Repetitive fracturing during spine extrusion at Unzen volcano, Japan

Abstract. Rhythmic seismicity associated with spine extrusion is a well-documented phenomenon at a number of dome-forming volcanic systems. At Unzen volcano, Japan, a 4-year dome-forming eruption concluded with the emplacement of a spine from October 1994 to February 1995, offering a valuable opportunity to further investigate seismogenic processes at dome-forming volcanoes. Using continuous data recorded at a seismic station located close to the dome, this study explores trends in the seismic activity during the extrusion of the spine. We identify a total of 12 208 volcano-seismic events in the period between October 1994 and February 1995. Hourly event counts indicate cyclic activity with periods of ∼ 40 to ∼ 100 h, attributed to pulsatory ascent defined by strain localisation and faulting at the conduit margins. Waveform correlation revealed two strong clusters (a.k.a. multiplets, families) which are attributed to fracturing along the margins of the shallow, ascending spine. Further analysis indicates variable seismic velocities during the spine extrusion as well as migration of the cluster sources along the spine margins. Our interpretation of the results from seismic data analyses is supported by previously published field and experimental observations, suggesting that the spine was extruded along an inclined conduit with brittle and ductile deformation occurring along the margins. We infer that changes in stress conditions acting on the upper and lower spine margins led to deepening and shallowing of the faulting sources, respectively. We demonstrate that the combination of geophysical, field and experimental evidence can help improve physical models of shallow conduit processes.

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Cyclic fracturing during spine extrusion at Unzen volcano, Japan

Solid Earth Discussions ◽

10.5194/sed-7-2109-2015 ◽

2015 ◽

Vol 7 (3) ◽

pp. 2109-2149 ◽

Cited By ~ 4

Author(s):

O. D. Lamb ◽

S. De Angelis ◽

K. Umakoshi ◽

A. J. Hornby ◽

J. E. Kendrick ◽

...

Keyword(s):

Seismic Data ◽

Seismic Station ◽

Ductile Failure ◽

Physical Models ◽

Seismic Events ◽

Seismic Velocities ◽

Strain Localisation ◽

Cyclic Activity ◽

Geophysical Field ◽

Unzen Volcano

Abstract. Rhythmic seismicity associated with spine extrusion is a well-documented phenomenon at a number of dome-forming volcanic systems. At Unzen volcano, Japan, a four year dome-forming eruption concluded with the emplacement of a spine from October 1994 to February 1995, offering a valuable opportunity to further investigate seismogenic processes at dome-forming volcanoes. Using continuous data recorded at a seismic station located close to the dome, this study explores trends in the seismic activity during the extrusion of the spine. We identify a total of 12 208 seismic events in the period between October 1994 and February 1995. Hourly event counts indicate cyclic activity with periods of ~ 40 to ~ 100 h, attributed to pulsatory ascent defined by strain localisation and faulting at the conduit margins. Waveform correlation revealed two strong clusters (a.k.a. multiplets, families) attributed to fracturing along the margins of the shallow, ascending plug. Further analysis indicates variable seismic velocities during spine extrusion, as well as migration of the cluster sources along the spine margins. Our interpretation of the results from seismic data analyses is supported by field and experimental observations, suggesting that the spine was extruded along an inclined conduit with brittle and ductile failure occurring along the margins. We infer that changes in stress conditions acting on the upper and lower spine margins led to deepening and shallowing of the faulting source, respectively. We demonstrate that the combination of geophysical, field and experimental evidence can help improve physical models of shallow conduit processes.

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Spectral ratio comparison between translation and rotational records from induced seismic events.

