Slip Distribution of the 1952 Kamchatka Great Earthquake Based on Near-Field Tsunami Deposits and Historical Records

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.

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The waveform inversion of mainshock and aftershock data of the 2006 M6.3 Yogyakarta earthquake

Geoscience Letters ◽

10.1186/s40562-021-00176-w ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Hijrah Saputra ◽

Wahyudi Wahyudi ◽

Iman Suardi ◽

Ade Anggraini ◽

Wiwit Suryanto

Keyword(s):

Joint Inversion ◽

Body Wave ◽

Moment Tensor ◽

Near Field ◽

Source Parameters ◽

Waveform Inversion ◽

Moment Tensor Inversion ◽

Slip Distribution ◽

Aftershock Distribution ◽

Velocity Models

AbstractThis study comprehensively investigates the source mechanisms associated with the mainshock and aftershocks of the Mw = 6.3 Yogyakarta earthquake which occurred on May 27, 2006. The process involved using moment tensor inversion to determine the fault plane parameters and joint inversion which were further applied to understand the spatial and temporal slip distributions during the earthquake. Moreover, coseismal slip distribution was overlaid with the relocated aftershock distribution to determine the stress field variations around the tectonic area. Meanwhile, the moment tensor inversion made use of near-field data and its Green’s function was calculated using the extended reflectivity method while the joint inversion used near-field and teleseismic body wave data which were computed using the Kikuchi and Kanamori methods. These data were filtered through a trial-and-error method using a bandpass filter with frequency pairs and velocity models from several previous studies. Furthermore, the Akaike Bayesian Information Criterion (ABIC) method was applied to obtain more stable inversion results and different fault types were discovered. Strike–slip and dip-normal were recorded for the mainshock and similar types were recorded for the 8th aftershock while the 9th and 16th June were strike slips. However, the fault slip distribution from the joint inversion showed two asperities. The maximum slip was 0.78 m with the first asperity observed at 10 km south/north of the mainshock hypocenter. The source parameters discovered include total seismic moment M0 = 0.4311E + 19 (Nm) or Mw = 6.4 with a depth of 12 km and a duration of 28 s. The slip distribution overlaid with the aftershock distribution showed the tendency of the aftershock to occur around the asperities zone while a normal oblique focus mechanism was found using the joint inversion.

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

10.5194/egusphere-egu2020-22673 ◽

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

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.The waveforms are generated in 3&#8208;D large-scale dynamic rupture simulations which incorporate the interplay of complex fault geometry, topography, 3&#8208;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.&#160;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.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.References:Hanks, T.C., 1980. The corner frequency shift, earthquake source models and Q.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.Wollherr, S., Gabriel, A.-A. and Mai, P.M., 2019.&#160; Landers 1992 &#8220;reloaded&#8221;: Integrative dynamic earthquake rupture modeling. Journal of Geophysical Research: Solid Earth, 124(7), pp.6666-6702.Zhan, Z., 2020. Distributed Acoustic Sensing Turns Fiber&#8208;Optic Cables into Sensitive Seismic Antennas. Seismological Research Letters, 91(1), pp.1-15.

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Self-similar stochastic slip distributions on a non-planar fault for tsunami scenarios for megathrust earthquakes

10.21203/rs.3.rs-32273/v2 ◽

2020 ◽

Author(s):

Masaru Nakano ◽

Shane Murphy ◽

Ryoichiro Agata ◽

Yasuhiko Igarashi ◽

Masato Okada ◽

...

