Seismological Constraints on Fault-Slip Source Models and Rupture Characteristics of Global Large Earthquakes (Mw ≥ 7.5) and Associated Tsunamis

2020 ◽  
Author(s):  
Seda Yolsal-Çevikbilen ◽  
Tuncay Taymaz
Keyword(s):  
Near Field ◽  
Fault Slip ◽  
Earthquake Source ◽  
P Wave ◽  
Slip Distribution ◽  
Distribution Models ◽  
Tsunami Waves ◽  
Source Mechanisms ◽  
Source Models ◽  
Large Earthquakes

<p>Large and destructive earthquakes (M<sub>w</sub>≥ 7.5) occur worldwide particularly along the major subduction zones causing extensive damage and loss of life in the hinterland of epicentral region. Source models and rupture characteristics of these earthquakes (i.e. faulting geometry, focal depth, non-uniform finite-fault slip distributions) can be precisely determined by using seismological data and multidisciplinary earth-science observations. It is also known that earthquake source parameters play key roles in the modelling of secondary events such as earthquake-induced tsunamis. There are many studies emphasizing the importance of using heterogonous slip distribution models of earthquakes in mathematical tsunami simulations to predict synthetic tsunami waves more consistent with the observed ones. In this study, we obtained double-couple source mechanisms and slip distribution models of complex large earthquakes (M<sub>w</sub>≥ 7.5) lately occurred at different parts of the Earth. For this purpose, we used point-source teleseismic P- and SH- body waveform inversion and kinematic slip distribution inversion techniques. Besides, azimuthal distributions of P- wave first motion polarities, which are recorded by near-field and regional seismic stations, are checked to approve obtained minimum misfit source mechanism parameters of earthquakes. We essentially observed that tsunamigenic earthquakes occurred at shallow focal depths (h ≤ 70 km) with dip-slip source mechanisms and rather complex slip distributions along the fault planes. However, in some cases, tsunami waves may be unexpectedly triggered due to the secondary effects of large strike-slip earthquakes (e.g., September 28, 2018 Palu, Indonesia - M<sub>w</sub>7.5). Here, we discuss our inversion results, which reveal the significant contributions of earthquake source studies on resolving the relationships between the faulting geometry, rupture characteristics and tsunami generation. Furthermore, the necessity of high-resolution bathymetry data in numerical tsunami simulations is highlighted for the modelling of tsunami waves, in particular, recorded at the near-field tide-gauge stations. This study is partially supported by the Turkish Academy of Sciences (TÜBA) through GEBIP program.</p>

Dense surface seismic data confirm non-double-couple source mechanisms induced by hydraulic fracturing

Geophysics ◽  
2016 ◽  
Vol 81 (6) ◽  
pp. KS207-KS217 ◽  
Author(s):  
Jeremy D. Pesicek ◽  
Konrad Cieślik ◽  
Marc-André Lambert ◽  
Pedro Carrillo ◽  
Brad Birkelo
Keyword(s):  
Hydraulic Fracturing ◽  
Seismic Data ◽  
P Wave ◽  
Source Modeling ◽  
Moment Tensors ◽  
Amplitude Data ◽  
Double Couple ◽  
Source Mechanisms ◽  
Source Models ◽  
Favorable Conditions

We have determined source mechanisms for nine high-quality microseismic events induced during hydraulic fracturing of the Montney Shale in Canada. Seismic data were recorded using a dense regularly spaced grid of sensors at the surface. The design and geometry of the survey are such that the recorded P-wave amplitudes essentially map the upper focal hemisphere, allowing the source mechanism to be interpreted directly from the data. Given the inherent difficulties of computing reliable moment tensors (MTs) from high-frequency microseismic data, the surface amplitude and polarity maps provide important additional confirmation of the source mechanisms. This is especially critical when interpreting non-shear source processes, which are notoriously susceptible to artifacts due to incomplete or inaccurate source modeling. We have found that most of the nine events contain significant non-double-couple (DC) components, as evident in the surface amplitude data and the resulting MT models. Furthermore, we found that source models that are constrained to be purely shear do not explain the data for most events. Thus, even though non-DC components of MTs can often be attributed to modeling artifacts, we argue that they are required by the data in some cases, and can be reliably computed and confidently interpreted under favorable conditions.