10.5194/egusphere-egu21-8817 ◽

2021 ◽

Author(s):

Dariusz Nawrocki ◽

Maciej Mendecki ◽

Lesław Teper

Keyword(s):

Seismic Data ◽

Seismic Station ◽

Spectral Ratio ◽

Numerical Differentiation ◽

Vertical Axis ◽

Frequency Range ◽

Signal Ratio ◽

Seismic Waveforms ◽

Seismic Tests ◽

Rotation Spectrum

The seismic observations of the rotational signals are a field of seismology that is constantly developed. The recent research concerns sensors technology and its potential application in seismic tests. This study presents the results of a comparative analysis of rotational and translational seismic records using the horizontal-to-vertical spectral ratio (HVSR) method. In terms of transitional signal ratio, we have used the name of HVSR, but in terms of rotational component spectra, we have introduced a torsion-to-rocking spectral ratio (TRSR) which corresponds to horizontal rotation spectrum to vertical rotation spectrum. It has to be noticed that rotation in the horizontal axes has a vertical character and rotation in the vertical axis has a horizontal character.The comparison was carried out between velocity signals of translational and rotational records, as well as, between acceleration signals respectively. All seismic data were recorded by two independent sensors: the rotational seismometer and translational accelerometer at the Imielin station, located in the Upper Silesia Coal Basin (USCB), Poland. The seismic data composed of three-component seismic waveforms related to 56 recorded tremors which were located up to 1,5 km from the seismic station and they resulted from the coal extractions carried out in the neighboring coal mines. The rotational acceleration was obtained by numerical differentiation and the translational velocity was produced by numerical integration.The conducted spectral analyses allowed to estimate the range of frequency in which the rotational HVSR and the corresponded translational HVSR are comparable. The analysis of HVSR/TRSR curves (in the selected frequency range of 1Hz to 10Hz) showed a strong correlation between the spectral ratios for the velocity signals (translational and rotational) in the frequency range of 1Hz to 2Hz. Respectively, the comparison of the accelerometer signals indicated the correlation between HVSR/TRSR curves in the frequency range of 1Hz to 3Hz. Moreover, both of the TRSR (for velocity and acceleration) showed additional maxima in the same frequency range of 3Hz to 5Hz. These relatively high-frequency maxima did not correspond to translational spectra. &#160;

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Musification of Seismic Data

Proceedings of the 22nd International Conference on Auditory Display - ICAD 2016 ◽

10.21785/icad2016.021 ◽

2016 ◽

Author(s):

Ryan McGee ◽

David Rogers

Keyword(s):

Wave Equation ◽

New Media ◽

Seismic Data ◽

Seismic Events ◽

Digital Audio ◽

The Public ◽

General Wave ◽

Musical Compositions ◽

The Creation ◽

Earth's Crust

Seismic events are physical vibrations induced in the earth’s crust which follow the general wave equation, making seismic data naturally conducive to audiﬁcation. Simply increasing the playback rates of seismic recordings and rescaling the amplitude values to match those of digital audio samples (straight audiﬁcation) can produce eerily realistic door slamming and explosion sounds. While others have produced a plethora of sucha udiﬁcations for international seismic events (i.e. earthquakes), the resulting sounds, while distinct to the trained auditory scientist, often lack enough variety to produce multiple instrumental timbres for the creation of engaging music for the public. This paper discusses approaches of soniﬁcation processing towards eventual musiﬁcation of seismic data, beginning with straight audiﬁcation and resulting in several musical compositions and new-media installations containing a variety of seismically derived timbres.

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Inferring significant wave height from seismic data: A comparison between methods.

10.5194/egusphere-egu21-14837 ◽

2021 ◽

Author(s):

Francisco Bolrão ◽

Co Tran ◽

Miguel Lima ◽

Sheroze Sheriffdeen ◽

Diogo Rodrigues ◽

...

