from a shallower crystalline basement to the north.

scholarly journals Suprasubduction volcanism of Chukotka terrane in the late jurassic– early cretaceous (Arctic region, Russia)

2019 ◽  
pp. 78-91
Author(s):  
E. V. Vatrushkina ◽  
M. I. Tuchkova ◽  
S. D. Sokolov
Keyword(s):  
Significant Proportion ◽  
Arctic Region ◽  
Geochemical Analysis ◽  
Pyroclastic Material ◽  
Volcanic Origin ◽  
Volcanic Source ◽  
The Matrix ◽  
Back Arc ◽  
Isotope Dating ◽  
Cretaceous Deposits

Abstract The age and geodynamic position of the volcanic source of the Upper JurassicLower Cretaceous deposits of Western Chukotka were determined. Products of synchronous volcanism were revealed by detailed lithological studies. Following sedimentological analysis results we established an admixture of pyroclastic material in the Oxford-Kimmeridgian deposits of the Chukotka microcontinent, indicating the effect of synchronous volcanism on sedimentation. It was shown that the source of pyroclastic material was the intraoceanic Kulpolney island arc, which existed in the northern part of the Proto-Arctic Ocean.The accumulation of the Tithonian‒ Valanginian deposits occurred in the back-arc basin at the edge of Chukotka microcontinent. Characteristics of the Tithonian‒ Berriasian sandstones are given, which contain significant proportion of ash material in the matrix, as well as lithoclasts and monomineral grains of volcanic origin, predominant in the clasts. With the use of geochemical analysis of volcanic pebbles, the presence of the differentiated series from basaltic andesites to rhyolites in the volcanic source is proved. The suprasubduction origin of the volcanic source is established. The cessation of volcanic activity in Valangin era is confirmed by lack of presence of synchronous pyroclastic material and an insignificant amount of volcanic clasts in Valanginian sandstones. The obtained data of UPb isotope dating of zircons isolated from the Tithonian-Valanginian sandstones and andesite pebbles of the Tithonian conglomerates made it possible to determine the time for the existence of suprasubduction volcanism on the Chukotka margin in the period of 150140 Ma.

Seismo-acoustic characterization of the 2019 Stromboli volcano paroxysm events

2021 ◽  
Author(s):  
Alexis Le Pichon ◽  
Emanuele Marchetti ◽  
Christoph Pilger ◽  
Lars Ceranna ◽  
Viviane Souty ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Civil Aviation ◽  
Stromboli Volcano ◽  
Efficient Tool ◽  
Propagation Modeling ◽  
Volcanic Source ◽  
Acoustic Characterization ◽  
Eruptive Column ◽  
International Monitoring

<p>Stromboli volcano is well known for its persistent explosive activity, with hundreds of explosions every day ejecting ash and scoria up to heights of several tens/few hundreds of meters. Such a mild activity is however punctuated by lava flows and major/paroxysmal explosions, that represent a much larger hazard. On July 3rd and August 28th 2019, two paroxysmal explosions occurred at Stromboli, generating an eruptive column that quickly raised up to 5 km above the sea level. The Toulouse Volcanic Ash Advisory Center (VAAC) emitted an advisory to the civil aviation with a two-hour delay. The various processes of this event were monitored near and far field by infrasonic arrays up to distance of 3,500 km and by the Italian national seismic network at range of hundreds of kilometres. Using state-of-the-art propagation modeling, we aim at identifying the various seismic and infrasound phases of the event to better characterize the volcanic source. We highlight the need for the integration of the global infrasound International Monitoring System (IMS) network with local and regional infrasound arrays capable of providing a timely early warning to VAACs. This study opens new perspectives in volcano monitoring for hazard assessment and could represent, in the future, an efficient tool in supporting VAACs activity.</p>

Free spheroidal vibrations of the earth at very long periods, Part II— effect of rigidity of the inner core

1963 ◽  
Vol 53 (3) ◽  
pp. 503-515
Author(s):  
Leonard E. Alsop
Keyword(s):  
Particle Motion ◽  
Inner Core ◽  
Shear Velocity ◽  
Free Vibrations ◽  
Numerical Calculations ◽  
Core Mode ◽  
Long Period ◽  
The Earth ◽  
Many Core ◽  
Core Modes

