Post-seismic crustal internal deformation in a layered earth model

2021 ◽  
Author(s):  
Tai Liu ◽  
Guangyu Fu ◽  
Yawen She ◽  
He Tang
Keyword(s):  
Northeast China ◽  
Near Field ◽  
Cumulative Effect ◽  
Seismic Source ◽  
Earth Model ◽  
Viscoelastic Relaxation ◽  
Layered Earth ◽  
Stress Changes ◽  
Internal Deformation ◽  
Seismic Deformation

Summary The present study introduces a novel method for computing post-seismic crustal internal deformation in a layered earth model. The surface dislocation Love number (DLN) calculated by the reciprocity theorem was implemented as the initial value. Furthermore, numerical integration of the value from the Earth's surface to the interior was undertaken to obtain the internal DLN. This method does not require a combination of the general solution and particular solution for the calculation of internal deformation above the seismic source, thus avoiding the loss of precision. When the post-seismic deformation within a certain period is calculated, the particular solutions at the beginning and end of the considered period cancel each other. This simplifies the calculation of post-seismic internal deformation. The numerical results depict that as the degrees increase, the post-seismic DLN reaches stability in a shorter interval of time. Thus, for improved efficiency of the post-seismic internal deformation calculation, the post-seismic DLNs should be calculated within 2000 degree and integrated with the co-seismic results. As an application, the post-seismic Coulomb failure stress changes (ΔCFS) induced by the 2011 Tohoku-Oki earthquake in the near field around the Japanese archipelagos and two major faults in Northeast China were simulated. The results exhibit that the ΔCFS values in the near field agree well with those simulated by the method in a half-space layered earth model, thus verifying the present method. The co-seismic ΔCFS on the Mishan-Dunhua fault in Northeast China, as an example, is only 0.094–0.668 KPa. However, the ΔCFS caused by the viscoelastic relaxation of the mantle within 5 years following the 2011 Tohoku-Oki event on the same fault exceeds the co-seismic results. Therefore, the cumulative effect of the viscoelastic relaxation of the mantle is deserving of attention.

Co-seismic internal deformations in a spherical layered earth model

2020 ◽  
Vol 221 (3) ◽  
pp. 1515-1531
Author(s):  
Tai Liu ◽  
Guangyu Fu ◽  
Yawen She ◽  
Cuiping Zhao
Keyword(s):  
Green's Functions ◽  
Green’S Functions ◽  
Near Field ◽  
Earth Model ◽  
Coulomb Stress ◽  
Far Field ◽  
Coulomb Stress Changes ◽  
Layered Earth ◽  
Stress Changes ◽  
Internal Deformation

SUMMARY Using a numerical integral method, we deduced a set of formulae for the co-seismic internal deformation in a spherically symmetric earth model, simultaneously taking self-gravitation, compressibility and realistically stratified structure of the Earth into account. Using these formulae, we can calculate the internal deformation at an arbitrary depth caused by an arbitrary seismic source. To demonstrate the correctness of our formulae, we compared our numerical solutions of radial functions with analytical solutions reported by Dong & Sun based on a homogeneous earth model; we found that two sets of results agree well with each other. Our co-seismic internal Green's functions in the near field agree well with the results calculated by the formulae of Okada, which also verifies our Green's functions. Finally, we calculated the Coulomb stress changes on the Japanese Islands and Northeast China induced by the Tohoku-Oki Mw 9.0 earthquake using the methods described above. We found that the effect of layered structure plays a leading role on the near field, while curvature occupies a dominant position on the deep region of the far field. Through a comparison of the Coulomb stress changes at a depth of 10 km on a layered earth model calculated by our method along with the corresponding results of Okada, we found that the discrepancy between them in near field was ∼31.5 per cent, and that of far field was >100 per cent of the signals.

scholarly journals Seismic source functions and attenuation from local and teleseismic observations of the NTS events jorum and handley

1981 ◽  
Vol 71 (1) ◽  
pp. 51-67
Author(s):  
Donald V. Helmberger ◽  
David M. Hadley
Keyword(s):  
Near Field ◽  
Strong Motion ◽  
Seismic Source ◽  
Velocity Model ◽  
Test Site ◽  
Earth Model ◽  
Nevada Test Site ◽  
Compressional Waves ◽  
Time Histories ◽  
Source Models

abstract Several strong-motion seismograms recorded at 8 km from a large nuclear test at Pahute Mesa, Nevada Test Site, are modeled using the Cagniard-de Hoop technique. The ratio of vertical to radial motions suggest that the peak values are produced by ray paths that penetrated to a depth several kilometers below the source. A homogeneous layered Earth model with velocity increasing with depth was used in the modeling of the velocity time histories. The upper portion of the velocity model was determined by averaging bore-hole data and the lower portion was obtained from regional refraction measurements. Assuming a modified Haskell (1967) source representation, ψ ( t ) = ψ o [ 1 − e − K t ( 1 + K t + ( K t ) 2 / 2 − B ( K t ) 3 ) ] we obtain a range of source descriptions with ψ0 varying with K and B, ψ0 (K,B). The range of source models for Jorum are ψ0 (5, 1) = 3.1, ψ0 (5, 2) = 1.7, and ψ0 (5, 3) = 1.2 times 1011 cm3, respectively. Given an explosion source description, it is a straightforward task to determine the teleseismic attenuation from WWSSN observations. From both the short- and long-period observations from these events, an average t* of 1.3 is obtained for compressional waves of a dominant 1-sec period. This estimate is insensitive to the range of K and B obtained from the near-field modeling.

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.

Far-field tsunami data assimilation for the 2015 Illapel earthquake

2019 ◽  
Vol 219 (1) ◽  
pp. 514-521 ◽  
Author(s):  
Y Wang ◽  
K Satake ◽  
R Cienfuegos ◽  
M Quiroz ◽  
P Navarrete
Keyword(s):  
Data Assimilation ◽  
Near Field ◽  
Source Parameters ◽  
Deep Ocean ◽  
Seismic Source ◽  
Far Field ◽  
Complementary Method ◽  
East Pacific ◽  
2015 Illapel Earthquake ◽  
Illapel Earthquake

SUMMARY The 2015 Illapel earthquake (Mw 8.3) occurred off central Chile on September 16, and generated a tsunami that propagated across the Pacific Ocean. The tsunami was recorded on tide gauges and Deep-ocean Assessment and Reporting of Tsunami (DART) tsunameters in east Pacific. Near-field and far-field tsunami forecasts were issued based on the estimation of seismic source parameters. In this study, we retroactively evaluate the potentiality of forecasting this tsunami in the far field based solely on tsunami data assimilation from DART tsunameters. Since there are limited number of DART buoys, virtual stations are assumed by interpolation to construct a more complete tsunami wavefront for data assimilation. The comparison between forecasted and observed tsunami waveforms suggests that our method accurately forecasts the tsunami amplitudes and arrival time in the east Pacific. This approach could be a complementary method of current tsunami warning systems based on seismic observations.

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.

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