scholarly journals The CMT Solution of the 1994 October 4 Shikotan Island Earthquake (MJMA=8.1) Recorded by Broad-band Strong-motion Seismographs

1995 ◽  
Vol 48 (3) ◽  
pp. 353-364
Author(s):  
Ikuo CHO ◽  
Ichiro NAKANISHI ◽  
Kazutoshi IMANISHI ◽  
Tamao SATO
Keyword(s):  
Broad Band ◽  
Strong Motion ◽  
Shikotan Island

scholarly journals Analysis of strong-motion data of the 1990 Eastern Sicily earthquake

1995 ◽  
Vol 38 (2) ◽  
Author(s):  
M. Di Bona ◽  
M. Cocco ◽  
A. Rovelli ◽  
R. Berardi ◽  
E. Boschi
Keyword(s):  
Frequency Band ◽  
Stress Drop ◽  
Seismic Moment ◽  
Ground Motions ◽  
Broad Band ◽  
Strong Motion ◽  
Moment Magnitude ◽  
Corner Frequency ◽  
Local Magnitude ◽  
The Moment

The strong motion accelerograms recorded during the 1990 Eastern Sicily earthquake have been analyzed to investigate source and attenuation parameters. Peak ground motions (peak acceleration, velocity and displacement) overestimate the values predicted by the empirical scaling law proposed for other Italian earthquakes, suggesting that local site response and propagation path effects play an important role in interpreting the observed time histories. The local magnitude, computed from the strong motion accelerograms by synthesizing the Wood-Anderson response, is ML = 5.9, that is sensibly larger than the local magnitude estimated at regional distances from broad-band seismograms (ML = 5.4). The standard omega-square source spectral model seems to be inadequate to describe the observed spectra over the entire frequency band from 0.2 to 20 Hz. The seismic moment estimated from the strong motion accelerogram recorded at the closest rock site (Sortino) is Mo = 0.8 x 1024 dyne.cm, that is roughly 4.5 times lower than the value estimated at regional distances (Mo = 3.7 x 1024 dyne.cm) from broad-band seismograms. The corner frequency estimated from the accelera- tion spectra i.5 J; = 1.3 Hz, that is close to the inverse of the dUl.ation of displacement pulses at the two closest recording sites. This value of corner tì.equency and the two values of seismic moment yield a Brune stress drop larger than 500 bars. However, a corner frequency value off; = 0.6 Hz and the seismic moment resulting from regional data allows the acceleration spectra to be reproduced on the entire available frequency band yielding to a Brune stress drop of 210 bars. The ambiguity on the corner frequency value associated to this earthquake is due to the limited frequency bandwidth available on the strong motion recordil1gs. Assuming the seismic moment estimated at regional distances from broad-band data, the moment magnitude for this earthquake is 5.7. The higher local magnitude (5.9) compared with the moment magnitude (5.7) is due to the weak regional attenuation. Beside this, site amplifications due to surface geology have produced the highest peak ground motions among those observed at the strong motion sites.

scholarly journals A Laser-Based Optical Sensor for Broad-Band Measurements of Building Earthquake Drift

2017 ◽  
Vol 33 (4) ◽  
pp. 1573-1598 ◽  
Author(s):  
David McCallen ◽  
Floriana Petrone ◽  
Jason Coates ◽  
Nicholas Repanich
Keyword(s):  
Broad Band ◽  
Strong Motion ◽  
Structural Member ◽  
Time Dependent ◽  
Position Sensor ◽  
Computational Simulations ◽  
Earthquake Excitation ◽  
Seismic Demands ◽  
Building Systems ◽  
Traditional Approaches

Accurate measurements of the time-dependent deformations of a building during earthquake excitation are essential for interpretation of the dynamic response of the as-built system and for quantifying the seismic demands. Traditional approaches for monitoring building systems are based on strong motion accelerometers mounted at selected elevations. However, accelerometer-based systems do not directly measure the deformations of the structure, and can have significant limitations that make it challenging to correctly measure deformations, particularly permanent deformations from inelastic response. In the study described herein, computational simulations and experiments were combined to evaluate the potential of a new optically based sensor to directly measure time-dependent deformations of a building, including inelastic deformations. The sensor methodology includes corrections for localized structural member rotations and can provide estimates of the absolute accelerations at each floor. A laser-based system utilizing a recently developed discrete diode position sensor (DDPS) is evaluated, and the ability of such a system to measure earthquake induced transient deformations characterized by building interstory drift is demonstrated.