Keyword(s):

Real Time ◽

Wave Height ◽

Seismic Data ◽

Significant Wave Height ◽

Transfer Functions ◽

Seismic Station ◽

Meteorological Data ◽

Ocean Waves ◽

The United States ◽

Significant Wave

The most pervasive seismic signal recorded on our planet &#8211; microseismic ambient noise -results from the coupling of energy between atmosphere, oceans and solid Earth. Because it carries information on ocean waves (source), the microseismic wavefield can be advantageously used to image ocean storms. This imaging is of interest both to climate studies &#8211; by extending the record of oceanic activity back into the early instrumental seismic record &#8211; and to real-time monitoring &#8211; where real-time seismic data can potentially be used to complement the spatially dense but temporally sparse satellite meteorological data. In our work, we develop empirical transfer functions between seismic observations and ocean activity observations, in particular, significant wave height. We employ three different approaches: 1) The approach of Ferretti et al (2013), who compute a seismic significant wave height and invert only for the empirical conversion parameters between oceanic and seismic significant wave heights; 2) The classical approach of Bromirski et al (1999), who computed an empirical transfer function between ground-motion recorded at a coastal seismic station and significant wave height measured at a nearby ocean buoy; and 3) A novel recurrent neural-network (RNN) approach to infer significant wave height from seismic data.&#160; We apply the three approaches to seismic and ocean buoy data recorded in the east coast of the United States. All three approaches are able to successfully predict ocean significant wave height from the seismic data. We compare the three approaches in terms of accuracy, computational effort and robustness. In addition, we investigate the regimes where each approach works best. &#160;The results show that the RNN approach is able to predict well the significant wave height recorded at the buoy. The prediction is improved if several nearby seismic stations are used rather than just one.&#160; This work is supported by FCT through projects UIDB/50019/2020 &#8211; IDL and UTAP-EXPL/EAC/0056/2017 - STORM.

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Predicting the azimuth of natural fractures and in-situ horizontal stress: A case study from Sichuan Basin, China

Geophysics ◽

10.1190/geo2020-0829.1 ◽

2021 ◽

pp. 1-97

Author(s):

kai lin ◽

Bo Zhang ◽

Jianjun Zhang ◽

Huijing Fang ◽

Kefeng Xi ◽

...

Keyword(s):

Hydraulic Fracturing ◽

Seismic Data ◽

Sichuan Basin ◽

Horizontal Stress ◽

Seismic Attributes ◽

Seismic Events ◽

Natural Fractures ◽

Microseismic Data ◽

Maximum Horizontal Stress

The azimuth of fractures and in-situ horizontal stress are important factors in planning horizontal wells and hydraulic fracturing for unconventional resources plays. The azimuth of natural fractures can be directly obtained by analyzing image logs. The azimuth of the maximum horizontal stress σH can be predicted by analyzing the induced fractures on image logs. The clustering of micro-seismic events can also be used to predict the azimuth of in-situ maximum horizontal stress. However, the azimuth of natural fractures and the in-situ maximum horizontal stress obtained from both image logs and micro-seismic events are limited to the wellbore locations. Wide azimuth seismic data provides an alternative way to predict the azimuth of natural fractures and maximum in-situ horizontal stress if the seismic attributes are properly calibrated with interpretations from well logs and microseismic data. To predict the azimuth of natural fractures and in-situ maximum horizontal stress, we focus our analysis on correlating the seismic attributes computed from pre-stack and post-stack seismic data with the interpreted azimuth obtained from image logs and microseismic data. The application indicates that the strike of the most positive principal curvature k1 can be used as an indicator for the azimuth of natural fractures within our study area. The azimuthal anisotropy of the dominant frequency component if offset vector title (OVT) seismic data can be used to predict the azimuth of maximum in-situ horizontal stress within our study area that is located the southern region of the Sichuan Basin, China. The predicted azimuths provide important information for the following well planning and hydraulic fracturing.

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A Consistent Thermo-Compositional Model of the South American Cratonic Lithosphere from Integrated Inversion of Gravity and Seismic Data

10.5194/egusphere-egu2020-22408 ◽

2020 ◽

Author(s):

Nils-Peter Finger ◽

Mikhail Kaban ◽

Magdala Tesauro ◽

Carina Haeger ◽

Walter Mooney ◽

...

