Limitations of the Resolvability of Finite‐Fault Models Using Static Land‐Based Geodesy and Open‐Ocean Tsunami Waveforms

2018 ◽  
Vol 123 (10) ◽  
pp. 9033-9048 ◽  
Author(s):  
Amy L. Williamson ◽  
Andrew V. Newman
Keyword(s):  
Open Ocean ◽  
Fault Models ◽  
Finite Fault ◽  
Tsunami Waveforms

Finite Fault Modelling for the Wenchuan Earthquake Using Hybrid Slip Model with Truncated Normal Distributed Source Parameters

2012 ◽  
Vol 256-259 ◽  
pp. 2161-2167 ◽  
Author(s):  
Xiao Dan Sun ◽  
Xia Xin Tao ◽  
Cheng Qing Liu
Keyword(s):  
Wenchuan Earthquake ◽  
Ground Motion ◽  
Source Parameters ◽  
Field Investigation ◽  
Local Source ◽  
Slip Model ◽  
Fault Models ◽  
Average Spectrum ◽  
Finite Fault ◽  
Truncated Normal

An hybrid slip model combining asperity model and k square model was outlined. In the model, both the global and local source parameters follow a trancated normal distribution. The hybrid slip model was then applied to generate finite fault models for the great Wenchuan earthquake, where the fault plane was assumed to have two segments, a reverse segment on the southwestern of the fault and a right-lateral strike-slip segment on the northeastern of the fault. The location of the asperities on each segment was determined considering the results from inversion and field investigation. 30 different finite fault models were obtained, and the one which generates the ground motion best fitting the average spectrum was picked out using spectral deviation evaluation. Finally, ground motion at six near field stations were simualted based on the best-fit fault model and compared to the records.

scholarly journals Automatic Inversions of Strong‐Motion Records for Finite‐Fault Models of Significant Earthquakes in and Around Japan

2020 ◽  
Vol 125 (9) ◽  
Author(s):  
Xujun Zheng ◽  
Yong Zhang ◽  
Rongjiang Wang ◽  
Li Zhao ◽  
Wenying Li ◽  
...  
Keyword(s):  
Strong Motion ◽  
Fault Models ◽  
Strong Motion Records ◽  
Finite Fault

Real-Time Tsunami Inundation Forecast for a Recurrence of 17thCentury Great Hokkaido Earthquake in Japan

2014 ◽  
Vol 9 (3) ◽  
pp. 358-364 ◽  
Author(s):  
Yuichiro Tanioka ◽  
◽  
Aditya Riadi Gusman ◽  
Kei Ioki ◽  
Yugo Nakamura
Keyword(s):  
Real Time ◽  
Pacific Coast ◽  
Great Earthquake ◽  
Tsunami Deposit ◽  
Fault Models ◽  
Fine Grid ◽  
Tsunami Inundation ◽  
Inundation Area ◽  
The Pacific ◽  
Tsunami Waveforms

Paleotsunami studies have shown that several large tsunamis hit the Pacific coast. Many tsunami deposit data were available for the 17thcentury tsunami. The most recent tsunami deposit study in 2013 indicated that the large slip of about 25 m along the plate interface near the Kurile trench would be necessary and the seismic moment of this 17thcentury earthquake was 1.7 × 1022Nm. If a great earthquake like the 17thcentury earthquake occurs off the Pacific coast of Hokkaido, the devastating disaster along the coast is expected. To minimize the tsunami disaster, a development of the real-time forecast of a tsunami inundation area is necessary. Estimating a tsunami inundation area requires tsunami numerical simulation with a very fine grid system of less than 1 arcsecond. There is not enough time to compute the tsunami inundation area after a large earthquake occurs. In this study, we develop a real-time tsunami inundation forecast method using a database including many tsunami inundation areas previously computed using various fault models. After great earthquakes, tsunamis are computed using linear long-wave equations for fault models estimated in real time. Simulating such tsunamis takes only 1-3 minutes on a typical PC, so it is potentially useful for forecasting tsunamis. Tsunami inundation areas computed numerically using various fault models and tsunami waveforms at several locations near the inundation area are stored in a database. Those computed tsunami waveforms are used to choose the most appropriate tsunami inundation area by comparing them to the tsunami waveforms computed in real time. This method is tested at Kushiro, a city in Hokkaido. We found that the method worked well enough to forecast the Kushiro’s tsunami inundation area.