Keyword(s):

Arrival Time ◽

Near Field ◽

Early Warning Systems ◽

Disaster Mitigation ◽

Slip Distribution ◽

Height Distribution ◽

Tsunami Height ◽

Arrival Times ◽

Megathrust Earthquakes ◽

Scenario Earthquakes

Abstract Megathrust earthquakes that occur repeatedly along the plate interface of subduction zones can cause severe damage due to strong ground motion and the destructive tsunamis they can generate. We developed a set of scenario earthquakes to evaluate tsunami hazards and tsunami early warning systems for such devastating earthquakes. Although it is known that the slip distribution on a fault strongly affects the tsunami height distribution in near-field coastal areas, the slip distribution of future earthquakes cannot be exactly predicted. One way to resolve this difficulty is to create a set of scenario earthquakes in which a set of heterogeneous slip distributions on the source fault is stochastically generated based on a given slip probability density function (SPDF). The slip distributions generated in this manner differ from event to event, but their average over a large ensemble of models converges to a predefined SPDF resembling the long-term average of ruptures on the target fault zone. We created a set of SPDF-based scenario earthquakes for an expected future M w 8.2 Tonankai earthquake in the eastern half of the Nankai trough, off southwest Japan, and computed the ensuing tsunamis. We found that the estimated peak coastal amplitudes among the ensemble of tsunamis along the near-field coast differed by factors of 3 to 9 and the earliest and latest arrivals at each observation site differed by 400 to 700 s. The variations in both peak tsunami amplitude and arrival time at each site were well approximated by a Gaussian distribution. For cases in which the slip distribution is unknown, the average and standard deviation of these scenario datasets can provide first approximations of forecast tsunami height and arrival time and their uncertainties, respectively. At most coastal observation sites, tsunamis modelled similarly but using a uniform slip distribution underpredicted tsunami amplitudes but gave earlier arrival times than those modeled with a heterogeneous slip distribution. Use of these earlier arrival times may be useful for providing conservative early warnings of tsunami arrivals. Therefore, tsunami computations for both heterogeneous and uniform slip distributions are important for tsunami disaster mitigation.

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Testing Slip Models for Tsunami Generation

10.5194/egusphere-egu21-13324 ◽

2021 ◽

Author(s):

Hafize Başak Bayraktar ◽

Antonio Scala ◽

Stefano Lorito ◽

Manuela Volpe ◽

Carlos Sánchez Linares ◽

...

Keyword(s):

Subduction Zones ◽

Near Field ◽

Ocean Model ◽

Tsunami Hazard ◽

Slip Distribution ◽

Tsunami Source ◽

Tsunami Observations ◽

The Pacific ◽

Tsunami Waveforms ◽

The Pacific Ocean

Tsunami hazard depends strongly on the slip distribution of a causative earthquake. Simplified uniform slip models lead to underestimating the tsunami wave height which would be generated by a more realistic heterogeneous slip distribution, both in the near-field and in the far-field of the tsunami source. Several approaches have been proposed to generate stochastic slip distributions for tsunami hazard calculations, including in some cases shallow slip amplification (Le Veque et al., 2016; Sepulveda et al., 2017; Davies 2019; Scala et al., 2020). However, due to the relative scarcity of tsunami data, the inter-comparison of these models and the calibration of their parameters against observations is a challenging yet very much needed task, also in view of their use for tsunami hazard assessment.Davies (2019) compared a variety of approaches, which consider both depth-dependent and depth-independent slip models in subduction zones by comparing the simulated tsunami waveforms with DART records of 18 tsunami events in the Pacific Ocean. Model calibration was also proposed by Davies and Griffin (2020).Here, to further progress along similar lines, we compare synthetic tsunamis produced by kinematic slip models obtained with teleseismic inversions from Ye et al. (2016) and by recent stochastic slip generation techniques (Scala et al., 2020) against tsunami observations at open ocean DART buoys, for the same 18 earthquakes and ensuing tsunamis analyzed by Davies (2019). Given the magnitude and location of the real earthquakes, we consider ensembles of consistent slipping areas and slip distributions, accounting for both constant and depth-dependent rigidity models. Tsunami simulations are performed for about 68.000 scenarios in total, using the Tsunami-HySEA code (Mac&#237;as et al., 2016). The simulated results are validated and compared to the DART observations in the same framework considered by Davies (2019).

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A refined slip distribution of the 2013 Mw 6.7 Lushan, China earthquake constrained by GPS and levelling data

Geophysical Journal International ◽

10.1093/gji/ggaa202 ◽

2020 ◽

Vol 222 (1) ◽

pp. 572-581

Author(s):

Yunguo Chen ◽

Kaihua Ding ◽

Qi Wang ◽

Ping He ◽

Shuiping Li ◽

...

