scholarly journals Near-field seismic displacement and tilt associated with the explosive activity of Stromboli

1999 ◽  
Vol 42 (3) ◽  
Author(s):  
E. Wielandt ◽  
T. Forbriger
Keyword(s):  
Near Field ◽  
Vertical Component ◽  
Local Strain ◽  
Vertical Displacement ◽  
Seismic Displacement ◽  
Time Integral ◽  
S Period ◽  
Summit Region ◽  
Strombolian Explosions ◽  
Tilt Signal

Broadband seismic recordings in the near-field of Strombolian explosions, at 500 m distance, show pronounced effects of tilt. The tilt signal is predominant in the horizontal components beyond about 50 s period while it is negligible in the vertical component. The waveform of the tilt signal at the seismometer output is a double time integral of the waveform due to ground displacement. Since the waveform of the displacement is known from the vertical component, the waveform of the tilt signal in the horizontal seismogram can be reconstructed and both contributions can be separated from each other with a linear regression. We have analyzed data recorded in the summit region of Stromboli in 1995 and 1996. The regional tilt can be determined from the differential vertical displacement between instruments a few tens of meters apart. Local tilts determined with individual instruments scatter around the regional value, most probably due to local strain-tilt-coupling. Mogi's (1958) formulae for a pressure source in a homogeneous halfspace are used to interpret the results. The source displaces a volume of several tens of cubic meters of the surrounding rock before the explosive discharge; typical volumes were 25 m3 in July 1995 and 60 m3 in September 1996.

scholarly journals Analysis and quasistatic FE modeling of long period impulsive events associated with explosions at Stromboli volcano (Italy)

1999 ◽  
Vol 42 (3) ◽  
Author(s):  
M. Kirchdörfer
Keyword(s):  
Near Field ◽  
Solid Cone ◽  
Long Period ◽  
Short Period ◽  
Wave Forms ◽  
Hydrostatic Model ◽  
Summit Region ◽  
Strombolian Explosions ◽  
Period Wave ◽  
Seismic Measurements

Broadband seismic measurements performed in 1995 and 1996 in the summit region of Stromboli are analyzed. The experiment in 1995 used an array of four Guralp seismometers and one Wielandt-Streckeisen seismometer. The stations were installed around the craters in a semicircle with a radius of about 500 m. This implies that the seismic signals are dominated by near field motions up to frequencies of about 2 Hz. The observed Strombolian explosions are preceded by long-period ground motions occurring between 20 s and 70 s prior to the ejections. They are obviously generated by a slow pressure increase within the magma conduits. The long-period signals are simple compared to the short period wave forms. Four classes of pulse-shaped seismograms can be distinguished. The radiation pattern is radially symmetric with respect to the crater region. Particle motion analysis indicates that the seismic sources are located between 50 and 200 m below the crater terrace. Hydrostatic model sources were studied by means of finite element calculations with different geometries, i.e. ellipsoids, in a solid cone modeling the topography of Stromboli. The results suggest that the explosive events on Stromboli originate from a shallow vertically elongated volume source.

Multifault complex rupture and afterslip associated with the 2018 Mw 6.4 Hualien earthquake in northeastern Taiwan

2020 ◽  
Vol 224 (1) ◽  
pp. 416-434
Author(s):  
Dezheng Zhao ◽  
Chunyan Qu ◽  
Xinjian Shan ◽  
Roland Bürgmann ◽  
Wenyu Gong ◽  
...  
Keyword(s):  
Main Shock ◽  
Near Field ◽  
Active Faults ◽  
Fault Model ◽  
Body Waves ◽  
Coseismic Deformation ◽  
Coseismic Slip ◽  
Coulomb Stress Changes ◽  
Seismic Displacement ◽  
Stress Changes