Real-Time GNSS Analysis System REGARD: An Overview and Recent Results

2018 ◽  
Vol 13 (3) ◽  
pp. 440-452 ◽  
Author(s):  
Satoshi Kawamoto ◽  
Naofumi Takamatsu ◽  
Satoshi Abe ◽  
Kohei Miyagawa ◽  
Yusaku Ohta ◽  
...  
Keyword(s):  
Real Time ◽  
Tohoku Earthquake ◽  
Satellite System ◽  
Fault Models ◽  
The 2011 Tohoku Earthquake ◽  
Model Inversion ◽  
Finite Fault ◽  
Analysis System ◽  
Global Navigation Satellite ◽  
Large Earthquakes

A new real-time Global Navigation Satellite System (GNSS) analysis system named REGARD has been launched to provide finite-fault models for large earthquakes with magnitudes =8 in real time. The finite-fault estimates using GNSS positioning are free from saturation problems and are very robust for modeling large earthquakes. The REGARD system processes ∼1,200 stations of GEONET, and event detection and finite-fault model inversion routines are implemented. Tests for the case of the 2011 Tohoku earthquake (Mw9.0) and a simulated Nankai Trough earthquake (Mw8.7) show that the REGARD system can provide reliable finite-fault models for large earthquakes. Furthermore, operational real-time results for the 2016 Kumamoto earthquake (Mj7.3) demonstrated the capability of this system to model inland earthquakes. These results imply the possibility of improving tsunami simulations and/or hazard information using rapid finite-fault models. Efforts to integrate real-time GNSS with current warning systems are currently being implemented around the world, and the REGARD system will join these systems in the near future.

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

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

<p><span>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.</span></p><p><span>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. </span></p><p><span>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.</span></p><p><span>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. </span></p><p><span>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. </span></p>

Earthquake‐Scaling Relationships from Geodetically Derived Slip Distributions

2019 ◽  
Vol 109 (5) ◽  
pp. 1701-1715 ◽  
Author(s):  
Clayton M. J. Brengman ◽  
William D. Barnhart ◽  
Emma H. Mankin ◽  
Cody N. Miller
Keyword(s):  
Moment Magnitude ◽  
Earthquake Rupture ◽  
Fault Models ◽  
Model Resolution ◽  
Scaling Relationships ◽  
Rupture Area ◽  
Finite Fault ◽  
Earthquake Scaling ◽  
Shape Characteristics ◽  
Fault Length

Abstract Empirical earthquake scaling relationships describe expected relationships between moment magnitude and various spatial descriptors of the earthquake rupture (along‐strike length, down‐dip width, rupture area, and peak and mean slip). These scaling relationships play important roles in many seismological, geological, and hazards‐assessment applications. Historically, scaling relationships were defined from various seismological criteria, such as teleseismic finite‐fault models or aftershock distributions. The proliferation of earthquake slip distributions from geodetic observations presents an opportunity to reassess earthquake scaling relationships using observations that more directly sample the spatial characteristics of an earthquake than seismological observations. Here, we present a database of 111 earthquake slip distributions from 73 different earthquakes that were derived from geodetic observations. The earthquakes range in magnitude from Mw 5.3 to 9.1. We extract common spatial descriptors from these slip distributions in four different ways to account for biases introduced by inversion regularization, and we regress these spatial descriptors with moment magnitude to derive new empirical scaling relationships. We additionally assess the shape characteristics of the slip distributions and report the average earthquake shape. We find that our scaling relationships differ in important ways from previous studies, and we show that these differences originate from our use of a geodetic slip‐distribution database rather than from methods for extracting spatial descriptors. Notably, we find that geodetic slip distributions systematically predict smaller fault areas than seismically derived scaling relationships. Because geodetic source inversions are likely contaminated to some degree by aseismic afterslip, this relationship suggests that seismologically determined scaling relationships systematically overpredict earthquake dimensions. We find that fault length, fault width, peak slip, and mean slip differ from previous studies in ways that are more complex and magnitude dependent. Given the high‐model resolution afforded by geodetic observations, our earthquake scaling relationships derived from geodetic slip distributions provide improved constraints on empirical scaling relationships.

scholarly journals Benchmarking the Optimal Time Alignment of Tsunami Waveforms in Nonlinear Joint Inversions for the Mw 8.8 2010 Maule (Chile) Earthquake

2020 ◽  
Vol 8 ◽  
Author(s):  
F. Romano ◽  
S. Lorito ◽  
T. Lay ◽  
A. Piatanesi ◽  
M. Volpe ◽  
...  
Keyword(s):  
Coseismic Deformation ◽  
Optimal Time ◽  
Tide Gauges ◽  
First Order ◽  
Time Alignment ◽  
Finite Fault ◽  
Chile Earthquake ◽  
Tsunami Waveforms ◽  
Maule Earthquake ◽  
Seafloor Deformation