Near-field spectral analysis of data-integrative dynamic rupture earthquake simulations of the 1992 Landers earthquake

2020 ◽  
Author(s):  
Nico Schliwa ◽  
Alice-Agnes Gabriel
Keyword(s):  
Spectral Analysis ◽  
Ground Motion ◽  
Near Field ◽  
Slip Distribution ◽  
Corner Frequency ◽  
Dynamic Rupture ◽  
Geophysical Research ◽  
Acoustic Sensing ◽  
Distributed Acoustic Sensing ◽  
Large Earthquakes

<p>The rise of observations from Distributed Acoustic Sensing (e.g., Zhan 2020) and high-rate GNSS networks (e.g., Madariaga et al., 2019) highlight the potential of dense ground motion observations in the near-field of large earthquakes. Here, spectral analysis of >100,000 synthetic near-field strong motion waveforms (up to 2 Hz) is presented in terms of directivity, corner frequency, fall-off rate, moment estimates and static displacements.</p><p>The waveforms are generated in 3‐D large-scale dynamic rupture simulations which incorporate the interplay of complex fault geometry, topography, 3‐D rheology and viscoelastic attenuation (Wollherr et al., 2019). A preferred scenario accounts for off-fault deformation and reproduces a broad range of observations, including final slip distribution, shallow slip deficits, and spontaneous rupture termination and transfers between fault segments. We examine the effects of variations in modeling parameterization within a suite of scenarios including purely elastic setups and models neglecting viscoelastic attenuation. </p><p>First, near-field corner frequency mapping implementing a novel spectral seismological misfit criterion reveals rays of elevated corner frequencies radiating from each slipping fault at 45 degree to rupture forward direction. The azimuthal spectral variations are specifically dominant in the vertical components indicating we map rays of direct P-waves prevailing (Hanks, 1980). The spatial variation in corner frequencies carries information on co-seismic fault segmentation, slip distribution, focal mechanisms and stress drop. Second, spectral fall-off rates are variably inferred during picking the associated corner frequencies to identify the crossover from near-field to far-field spectral behaviour in dependence on distance and azimuth. Third, we determine static displacements with the help of near-field seismic spectra.</p><p>Our findings highlight the future potential of spectral analysis of spatially dense (low frequency) ground motion observations for inferring earthquake kinematics and understanding earthquake physics directly from near-field data; while synthetic studies are crucial to identify "what to look for" in the vast amount of data generated.</p><p><em>References:</em></p><p>Hanks, T.C., 1980. The corner frequency shift, earthquake source models and Q.</p><p>Madariaga, R., Ruiz, S., Rivera, E., Leyton, F. and Baez, J.C., 2019. Near-field spectra of large earthquakes. Pure and Applied Geophysics, 176(3), pp.983-1001.</p><p>Wollherr, S., Gabriel, A.-A. and Mai, P.M., 2019.  Landers 1992 “reloaded”: Integrative dynamic earthquake rupture modeling. Journal of Geophysical Research: Solid Earth, 124(7), pp.6666-6702.</p><p>Zhan, Z., 2020. Distributed Acoustic Sensing Turns Fiber‐Optic Cables into Sensitive Seismic Antennas. Seismological Research Letters, 91(1), pp.1-15.</p>

Present Seismotectonic Behavior of the EAF from Improved Seismicity Catalog and Earthquake Source Mechanism Solutions

2020 ◽  
Author(s):  
Sezim Ezgi Guvercin ◽  
Hayrullah Karabulut ◽  
Ugur Dogan ◽  
Ziyadin Cakir ◽  
Semih Ergintav ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Complex Structure ◽  
Slip Rate ◽  
Earthquake Source ◽  
Slip Rates ◽  
North East ◽  
The North ◽  
Source Mechanisms ◽  
Seismicity Catalog ◽  
Large Earthquakes