Aftershock Activity at Intermediate-Depth Earthquakes in Northern Chile Controlled by Plate Hydration

2020 ◽  
Author(s):  
Leoncio Cabrera ◽  
Sergio Ruiz ◽  
Piero Poli ◽  
Eduardo Contreras-Reyes ◽  
Renzo Mancini ◽  
...  
Keyword(s):  
Template Matching ◽  
Broad Band ◽  
Strong Motion ◽  
Seismic Source ◽  
Northern Chile ◽  
Aftershock Activity ◽  
Study Region ◽  
Abrupt Decrease ◽  
Intermediate Depth ◽  
The Impact

<p>We investigate the differences of the seismic source and aftershock activity using kinematic inversions and template matching respectively, for the six largest intraslab intermediate-depth earthquakes occurred in northern Chile (Mw ~6.3) since 2010 at depths between 90 and 130 km and recorded by dense strong-motion and broad-band seismic networks. In addition, we developed a thermal model using the finite element method in the study region with the aim of analyze the impact of temperature on seismic behavior as the oceanic plate subducts. Our results show that geometries of rupture zones are similar, with semi-axis for an elliptical patch approach about 5 km, and stress drop values between 7 and 30 MPa. On the other hand, the number of aftershocks exhibits clear differences, and their amount decreases with increasing the depth within the slab bounded by the 450 ºC isotherm, which represents a limit between a high-hydrated and a dry or low-hydrated region. Furthermore, mainshocks occur at distances from the top of the slab from 7 to 40 km, and all of them exhibit normal focal mechanisms suggesting that the extensional regimen deepens within the slab to the 700-750 ºC isotherm-depth. We suggest that in northern Chile the abrupt decrease of aftershocks in the lower part of the extensional regimen is caused by the absence of a hydrated slab at those depths.</p>

A very broad-band stochastic source model used for near source strong motion prediction

1998 ◽  
Vol 25 (7) ◽  
pp. 1063-1066 ◽  
Author(s):  
Catherine Berge ◽  
Jean-Christophe Gariel ◽  
Pascal Bernard
Keyword(s):  
Broad Band ◽  
Strong Motion ◽  
Source Model ◽  
Motion Prediction

scholarly journals Interplay of seismic and a-seismic deformation during the 2020 sequence of Atacama, Chile.

2021 ◽  
Author(s):  
Emilied Klein ◽  
Bertrand Potin ◽  
Francisco Pasten-Araya ◽  
Roxane Tissandier ◽  
Kellen Azua ◽  
...  
Keyword(s):  
Broad Band ◽  
Strong Motion ◽  
Velocity Model ◽  
High Rate ◽  
Aseismic Slip ◽  
Coseismic Slip ◽  
Narrow Strip ◽  
Rupture Area ◽  
3D Velocity Model ◽  
Largest Aftershock

An earthquake sequence occurred in the Atacama region of Chile throughout September 2020. The sequence initiated by a mainshock of magnitude Mw6.9, followed 17 hours later by a Mw6.4 aftershock. The sequence lasted several weeks, during which more than a thousand events larger than Ml 1 occurred, including several larger earthquakes of magnitudes between 5.5 and 6.4. Using a dense network that includes broad-band, strong motion and GPS sites, we study in details the seismic sources of the mainshock and its largest aftershock, the afterslip they generate and their aftershock, shedding light of the spatial temporal evolution of seismic and aseismic slip during the sequence. Dynamic inversions show that the two largest earthquakes are located on the subduction interface and have a stress drop and rupture times which are characteristics of subduction earthquakes. The mainshock and the aftershocks, localised in a 3D velocity model, occur in a narrow region of interseismic coupling (ranging 40%-80%), i.e. between two large highly coupled areas, North and South of the sequence, both ruptured by the great Mw~8.5 1922 megathrust earthquake. High rate GPS data (1 Hz) allow to determine instantaneous coseismic displacements and to infer coseismic slip models, not contaminated by early afterslip. We find that the total slip over 24 hours inferred from precise daily solutions is larger than the sum of the two instantaneous coseismic slip models. Differencing the two models indicates that rapid aseismic slip developed up-dip the mainshock rupture area and down-dip of the largest aftershock. During the 17 hours separating the two earthquakes, micro-seismicity migrated from the mainshock rupture area up-dip towards the epicenter of the Mw6.4 aftershocks and continued to propagate upwards at ~0.7 km/day. The bulk of the afterslip is located up-dip the mainshock and down-dip the largest aftershock, and is accompanied with the migration of seismicity, from the mainshock rupture to the aftershock area, suggesting that this aseismic slip triggered the Mw6.4 aftershock. Unusually large post-seismic slip, equivalent to Mw6.8 developed during three weeks to the North, in low coupling areas located both up-dip and downdip the narrow strip of higher coupling, and possibly connecting to the area of the deep Slow Sleep Event detected in the Copiapo area in 2014. The sequence highlights how seismic and aseismic slip interacted and witness short scale lateral variations of friction properties at the megathrust.