SUMMARY We investigate the coseismic and post-seismic deformation due to the 6 February 2018 Mw 6.4 Hualien earthquake to gain improved insights into the fault geometries and complex regional tectonics in this structural transition zone. We generate coseismic deformation fields using ascending and descending Sentinel-1A/B InSAR data and GPS data. Analysis of the aftershocks and InSAR measurements reveal complex multifault rupture during this event. We compare two fault model joint inversions of SAR, GPS and teleseismic body waves data to illuminate the involved seismogenic faults, coseismic slip distributions and rupture processes. Our preferred fault model suggests that both well-known active faults, the dominantly left-lateral Milun and Lingding faults, and previously unrecognized oblique-reverse west-dipping and north-dipping detachment faults, ruptured during this event. The maximum slip of ∼1.6 m occurred on the Milun fault at a depth of ∼2–5 km. We compute post-seismic displacement time series using the persistent scatterer method. The post-seismic range-change fields reveal large surface displacements mainly in the near-field of the Milun fault. Kinematic inversions constrained by cumulative InSAR displacements along two tracks indicate that the afterslip occurred on the Milun and Lingding faults and the west-dipping fault just to the east. The maximum cumulative afterslip of 0.4–0.6 m occurred along the Milun fault within ∼7 months of the main shock. The main shock-induced static Coulomb stress changes may have played an important role in driving the afterslip adjacent to coseismic high-slip zones on the Milun, Lingding and west-dipping faults.

scholarly journals Seismic Vertical Component Effects on the Pathology of a Historical Structure, Xana, Located in Greece

2021 ◽  
Vol 7 ◽  
Author(s):  
Vasiliki Terzi ◽  
Asimina Athanatopoulou
Keyword(s):  
Seismic Analysis ◽  
Near Field ◽  
Three Dimensional ◽  
Vertical Component ◽  
Element Model ◽  
Material Behavior ◽  
Initial State ◽  
Tensile Cracks ◽  
First Case ◽  
Three Dimensional Finite Element

The present study aims to investigate the effects of the seismic vertical component on the pathology of Xana monument which is a typical caravanserai, constructed circa 1375–1385 and is located in the archeological site of the municipality of Trainapoulis, Greece. The monument’s plan is rectangular and the three-leaf masonry circumferential walls support a hemicylindrical dome constructed by bricks and mortar. The structure consisted of two consecutive parts: one for the travelers and one for the animals. Nowadays, the triangular roof, that covered the structure, and the first part of the monument do not exist. Xana suffers tensile cracks along the interior surface of the dome, a vertical fracture located on the northern wall and vertical tensile cracks located at the openings. A three-dimensional finite element model of the initial state of Xana is constructed. Non-linear material behavior is taken into account as well as soil-structure interaction effects. An adequate number of near-field earthquake events has been used, taking into account that they are related to significant vertical components. The structural seismic analysis is conducted for two cases. The first case refers to the action of the two horizontal-component of ground motions while the second one takes into account the three translational seismic components. The pathology estimation reveals important information concerning the structural effects due to vertical accelerations.

Magnetic Field Variations in Alaska: Recording Space Weather Events on Seismic Stations in Alaska

2020 ◽  
Vol 110 (5) ◽  
pp. 2530-2540 ◽  
Author(s):  
Adam T. Ringler ◽  
Robert E. Anthony ◽  
David C. Wilson ◽  
Abram C. Claycomb ◽  
John Spritzer
Keyword(s):  
Magnetic Field ◽  
Ground Motion ◽  
Space Weather ◽  
Vertical Component ◽  
Environmental Data ◽  
Magnetic Data ◽  
Seismic Stations ◽  
Weather Events ◽  
S Period ◽  
Magnetic Field Variations