Keyword(s):

Fault Plane ◽

Near Field ◽

Focal Depth ◽

Aftershock Sequence ◽

Slip Distribution ◽

Fault System ◽

Gps Data ◽

2008 Wenchuan Earthquake ◽

Spatial Coverage ◽

Tectonic Settings

SUMMARY The 2013 Lushan Mw 6.7 earthquake is the largest blind thrust event ever occurred on the southern segment of the Longmen Shan fault system. It has attracted extensive attention since it occurred 5 yr later following the 2008 Mw 7.8 Wenchuan destructive earthquake in this region. However, its slip distribution is still on debate due to the complex tectonic settings and limited near-field observations. In this study, we added some near-field GPS data, together with previously published GPS data and levelling data, and take consideration of possible coseismic and post-seismic effects caused by the 2008 Wenchuan earthquake, to construct a more accurate horizontal and vertical coseismic surface displacement field associated with the 2013 Lushan earthquake with a better spatial coverage. Then we invert for a refined slip distribution based on a flat-ramp-flat fault suggested by the relocated aftershock sequence and seismic imaging. Our preferred fault plane is striking southwest with 211° and dipping at varying angles of 4°, 35° and 12° separately for such a flat-ramp-flat geometry. The main rupture is roughly characterized by two asperities, including a round disk on the ramp with larger slips and an adjoining oval asperity on the shallow flat with smaller slips. The maximum slip is 1.2 m at 14.3 km focal depth, located at ∼20 km to the northwest of the GCMT epicentre. The released geodetic moment is 1.50 $\ \times $ 1019 Nm, equivalent to a Mw 6.7 earthquake. The slips on the fault plane clearly illustrate that this event is dominated by the thrusting and minor striking, which is consistent with its tectonic settings. Furthermore, if we assume the 2013 Mw 6.7 Lushan event to be the characteristic earthquake on the southern section of the Longmen Shan thrust zone, the accumulated strain should not be fully released by this strong event, and a potential seismic risk still exists in this region.

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Geological and historical evidence of irregular recurrent earthquakes in Japan

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2014.0375 ◽

2015 ◽

Vol 373 (2053) ◽

pp. 20140375 ◽

Cited By ~ 42

Author(s):

Kenji Satake

Keyword(s):

Subduction Zones ◽

Recurrence Interval ◽

Japan Trench ◽

Historical Records ◽

Characteristic Earthquake ◽

Tsunami Deposits ◽

Great Earthquakes ◽

Earthquake Model ◽

Future Earthquake ◽

Simple Characteristic

Great ( M ∼8) earthquakes repeatedly occur along the subduction zones around Japan and cause fault slip of a few to several metres releasing strains accumulated from decades to centuries of plate motions. Assuming a simple ‘characteristic earthquake’ model that similar earthquakes repeat at regular intervals, probabilities of future earthquake occurrence have been calculated by a government committee. However, recent studies on past earthquakes including geological traces from giant ( M ∼9) earthquakes indicate a variety of size and recurrence interval of interplate earthquakes. Along the Kuril Trench off Hokkaido, limited historical records indicate that average recurrence interval of great earthquakes is approximately 100 years, but the tsunami deposits show that giant earthquakes occurred at a much longer interval of approximately 400 years. Along the Japan Trench off northern Honshu, recurrence of giant earthquakes similar to the 2011 Tohoku earthquake with an interval of approximately 600 years is inferred from historical records and tsunami deposits. Along the Sagami Trough near Tokyo, two types of Kanto earthquakes with recurrence interval of a few hundred years and a few thousand years had been recognized, but studies show that the recent three Kanto earthquakes had different source extents. Along the Nankai Trough off western Japan, recurrence of great earthquakes with an interval of approximately 100 years has been identified from historical literature, but tsunami deposits indicate that the sizes of the recurrent earthquakes are variable. Such variability makes it difficult to apply a simple ‘characteristic earthquake’ model for the long-term forecast, and several attempts such as use of geological data for the evaluation of future earthquake probabilities or the estimation of maximum earthquake size in each subduction zone are being conducted by government committees.