<p>The seismotectonic behavior of the Eastern Anatolia is predominantly controlled by the East Anatolian Fault (EAF). Together with the North Anatolian Fault (NAF), this ~400 km long sinistral transform fault, accommodates the westward motion of Anatolia between Anatolian and Arabian plates with a slip rate of ~10 mm/yr which is significantly slower than the motion of the NAF (25 mm/yr). Although this two major faults are similar in terms of the migration of the large earthquakes from east to west, the present seismicity of the EAF is high compared to the NAF. Except for the several earthquakes with Mw > 5, there were no devastating earthquakes during the instrumental period along the EAF. The absence of large earthquakes during the last ~50 years along the EAF indicates presence of significant seismic gaps and potential seismic hazard in the region. Recent studies indicate segmentation of the EAF with varying lengths of creeping and locked segments. Some details of the geometries and the slip rates of these segments have been estimated by the InSAR observations. Both InSAR and GPS observations indicate that the maximum creep along this the EAF is ~10 mm/yr, approximately the slip rate of the EAF.</p><p>While both geodetic data verify the existence of creep from surface deformation, its relation to the seismic behavior of the EAF is less clear. There is a ~30 km long creeping segment to the north-east of Lake Hazar which generates no significant seismicity. On the other hand, another creeping segment to the south-west of Lake Hazar, there are repeating events, below the depth of 10 km, with a horizontal extent of 15 km. The highly fractured and complex structure of this fault zone is also confirmed by the available focal mechanisms which shows significant variety.</p><p>In this study, we update seismicity catalog with improved locations to date and present a uniform and high quality focal mechanism catalog down to M4 completeness, using regional waveforms. The seismicity catalog is used to estimate the geometry of the segmentation while the novel earthquake source mechanisms are used to understand the kinematics of the segments and interactions. Moreover, we present the latest M4.9, 2019, Sivrice earthquake, pointing out a location where the stress is perturbed due to a transition from creeping segment to locked segment. (Supported by TUBITAK no: 118Y435 project)</p>

scholarly journals Assessment of the peak tsunami amplitude associated with a large earthquake occurring along the southernmost Ryukyu subduction zone in the region of Taiwan

2018 ◽  
Vol 18 (8) ◽  
pp. 2081-2092
Author(s):  
Yu-Sheng Sun ◽  
Po-Fei Chen ◽  
Chien-Chih Chen ◽  
Ya-Ting Lee ◽  
Kuo-Fong Ma ◽  
...  
Keyword(s):  
Near Field ◽  
Large Earthquake ◽  
Slip Distribution ◽  
Tsunami Source ◽  
Wave Number ◽  
Potential Region ◽  
Earthquake Scenario ◽  
Tsunami Waves ◽  
Rupture Length ◽  
Tsunami Amplitude

Abstract. The southernmost portion of the Ryukyu Trench near the island of Taiwan potentially generates tsunamigenic earthquakes with magnitudes from 7.5 to 8.7 through shallow rupture. The fault model for this potential region dips 10∘ northward with a rupture length of 120 km and a width of 70 km. An earthquake magnitude of Mw 8.15 is estimated by the fault geometry with an average slip of 8.25 m as a constraint on the earthquake scenario. Heterogeneous slip distributions over the rupture surface are generated by a stochastic slip model, which represents the decaying slip spectrum according to k−2 in the wave number domain. These synthetic slip distributions are consistent with the abovementioned identical seismic conditions. The results from tsunami simulations illustrate that the propagation of tsunami waves and the peak wave heights largely vary in response to the slip distribution. Changes in the wave phase are possible as the waves propagate, even under the same seismic conditions. The tsunami energy path not only follows the bathymetry but also depends on the slip distribution. The probabilistic distributions of the peak tsunami amplitude calculated by 100 different slip patterns from 30 recording stations reveal that the uncertainty decreases with increasing distance from the tsunami source. The highest wave amplitude for 30 recording points is 7.32 m at Hualien for 100 different slips. Compared with the stochastic-slip distributions, the uniform slip distribution will be highly underestimated, especially in the near field. In general, the uniform slip assumption only represents the average phenomenon and will consequently ignore the possibility of tsunami waves. These results indicate that considering the effects of heterogeneous slip distributions is necessary for assessing tsunami hazards to provide additional information about tsunami uncertainties and facilitate a more comprehensive estimation.