ABSTRACT Seismometers are highly sensitive instruments to not only ground motion but also many other nonseismic noise sources (e.g., temperature, pressure, and magnetic field variations). We show that the Alaska component of the Transportable Array is particularly susceptible to recording magnetic storms and other space weather events because the sensors used in this network are unshielded and magnetic flux variations are stronger at higher latitudes. We also show that vertical-component seismic records across Alaska are directly recording magnetic field variations between 40 and 800 s period as opposed to actual ground motion during geomagnetic events with sensitivities ranging from 0.004 to 0.48  (m/s2)/T. These sensitivities were found on a day where the root mean square variation in the magnetic field was 225 nT. Using a method developed by Forbriger (2007, his section 3.1), we show that improving vertical seismic resolution of an unshielded sensor by as much as 10 dB in the 100–400 s period band using magnetic data from a collocated three-component magnetometer is possible. However, due to large spatial variations in Earth’s magnetic field, this methodology becomes increasingly ineffective as the distance between the seismometer and magnetometer increases (no more than 200 km separation). A potential solution to this issue may be to incorporate relatively low-cost magnetometers as an additional environmental data stream at high-latitude seismic stations. We demonstrate that the Bartington Mag-690 sensors currently deployed at Global Seismographic Network sites are not only acceptable for performing corrections to seismic data, but are also capable of recording many magnetic field signals with similar signal-to-noise ratios, in the 20–1000 s period band, as the observatory grade magnetometers operated by the U.S. Geological Survey Geomagnetism Program. This approach would densify magnetic field observations and could also contribute to space weather monitoring by supplementing highly calibrated magnetometers with additional sensors.

scholarly journals Post-seismic deformation mechanism of the July 2015 MW 6.5 Pishan earthquake revealed by Sentinel-1A InSAR observation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Sijia Wang ◽  
Yongzhi Zhang ◽  
Yipeng Wang ◽  
Jiashuang Jiao ◽  
Zongtong Ji ◽  
...  
Keyword(s):  
Near Field ◽  
Descent Method ◽  
Aftershock Sequence ◽  
Steepest Descent Method ◽  
Creep Process ◽  
Driving Mechanism ◽  
The Tibetan Plateau ◽  
Seismic Displacement ◽  
Sbas Insar ◽  
Seismic Deformation

Abstract On 3 July 2015, the Mw 6.5 Pishan earthquake occurred at the junction of the southwestern margin of the Tarim Basin and the northwestern margin of the Tibetan Plateau. To understand the seismogenic mechanism and the post-seismic deformation behavior, we investigated the characteristics of the post-seismic deformation fields in the seismic area, using 9 Sentinel-1A TOPS synthetic aperture radar (SAR) images acquired from 18 July 2015 to 22 September 2016 with the Small Baseline Subset Interferometric SAR (SBAS-InSAR) technique. Postseismic LOS deformation displayed logarithmic behavior, and the temporal evolution of the post-seismic deformation is consistent with the aftershock sequence. The main driving mechanism of near-field post-seismic displacement was most likely to be afterslip on the fault and the entire creep process consists of three creeping stages. Afterward, we used the steepest descent method to invert the afterslip evolution process and analyzed the relationship between post-seismic afterslip and co-seismic slip. The results witness that 447 days after the mainshock (22 September 2016), the afterslip was concentrated within one principal slip center. It was located 5–25 km along the fault strike, 0–10 km along with the fault dip, with a cumulative peak slip of 0.18 m. The 447 days afterslip seismic moment was approximately 2.65 × 1017 N m, accounting for approximately 4.1% of the co-seismic geodetic moment. The deep afterslip revealed that a creeping process from steady-state “secondary” creeping to accelerating “tertiary” creep in the deep of fault. The future seismic hazard deserves further attention and research.

scholarly journals Probing dark exciton navigation through a local strain landscape in a WSe2 monolayer

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Ryan J. Gelly ◽  
Dylan Renaud ◽  
Xing Liao ◽  
Benjamin Pingault ◽  
Stefan Bogdanovic ◽  
...  
Keyword(s):  
High Strain ◽  
Single Photon ◽  
Near Field ◽  
Local Strain ◽  
Cryogenic Temperatures ◽  
Photon Sources ◽  
Tapered Optical Fiber ◽  
Long Lifetime ◽  
And Diffusion ◽  
Dark Exciton