Real-time coseismic deformations from adaptively tight integration of high-rate GNSS and strong motion records

2019 ◽  
Vol 219 (3) ◽  
pp. 1757-1772 ◽  
Author(s):  
Jianfei Zang ◽  
Caijun Xu ◽  
Guanxu Chen ◽  
Qiang Wen ◽  
Shijie Fan
Keyword(s):  
Real Time ◽  
Central Italy ◽  
Broad Band ◽  
Strong Motion ◽  
High Rate ◽  
Motion Sensors ◽  
Observation Condition ◽  
Baseline Shift ◽  
Process Variance ◽  
Tight Integration

SUMMARY In traditional tight integration of high-rate GNSS and strong motion sensors, an appropriate process variance is crucial for obtaining accurate broad-band coseismic deformations. In this paper, instead of using a subjectively empirical value, we present an approach for determining the process variance adaptively based on the adaptive Kalman filter for real-time use. The performance of the approach was validated by the colocated stations collected during the 2010 Mw 7.2 earthquake in El-Mayor, 2016 Mw 7.8 earthquake in New Zealand and 2016 Mw 6.5 earthquake in central Italy. The results show that this method complements the advantages of GNSS and strong motion accelerometers and can provide more accurate coseismic waveforms especially during the strong shaking period, due to the ability of the method to adjust the process variance in real time according to the actual status of the station. In addition, this method is also free from the influence of the baseline shift. Testing of the new method for the integration of strong motion and multi-GNSS indicates that multi-GNSS has an obvious improvement in the precision while single GPS has a poor observation condition.

scholarly journals Microzone effects in the Hutt Valley in records from a strong-motion accelerograph array

1992 ◽  
Vol 25 (4) ◽  
pp. 246-264 ◽  
Author(s):  
S. Sritharan ◽  
G. H. McVerry
Keyword(s):  
Response Spectrum ◽  
Broad Band ◽  
Strong Motion ◽  
Soil Conditions ◽  
Ground Shaking ◽  
Amplification Curve ◽  
Response Characteristics ◽  
A Value ◽  
Short Period ◽  
S Period

Ground motions recorded in several earthquakes by the Hutt Valley strong-motion accelerograph array are analyzed to demonstrate and quantify microzone effects. Spectral amplifications in low to moderate ground shaking are calculated at sites with different soil conditions with respect to a reference site located on rock adjacent to the edge of the valley. It is shown that the response characteristics of various sites correlate well with the soil conditions underlying the sites. A shallow site located on 20 m of sediment adjacent to the edge of the valley produces short-period amplification, with the average amplification curve for the 5% damped acceleration response, spectrum peaking at 0.35 s with a value of 4. Deeper sites with up to 300 m of stiff sediments yield broad-band amplifications up to 2 s period, with typical maximum amplifications of 5-10. The greatest amplifications, exceeding 10, are obtained at two sites which are located on shallow very soft deposits.

The 2018 Mw 6.8 Zakynthos, Greece, earthquake – strike-slip and thrust faulting in shallow subduction

2020 ◽  
Author(s):  
Efthimios Sokos ◽  
František Gallovič ◽  
Christos P. Evangelidis ◽  
Anna Serpetsidaki ◽  
Vladimír Plicka ◽  
...  
Keyword(s):  
Numerical Models ◽  
Waveform Inversion ◽  
Broad Band ◽  
Strong Motion ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Plate Motion ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Fault Interaction

<p>On October 25, 2018, at 22:54 UTC, an Mw 6.8 earthquake occurred southwest of Zakynthos island in the Ionian Sea. This is an area with different styles of faulting and the locus of strong events thus ideal for fault interaction studies. The 2018 Zakynthos earthquake was recorded by broad-band and strong-motion networks and provides an opportunity to resolve such faulting complexity. We used waveform inversion and backprojection of strong motion data, partly verified by co-seismic GNSS data, too. The aftershock sequence was relocated, and the moment tensors of the strongest events were evaluated. Stress inversion shows that the region is under sub-horizontal southwest-northeast compression, enabling mixed thrust- and strike-slip faulting. Based on detailed waveform inversion studies, we conclude that the 2018 mainshock consisted of two fault segments: a low-dip thrust, and a dominant, moderate-dip, right-lateral strike slip, both in the crust. This model explains the observed large negative CLVD component of the mainshock. Slip vectors of both ruptured segments, oriented to SW, are consistent with plate motion in the area. The sequence can be explained in terms of trench-orthogonal fractures in the subducting plate and reactivated faults in the upper plate. The 2018 event, and an Mw 6.6 event of 1997, occurred near three localized swarms of 2016 and 2017. Future numerical models of the slab deformation and ocean-bottom seismometer observations may illuminate possible relations between earthquakes, swarms and fluid paths in the region.</p>

Sign in / Sign up

Export Citation Format

Share Document