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The waveform inversion of mainshock and aftershock data of the 2006 M6.3 Yogyakarta earthquake

10.21203/rs.3.rs-36861/v2 ◽

2021 ◽

Author(s):

Hijrah Saputra ◽

Wahyudi Wahyudi ◽

Iman Suardi ◽

Ade Anggraini ◽

Wiwit Suryanto

Keyword(s):

Joint Inversion ◽

Body Wave ◽

Moment Tensor ◽

Near Field ◽

Source Parameters ◽

Moment Tensor Inversion ◽

Slip Distribution ◽

Coseismic Slip ◽

Aftershock Distribution ◽

Velocity Models

Abstract This study comprehensively investigates the source mechanisms associated with the mainshock and aftershocks of the Yogyakarta earthquake of magnitude Mw = 6.3 on May 27, 2006. Therefore, this study is to provide a more precise answer to the controversial source mechanism. This study uses moment tensor inversion to obtain fault plane parameters and joint inversion to obtain spatial and temporal slip distributions during an earthquake. The coseismic slip distribution is overlaid with the relocated aftershock distribution to see the stress field variations around the tectonic area of the study. Moment tensor inversion uses near-field data, and joint inversion uses near-field and teleseismic body wave data. The data is filtered by trial and error using a bandpass filter with frequency pairs and velocity models from several previous studies. The green's function for moment tensor inversion calculated using the extended reflectivity method and joint inversion computed using the Kikuchi and Kanamori methods. In this study, we apply the Akaike Bayesian Information Criterion (ABIC) method to obtain more stable inversion results. The results of the mainshock and aftershock moment tensor inversion show different fault types. The mainshock fault types are strike-slip and dip-normal types, while the 8th aftershock is of the same type as the mainshock, while the 9th and 16th June are strike slips. The joint inversion results show two asperities. The maximum slip is 0.78 m, with the first asperity 10 km south of the mainshock and the second asperity 10 km north of the mainshock. The obtained source parameters are total seismic moment M0 = 0.4311E + 19 (Nm) or Mw = 6.4, with a source depth of 12 km and a source duration of 28 seconds. Slip distribution overlay with aftershock distribution shows compatibility. The type of focus mechanism that results from this joint inversion is the oblique.

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Self-similar stochastic slip distributions on a non-planar fault for tsunami scenarios for megathrust earthquakes

10.21203/rs.3.rs-32273/v1 ◽

2020 ◽

Author(s):

Masaru Nakano ◽

Shane Murphy ◽

Ryoichiro Agata ◽

Yasuhiko Igarashi ◽

Masato Okada ◽

...

Keyword(s):