AbstractIn WSe2 monolayers, strain has been used to control the energy of excitons, induce funneling, and realize single-photon sources. Here, we developed a technique for probing the dynamics of free excitons in nanoscale strain landscapes in such monolayers. A nanosculpted tapered optical fiber is used to simultaneously generate strain and probe the near-field optical response of WSe2 monolayers at 5 K. When the monolayer is pushed by the fiber, its lowest energy states shift by as much as 390 meV (>20% of the bandgap of a WSe2 monolayer). Polarization and lifetime measurements of these red-shifting peaks indicate they originate from dark excitons. We conclude free dark excitons are funneled to high-strain regions during their long lifetime and are the principal participants in drift and diffusion at cryogenic temperatures. This insight supports proposals on the origin of single-photon sources in WSe2 and demonstrates a route towards exciton traps for exciton condensation.

Quantitative Scanned Probe Microscopy

1996 ◽  
Vol 54 ◽  
pp. 874-875
Author(s):  
J.C. Russ ◽  
P. J. Scott
Keyword(s):  
Near Field ◽  
Tunneling Current ◽  
Dimensional Accuracy ◽  
Scanning Speed ◽  
Limited Range ◽  
Internal Resistance ◽  
Atomic Scale ◽  
Time Integral ◽  
Limited Range Of Motion ◽  
Tip Position

The great advantage of the atomic force microscope and related technologies (tunneling current, near field optical, tips that oscillate vertically or laterally, etc.) has been simplicity of design. Vertical deflection of a reference tip on a cantilevered probe is detected by light scattering and used to shift the sample in the z direction to restore tip position. The output is generally in the form of surface images rather than measurements with high dimensional accuracy. Atomic scale resolution is achievable but lower magnification imaging is more difficult.Piezo devices used for x-y and z axis control have a limited range of motion and are noisy, nonlinear and subject to creep. Piezo displacement is not simply a function of voltage, or of the time integral of current, but depends upon many factors including rate and distance of motion, and internal resistance and capacitance in the device. It is possible in principle to calibrate such a system using a reference grid standard, but even this is highly dependent on scanning speed (different in the x, y, z directions) and will not provide quantitative z information.

scholarly journals Fragility Analysis of Gantry Crane Subjected to Near-Field Ground Motions

2020 ◽  
Vol 10 (12) ◽  
pp. 4219
Author(s):  
Qihui Peng ◽  
Wenming Cheng ◽  
Hongyu Jia ◽  
Peng Guo
Keyword(s):  
Failure Probability ◽  
Structural Damage ◽  
Fragility Curves ◽  
Damage Control ◽  
Ground Motions ◽  
Near Field ◽  
Vertical Component ◽  
Gantry Crane ◽  
Fe Model ◽  
Demand Model

A gantry crane located in a near-field earthquake-prone area is selected in this paper as an example, and the nonlinear finite element (FE) model is used considering the material nonlinearity including plastic hinges and the second order (P − Δ ) effect with a comprehensive consideration of the components including sill beams, support beams, legs, and trolley girders. The local displacement ratio (LDR) and deflection ratio (DR) are proposed as demand measures (DMs) of the gantry crane, which are utilized to construct a probabilistic seismic demand model (PSDM). Then, the capacity limit states for the gantry crane are defined in this study by performing pushover analysis (POA), known as serviceability, damage control, and collapse prevention, respectively. Moreover, the operating capacity of the crane during an earthquake is further investigated and quantified by operating seismic peak ground acceleration, which is defined as the maximum acceleration when the failure probability is 50%. Finally, the fragility curves and the failure probability of the gantry crane are derived by the above definitions, all of which are pioneering in the seismic design of gantry cranes subjected to near-field ground motions. Some major conclusions are drawn that the horizontal component of an earthquake has a more notable effect on the structural damage of the gantry crane compared to the vertical component, and incremental dynamic analysis can take seismic uncertainty into account and quantify the deformation of gantry crane in more detail.