scholarly journals Assessment of peak tsunami amplitude associated with a great earthquake occurring along the southernmost Ryukyu subduction zone for Taiwan region

2017 ◽  
Author(s):  
Yu-Sheng Sun ◽  
Po-Fei Chen ◽  
Chien-Chih Chen ◽  
Ya-Ting Lee ◽  
Kuo-Fong Ma ◽  
...  
Keyword(s):  
Near Field ◽  
Slip Distribution ◽  
Tsunami Source ◽  
Wave Number ◽  
Great Earthquake ◽  
Potential Region ◽  
Earthquake Scenario ◽  
Tsunami Waves ◽  
Rupture Length ◽  
Tsunami Amplitude

Abstract. The southernmost portion of the Ryukyu Trench closed to Taiwan island is a potential region to generate 7.5 to 8.7 tsunami earthquakes by shallow rupture. The fault model for this potential region dips 10º northward with rupture length of 120 km and width of 70 km. The earthquake magnitude estimated by fault geometry is Mw 8.15 with 8.25 m average slip as a constrain of earthquake scenario. The heterogeneous slip distributions over rupture surface are generated by stochastic slip model, the slip spectrum with k-2 decay in wave number domain, and they are consistent with above identical seismic conditions. The results from tsunami simulation illustrate that the propagation of tsunami waves and the peak wave heights largely vary in response to the slip distribution. The wave phase changing is possible as the waves propagate, even under the same seismic conditions. The tsunami energy path is not only following the bathymetry but also depending on slip distribution. The probabilistic distributions of peak tsunami amplitude calculated by 100 different slip patterns from 30 recording stations reveal the uncertainty decreases with distance from tsunami source. The highest wave amplitude for 30 recording points is 7.32 m at Hualien for 100 different slips. Comparing with stochastic slips, uniform slip distribution will be extremely underestimated, especially in near field. In general, uniform slip assumption only represents the average phenomenon so that it will ignore possibility of tsunami wave. These results indicate that considering effect of heterogeneous slip distribution is necessary for assessing tsunami hazard and that can provide more information about tsunami uncertainty for a more comprehensive estimation.

The 2017 November 12 Mw 7.3 Sarpol-Zahab (Iran-Iraq border region) earthquake: source model, aftershock sequence and earthquakes triggering

2020 ◽  
Author(s):  
Mohammadreza Jamalreyhani ◽  
Mehdi Rezapour ◽  
Simone Cesca ◽  
Sebastian Heimann ◽  
Hannes Vasyura-Bathke ◽  
...  
Keyword(s):  
Fault Plane ◽  
Joint Inversion ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Fault Slip ◽  
Earthquake Source ◽  
Border Region ◽  
Model Parameters ◽  
Fault Geometry ◽  
Large Earthquakes