Arrival Time ◽

Near Field ◽

Early Warning Systems ◽

Disaster Mitigation ◽

Slip Distribution ◽

Height Distribution ◽

Tsunami Height ◽

Arrival Times ◽

Megathrust Earthquakes ◽

Scenario Earthquakes

Abstract Megathrust earthquakes that occur repeatedly along the plate interface of subduction zones can cause severe damage due to strong ground motion and the destructive tsunamis they can generate. We developed a set of scenario earthquakes to evaluate tsunami hazards and tsunami early warning systems for such devastating earthquakes. Although it is known that the slip distribution on a fault strongly affects the tsunami height distribution in near-field coastal areas, the slip distribution of future earthquakes cannot be exactly predicted. One way to resolve this difficulty is to create a set of scenario earthquakes in which a set of heterogeneous slip distributions on the source fault is stochastically generated based on a given slip probability density function (SPDF). The slip distributions generated in this manner differ from event to event, but their average over a large ensemble of models converges to a predefined SPDF resembling the long-term average of ruptures on the target fault zone. We created a set of SPDF-based scenario earthquakes for an expected future Mw 8.2 Tonankai earthquake in the eastern half of the Nankai trough, off southwest Japan, and computed the ensuing tsunamis. We found that the estimated peak coastal amplitudes among the ensemble of tsunamis along the near-field coast differed by factors of 3 to 9 and the earliest and latest arrivals at each observation site differed by 400 to 700 s. The variations in both peak tsunami amplitude and arrival time at each site were well approximated by a Gaussian distribution. For cases in which the slip distribution is unknown, the average and standard deviation of these scenario datasets can provide first approximations of forecast tsunami height and arrival time and their uncertainties, respectively. At most coastal observation sites, tsunamis modelled similarly but using a uniform slip distribution underpredicted tsunami amplitudes but gave earlier arrival times than those modeled with a heterogeneous slip distribution. Use of these earlier arrival times may be useful for providing conservative early warnings of tsunami arrivals. Therefore, tsunami computations for both heterogeneous and uniform slip distributions are important for tsunami disaster mitigation.

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Quasi-real-time on-fault heterogeneous slip distributions for tsunami early warning purposes

10.5194/egusphere-egu2020-10505 ◽

2020 ◽

Author(s):

Alberto Armigliato ◽

Enrico Baglione ◽

Stefano Tinti

Keyword(s):

Real Time ◽

Early Warning ◽

Fault Plane ◽

Near Field ◽

Slip Distribution ◽

Slip Model ◽

Fault Models ◽

Tsunami Early Warning ◽

Finite Fault ◽

Run Up

The study presented here takes the move from two well-known premises in tsunami science: the slip distribution on earthquake faults is heterogeneous and, in the case of tsunamigenic earthquakes, slip heterogeneity influences significantly the distribution of tsunami run-ups, especially for near-field areas. In the perspective of tsunami early warning, a crucial issue is to obtain a reasonable slip distribution within a time significantly shorter than the time taken by the waves to impact the nearest coastlines.When an earthquake occurs, the only information that becomes available after a few minutes concerns the location of the earthquake and its magnitude. The first finite-fault models (FFM), based on seismic/geodetic data inversion, become available several hours or even days after the earthquake origin time. In the case of tsunamigenic earthquakes, tsunami waveforms useful for inversion become available after the tsunami passage at the recording stations. From the warning perspective, the time to get FFM representations is therefore too long for the near-source coastal areas. We propose and describe a strategy whose goal is to derive in quasi-real-time a reasonable representation of the heterogeneous slip distribution on the fault responsible for a given tsunamigenic earthquake and to forecast the run-up distribution along the nearest coastlines. The strategy is illustrated in its application to the 16 September 2015 Illapel (Chile) tsunamigenic earthquake.Realistically, the hypocentre location and the magnitude of the event can be available within two-three minutes. Knowing the hypocentre location permits us to place the fault plane in a definite geographical reference, while the knowledge of magnitude allows to derive the fault dimension and the slip model. A key point here is that we can derive slip models only knowing the magnitude and the location of the hypocenter. Among these models, we adopt simple 2D Gaussian Distributions (GDs), representing the main asperity, whose parameters can be deduced from properly defined regression laws. The 2D-GD simple representation takes a very short time to be derived. To complete the characterization of the tsunamigenic source, focal parameters can be safely derived from seismological databases, while the position of the fault represents a trickier point, as the fault plane is not necessarily centered at the earthquake hypocentre. To take this uncertainty into account, as a first approach three faults for each slip model are considered: 1) a plane centered on the hypocentre, 2) a fault shifted northwards, 3) a fault shifted southwards. We run tsunami simulations for each adopted slip distribution and for each fault position, and compare the results against the available observed tide-gauge and run-up data in the near-field. We compare the performance of our 2D-GD models with respect to the finite-fault models retrieved from inversion procedures, published months after the 2015 event. We demonstrate that the 2D-GD method performs very satisfactorily in comparison to more refined, non-real-time published FFMs and hence permits to produce reliable real-time tsunami simulations very quickly and can be used as an experimental procedure in the frame of operational tsunami warning systems.

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