Seismic radiation from an explosive column

Geophysics ◽  
2010 ◽  
Vol 75 (1) ◽  
pp. E55-E65 ◽  
Author(s):  
Dane Blair
Keyword(s):  
Rise Time ◽  
Numerical Models ◽  
Near Field ◽  
Blast Hole ◽  
Mining Industry ◽  
Field Measurements ◽  
Analytic Model ◽  
Seismic Displacement ◽  
Hole Radius ◽  
Velocity Of Detonation

A scale-independent analytic model of seismic radiation from a column of explosive is derived in terms of the blast hole radius [Formula: see text], charge length, explosive velocity of detonation (VoD), and distance [Formula: see text] to a monitoring station. The treatment is based on linear viscoelasticity in which the nonlinear response of rock close to the blast hole is modeled as a sufficiently low-[Formula: see text] material having an exponential increase in [Formula: see text] with distance from the source. Although limited by this assumption, the present analytic model avoids the more serious discretization problems associated with numerical models when driven by the high-frequency pressure load. Furthermore, numerical models are not useful in displaying scale independence. Exploration and mining geophysics typically require short explosive charges characterized by a length/radius of approximately 10. The model shows that for such charges ata small [Formula: see text], the seismic displacement increases with the VoD; however, as the [Formula: see text] increases, the displacement becomes insensitive to the VoD. Field measurements of seismic-wave transmission resulting from short charges show that a plot of rise time against traveltime is approximately linear, with an intercept that traditionally is assumed to be the rise time of the explosive source itself. However, the present model shows that this assumption is incorrect and suggests that if measurements could be made very close to the blast hole, then the rise-time plot would be nonlinear and well might correspond to the region of nonlinear rock response. The extractive mining industry typically requires long explosive columns characterized by a length/radius [Formula: see text], for which [Formula: see text] typifies the near-field. The model predicts that seismic transmission in this region is dominated completely by P-Mach and S-Mach wave propagation, dependent on the VoD.

Internal co-seismic displacement and strain changes inside a homogeneous spherical Earth

2021 ◽  
Author(s):  
Jie Dong ◽  
Pengfei Cheng ◽  
Hanjiang Wen ◽  
Wenke Sun
Keyword(s):  
Epicentral Distance ◽  
Near Field ◽  
Strike Slip ◽  
Point Sources ◽  
Earth Model ◽  
Curvature Effect ◽  
Seismic Displacement ◽  
Analytical Foundation ◽  
Deformation Properties ◽  
Spherical Earth

Summary In this study, we devised a new set of analytical foundation solutions to compute the internal co-seismic displacement and strain changes caused by four independent point sources (strike-slip, dip-slip, horizontal tensile, and vertical tensile) inside a homogeneous spherical Earth model. Our model provides constraints on the deformation properties at depth, and reveals that the internal co-seismic deformation is larger than that on the surface. The deformation near the source is convergent with our formulae. For the internal deformation at radial section plane, the patterns of horizontal displacements ${u_\theta },{u_\phi }$ and strain changes ${e_{rr}},{e_{\theta \theta }},{e_{\phi \phi }},{e_{\theta \phi }}$ caused by strike-slip and tensile sources appear symmetric at the equidistance above and below the source. Their amplitudes are not identical but with a small discrepancy actually. Unlike these, the patterns of radial displacements ${u_r}$ for strike-slip and tensile sources exhibit point symmetry with the equidistance from the source. Also, the corresponding amplitudes are slightly different. The displacements ${u_\theta },{u_\phi }$ and strain changes ${e_{rr}},{e_{\theta \theta }},{e_{\phi \phi }},{e_{\theta \phi }}$ caused by dip-slip also appear the same properties as ${u_r}$ of strike-slip source. The magnitudes of the displacements and strain changes depend on the source types. The curvature effect on the near-field surface deformations is small, and it increases with the studied depth. But for the far-field deformation caused by the strike-slip source (ds = 20 km), the curvature effect can be as large as 77 per cent when the epicentral distance approximates to 1778 km.

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