Keyword(s):

South America ◽

Upper Mantle ◽

Seismic Data ◽

Seismic Velocities ◽

Double Positive ◽

Mineral Physics ◽

Compositional Model ◽

Positive Ions ◽

Gravity Signal ◽

Crustal Density

We present an integrated model of the cratonic lithosphere of South America. Gravity and seismic data were jointly analyzed using mineral physics constraints to assess state and evolution of the cratonic roots in South America in terms of temperature, density and composition. At the cratons, our model enables separation of two counteracting effects: the increased density due to cooling with age and decreased density due to depletion of iron. The depletion of iron can be described by the Mg# which gives the partition of Mg2+ among the double positive ions. A new crustal model (including depth to the Moho) based on existing seismic data was used to correct the gravity field for crustal effects and to uncover the gravity signal of the mantle. In addition, residual topography was calculated as a measure of the part of topography not balanced by the crustal density variations and depth to the Moho. Temperatures within the lithospheric mantle were estimated based on seismic velocities and mineral physics equations, initially assuming a juvenile mantle composition (Mg# of 89). The residual fields were corrected for the respective effects. In the following inversion of residual gravity and topography, we have determined additional density variations which can be interpreted as compositional ones. Furthermore, these results were employed to recompute the upper mantle temperatures taking into account possible compositional changes in the cratonic roots. In this iterative procedure, a consistent thermo-compositional model of the upper mantle has been obtained. Negative compositional density variations imply depletion of iron, leading to higher Mg#s. The highest depletion occurs in the Amazonas and S&#227;o Francisco Cratons reaching values in the cratons&#8217; centers of up to 90 (Mg#). At the same time, their centers show very low temperatures, down to 600&#176;&#160;C in the depth of 100&#160;km. They stay below 1300&#176;&#160;C even at a depth of 200&#160;km, indicating deep lithospheric roots. Higher temperatures are found in the Andean forelands and along the Trans-Brasiliano-Lineament (TBL), dividing the Amazonas and S&#227;o Francisco Cratons. Compositional density variations yield smaller to no amounts of depletion in the Amazonas Craton below a depth of 100&#160;km. The S&#227;o Francisco Craton still shows depletion in 200&#160;km depth (Mg# up to 89.5). Slightly negative compositional density variations southwest of the S&#227;o Francisco Craton also exist at depths up to 200&#160;km, indicating the Paranapanema cratonic fragment.

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Velocity‐depth ambiguity in the dipping reflector case

Geophysics ◽

10.1190/1.1444260 ◽

1997 ◽

Vol 62 (5) ◽

pp. 1583-1585 ◽

Cited By ~ 5

Author(s):

Brijpal S. Rathor

Keyword(s):

Acoustic Wave ◽

Wave Velocity ◽

Seismic Data ◽

Seismic Events ◽

Velocity Analysis ◽

Vital Parameter ◽

Acoustic Wave Velocity ◽

Analysis Methods

Seismic or acoustic wave velocity is a vital parameter for processing and interpretation of seismic data. Various velocity analysis methods, using traveltime moveout of seismic events, have been described in literature. In certain cases, these methods provide ambiguous results. Hence, there is a need to investigate velocity‐depth ambiguity in such cases.

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SEISMIC VELOCITIES IN THE SOUTHEASTERN SAN JOAQUIN VALLEY OF CALIFORNIA

Geophysics ◽

10.1190/1.1443730 ◽

1941 ◽

Vol 6 (4) ◽

pp. 327-355

Author(s):

E. J. Stulken

Keyword(s):

Seismic Data ◽

Seismic Velocity ◽

San Joaquin Valley ◽

Seismic Velocities ◽

Velocity Measurements ◽

Constant Depth ◽

Entire Area ◽

Velocity Gradients ◽

Velocity Changes ◽

First Time

For the first time, seismic velocity measurements from well surveys have been made intensively enough to justify an analysis of the velocity field in an entire area instead of just along lines between wells. Maps are drawn showing velocity changes in the southeastern San Joaquin Valley of California. A portion of the valley floor in the neighborhood of Bakersfield, about twenty‐five miles wide and thirty‐five miles long, was chosen for study because of the number of wells in the area whose velocities were known. Differences in average velocity of 1700 feet per second for a constant depth are observed, and horizontal velocity gradients averaging over 100 feet per second per mile are computed. Correction schemes for the adjustment of seismic data are suggested, and correction maps shown. An attempt is made to establish a connection between stratigraphy and seismic velocity. Comparative study of the logs of wells and the velocities observed in them yields certain qualitative conclusions, but attempts to express the relation in a quantitative way fail.