Abstract Numerical calculations have been made on an IBM 7090 of the periods and particle motion with depth of the lowest order free spheroidal vibrations of the fundamental and first two higher modes with inner core shear velocity as a parameter. All calculations were made for a model with velocities according to Jeffreys and with densities obeying Bullen's model B. These calculations show that the effect of the inner core shear velocity on these periods is slight, except for those velocities at which the modes have periods near to the periods of core modes. This means that observations of long period free vibrations will probably not give much information about rigidity of the inner core. A mode of vibration having many of the properties of the mode suggested by Slichter has been discovered. In addition, it appears that the presence of a solid inner core brings into existence many core type modes with periods both shorter and longer than the original core mode predicted by Alterman, Jarosch, and Pekeris.

Analytical Model for Tsunami Propagation including Source Kinematics

2020 ◽  
Author(s):  
Mauricio Fuentes ◽  
Francisco Uribe ◽  
Sebastian Riquelme ◽  
Jaime Campos
Keyword(s):  
Seismic Source ◽  
Rupture Velocity ◽  
Tsunami Propagation ◽  
Specific Domain ◽  
Static Approximation ◽  
Arrival Times ◽  
Slow Earthquakes ◽  
Set Up ◽  
Seismic Models ◽  
Time Description

<p>There are only a few analytical 2+1 D models for tsunami propagation, in which most of them treat the tsunami generation as an isolated part from a static deformation field, usually obtained from seismic models. This work examines the behavior of the tsunami propagation in a simple set-up including a time source function which accounts for a time description of the rupture process on the seismic source. An analytical solution is derived in the wavenumber domain, which is quickly inverted to space with the Fast Fourier Transform. The solution is obtained in closed form in the 1+1D case. The inclusion of temporal parameters of the source such as rise time and rupture velocity reveals a specific domain of slow earthquakes that enhance the tsunami amplitudes and produce non-negligible shifts on the arrival times. The obtained results confirm that amplification occurs when the rupture velocity matches the long-wave tsunami speed and the static approximation corresponds to a limit case for (relatively) fast ruptures. </p>

Calculation of seismic source mechanisms

1966 ◽  
Vol 290 (1422) ◽  
pp. 408-429 ◽  
Keyword(s):  
Equations Of State ◽  
Seismic Source ◽  
Computer Code ◽  
Stress Deviator ◽  
Two Dimensional ◽  
One Dimensional ◽  
Displacement Potential ◽  
Solid Region ◽  
Source Mechanisms ◽  
Seismic Amplitudes

A method has been developed which allows computation, in the inelastic region and near the inelastic-elastic boundary, of the Earth motions resulting from an underground nuclear detonation. It utilizes a one-dimensional digital computer code in which the conservation equations are transformed to difference equations in Lagrangian form. Changes of state from gas to liquid to solid are handled by switching to different equations of state as the internal energy drops below the enthalpy of vaporization and fusion, respectively. Within the solid region, inelastic processes such as plastic yielding, crushing, or cracking are handled by changing the stress deviator equations. Throughout the calculation, the time and space dependence of the shock wave parameters as well as the rate of energy deposition and material behaviour behind the shock front is tied to experimentally determined properties of materials including among others the Hugoniot equations of state. Experimental confirmation of this method is most convincing in the region above 10 kbar, where peak radial stresses measured on detonations in granite, dolomite, and salt agree, within 20 % , with predicted values, and those for detonations in tuff and alluvium agree within 30 % . Measured shock position curves from explosions in granite, tuff, and alluvium are in excellent agreement with calculations. In the lower stress region the calculation is more difficult and not quite as successful. However, we now have substantial agreement between calculated and experimental stress history data from detonations in granite, alluvium, tuff, dolomite, and salt. We also have computed the reduced displacement potential both from calculated and measured displacements at 300 m from the Salmon explosion and find agreement to within 25 % in peak values—about the same as the amount of disagreement that exists between different measurements. This result is encouraging since it opens the possibility of calculating seismic amplitudes from essentially first principles. A two-dimensional computer code with capabilities similar to the one-dimensional one mentioned above also has been devised and is about to become operational. When it does, it will be able to handle two-dimensional sources as well as surface wave propagation problems.

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