<p>The Mw 7.3 Sarpol-Zahab earthquake occurred on 12 November 2017 in the Lurestan arc of the Zagros Simply Folded Belt (ZSFB). It is estimated that 600 people were killed and 8000 were injured in this earthquake. This earthquake has been the largest instrumentally recorded earthquake in the ZSFB and its moment, as well as its mechanism, were unexpected. We present an earthquake source study on the Mw 7.3 Sarpol-Zahab earthquake, two large following earthquakes in the region in 2018 and their corresponding aftershock sequences to gain insight of seismotectonic of the Lurestan arc fold-thrust belt.</p><p>In this study, we complement previous studies on this earthquake, by non-linear probabilistic optimization of joined geodetic and seismic data using a new, efficient Bayesian bootstrap-based optimization scheme to infer the finite fault geometry and fault slip together with meaningful uncertainty estimates of the model parameters. Our optimization is based on the modeling of ascending and descending Sentinel-1 satellite data, seismological waveform from global seismic networks and the strong motion network of Iran. The posterior mean model of the Sarpol-Zahab earthquake shows that the causative fault plane is centered at is 14±2 km depth and has a low dip angle of 17°±2° and a strike of 350°±10°. The rake angle of 144°±4° points to an oblique thrust mechanism. The rupture area of the uniform-slip, rectangular model is 40±2 km long and 16±2 km width and shows 4.0±0.5 m fault slip, which results in a magnitude estimate of Mw 7.3±0.1.</p><p>Later, in August and November 2018, two large earthquakes with Mw 6.0 and Mw 6.4 occurred about 40 km east and 60 km south of the Sarpol-Zahab epicenter, respectively. These earthquakes could have been triggered by the 2017 Sarpol-Zahab earthquake. We apply the same joint inversion modeling to derive the corresponding fault plane solutions. We found strike-slip mechanisms for both events but centroid depths at 10±2 km and 16±2 km for Mw 6.0 and Mw 6.4, respectively.</p><p>The 2017 Sarpol-Zahab earthquake and the following studied 2018 earthquakes were followed by a sustained aftershock sequence, with more than 133 aftershocks exceeding Ml 4.0 until December 30, 2019. We rely on the local and regional seismic broad-band stations of Iran and Iraq permanent networks to estimate full-waveform moment tensor solutions of 70 aftershocks down to Ml 4. Most of these aftershocks have shallow centroid depths between 5 and 12 km, so that they occurred in the uppermost part of the basement and/or in the lower sedimentary cover, which is ~8 km thick in this area.</p><p>Our results suggest that the Sarpol-Zahab earthquakes activated low-angle thrust faults and shallower strike-slip structures, highlighting that both thin- and thick-skin deformation take place in the fold-thrust belts in the Lurestan arc of the Zagros. Such information on the deformation characteristics is important for the hazard and risk assessment of future large earthquakes in this region.<br>Additionally, we demonstrate how the joint inversion of different geophysical data can help to better resolve the fault geometry and the earthquake source parameters.</p>

FAULT SLIP DISTRIBUTION ALONG THE SOUTHERN 15 KM OF THE M7.1 RIDGECREST EARTHQUAKE SURFACE RUPTURE

2020 ◽  
Author(s):  
Sinan O. Akciz ◽  
◽  
Salena Padilla ◽  
James F. Dolan ◽  
Alex E. Hatem
Keyword(s):  
Fault Slip ◽  
Slip Distribution ◽  
Surface Rupture ◽  
Fault Slip Distribution

scholarly journals Coseismic fault-slip distribution of the 2019 Ridgecrest Mw6.4 and Mw7.1 earthquakes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yang Gao ◽  
HuRong Duan ◽  
YongZhi Zhang ◽  
JiaYing Chen ◽  
HeTing Jian ◽  
...  
Keyword(s):  
Strike Slip ◽  
Fault Slip ◽  
Slip Distribution ◽  
Synthetic Aperture ◽  
Seismic Events ◽  
Interferometric Synthetic Aperture Radar ◽  
The Past ◽  
Dextral Strike Slip Fault ◽  
Fault Slip Distribution ◽  
Dextral Strike Slip

AbstractThe 2019 Ridgecrest, California seismic sequence, including an Mw6.4 foreshock and Mw7.1 mainshock, represent the largest regional seismic events within the past 20 years. To obtain accurate coseismic fault-slip distribution, we used precise positioning data of small earthquakes from January 2019 to October 2020 to determine the dip parameters of the eight fault geometry, and used the Interferometric Synthetic Aperture Radar (InSAR) data processed by Xu et al. (Seismol Res Lett 91(4):1979–1985, 2020) at UCSD to constrain inversion of the fault-slip distribution of both earthquakes. The results showed that all faults were sinistral strike-slips with minor dip-slip components, exception for dextral strike-slip fault F2. Fault-slip mainly occurred at depths of 0–12 km, with a maximum slip of 3.0 m. The F1 fault contained two slip peaks located at 2 km of fault S4 and 6 km of fault S5 depth, the latter being located directly above the Mw7.1hypocenter. Two slip peaks with maximum slip of 1.5 m located 8 and 20 km from the SW endpoint of the F2 fault were also identified, and the latter corresponds to the Mw6.4 earthquake. We also analyzed the influence of different inversion parameters on the fault slip distribution, and found that the slip momentum smoothing condition was more suitable for the inversion of the earthquakes slip distribution than the stress-drop smoothing condition.

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