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On: “Approximating subsurface structure in areas of severe subsea erosion — A nonprocessing technique” by F. W. Lishman, and M. N. Christos (GEOPHYSICS, 54, 1397–1409, November 1989).

Geophysics ◽

10.1190/1.1442801 ◽

1990 ◽

Vol 55 (11) ◽

pp. 1512-1513

Author(s):

C. J. Blyth

Keyword(s):

Data Processing ◽

Seismic Data ◽

Seismic Velocities ◽

Subsurface Structure ◽

Reasonable Accuracy ◽

Processing Methods ◽

Sea Floor ◽

Accurate Model ◽

Mapping Structures ◽

Data Processing Methods

Two important questions were addressed in this paper. Firstly, how to construct an accurate model of a sea floor canyon — its topography and associated seismic velocities. Secondly, how the effects of such canyons can be accounted for in obtaining depths to subcanyon reflections using conventionally processed seismic data. An answer to the first question is required not only for deriving depths from conventional data but is equally required of the various canyon‐solving data processing methods listed in the paper (p. 1397). The second question is important, as the authors say, to provide a quick and inexpensive reconnaissance method of mapping structures in depth with reasonable accuracy.

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Seismic evidence for the migration of fluids within the accretionary complex of western Canada

Canadian Journal of Earth Sciences ◽

10.1139/e91-048 ◽

1991 ◽

Vol 28 (4) ◽

pp. 542-556 ◽

Cited By ~ 7

Author(s):

A. J. Calvert ◽

R. M. Clowes

Keyword(s):

Continental Slope ◽

Seismic Data ◽

Accretionary Prism ◽

Western Canada ◽

Accretionary Wedge ◽

Seismic Velocities ◽

Seismic Reflection Data ◽

Reflection Data ◽

Subducting Plate ◽

Important Evidence

Multichannel deep seismic reflection data from the subduction zone of western Canada delineate the wedge of accereted sediments and the principal terranes (Crescent, Pacific Rim, and Wrangellia) that form the convergent margin. The top of the igneous oceanic crust is defined by subhorizontal reflections extending at least 100 km landward of the deformation front. Upon incorporation into the accretionary wedge, the clearly defined stratigraphy of the incoming oceanic sedimentary section is destroyed over a distance of about 10 km. Initially, an unreflective zone, which correlates well with maximum fluid expulsion, is formed. Farther landward, a predominantly landward-dipping reflectivity exists. A number of reflections are thrust faults, which appear to merge at depth with the subhorizontal reflections, but most have another origin. These reflections may be related to the movement of fluids generated by the compaction of sediments or possibly by the dehydration of the subducting plate. They are strongest in a region of depressed seismic velocities beneath the continental slope, where an analysis of reflection amplitude with offset implies that a high Poisson's ratio exists; this is consistent with the presence of elevated pore pressures. Thus, pore pressure variations associated with the migration of fluids may be the cause of much of the reflectivity within the accreted wedge, although the precipitation of minerals from rising fluids could also be important. Evidence from the seismic data also indicates that fluids from the accretionary prism are being expelled into the sediments of the overlying Tofino basin. A number of anomalously strong reflections and disruption of the horizontally stratified sediments within the lower levels of the basin probably represent fluids that migrated upward from the accreted wedge and were trapped against impermeable barriers created through the deposition of sediments on the continental slope and in the basin.

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