Finite-fault models for the 2010 Mw 8.8 Maule, Chile earthquake indicate bilateral rupture with large-slip patches located north and south of the epicenter. Previous studies also show that this event features significant slip in the shallow part of the megathrust, which is revealed through correction of the forward tsunami modeling scheme used in tsunami inversions. The presence of shallow slip is consistent with the coseismic seafloor deformation measured off the Maule region adjacent to the trench and confirms that tsunami observations are particularly important for constraining far-offshore slip. Here, we benchmark the method of Optimal Time Alignment (OTA) of the tsunami waveforms in the joint inversion of tsunami (DART and tide-gauges) and geodetic (GPS, InSAR, land-leveling) observations for this event. We test the application of OTA to the tsunami Green’s functions used in a previous inversion. Through a suite of synthetic tests we show that if the bias in the forward model is comprised only of delays in the tsunami signals, the OTA can correct them precisely, independently of the sensors (DART or coastal tide-gauges) and, to the first-order, of the bathymetric model used. The same suite of experiments is repeated for the real case of the 2010 Maule earthquake where, despite the results of the synthetic tests, DARTs are shown to outperform tide-gauges. This gives an indication of the relative weights to be assigned when jointly inverting the two types of data. Moreover, we show that using OTA is preferable to subjectively correcting possible time mismatch of the tsunami waveforms. The results for the source model of the Maule earthquake show that using just the first-order modeling correction introduced by OTA confirms the bilateral rupture pattern around the epicenter, and, most importantly, shifts the inferred northern patch of slip to a shallower position consistent with the slip models obtained by applying more complex physics-based corrections to the tsunami waveforms. This is confirmed by a slip model refined by inverting geodetic and tsunami data complemented with a denser distribution of GPS data nearby the source area. The models obtained with the OTA method are finally benchmarked against the observed seafloor deformation off the Maule region. We find that all of the models using the OTA well predict this offshore coseismic deformation, thus overall, this benchmarking of the OTA method can be considered successful.

scholarly journals Accounting for uncertain 3-D elastic structure in fault slip estimates

2020 ◽  
Vol 224 (2) ◽  
pp. 1404-1421
Author(s):  
Théa Ragon ◽  
Mark Simons
Keyword(s):  
Mechanical Properties ◽  
Seismic Data ◽  
Seismic Source ◽  
Sampling Procedure ◽  
Perturbation Approach ◽  
Fault Models ◽  
Bayesian Sampling ◽  
Finite Fault ◽  
Observational Errors ◽  
The Impact

SUMMARY Earthquake source estimates are affected by many types of uncertainties, deriving from observational errors, modelling choices and our simplified description of the Earth’s interior. While observational errors are often accounted for, epistemic uncertainties, which stem from our imperfect description of the forward model, are usually neglected. In particular, 3-D variations in crustal properties are rarely considered. 3-D crustal heterogeneity is known to largely affect estimates of the seismic source, using either geodetic or seismic data. Here, we use a perturbation approach to investigate, and account for, the impact of epistemic uncertainties related to 3-D variations of the mechanical properties of the crust. We validate our approach using a Bayesian sampling procedure applied to synthetic geodetic data generated from 2-D and 3-D finite-fault models. We show that accounting for uncertainties in crustal structure systematically increases the reliability of source estimates.

Variation of Source-to-Site Distance for Megathrust Subduction Earthquakes: Effects on Ground Motion Prediction Equations

2014 ◽  
Vol 30 (2) ◽  
pp. 845-866 ◽  
Author(s):  
Katsuichiro Goda ◽  
Gail M. Atkinson
Keyword(s):  
Ground Motion ◽  
Motion Prediction ◽  
Fault Models ◽  
Ground Motion Prediction Equations ◽  
Prediction Equations ◽  
Ground Motion Prediction ◽  
Motion Data ◽  
Subduction Earthquakes ◽  
Finite Fault ◽  
The Impact

This study investigates the effects of using different finite-fault source models in evaluating rupture distances for megathrust subduction earthquakes. The uncertainty of the calculated rupture distances affects interpretation of the recorded ground motions significantly. To demonstrate this from an empirical perspective, ground motion data and available finite-fault models for the 2011 M9.0 Tohoku, 2003 M8.3 Tokachi-oki, and 2005 M7.2 Miyagi-oki earthquakes are analyzed. The impact of different finite-fault models on the development of ground motion prediction equations for these large subduction events is significant. Importantly, the results suggest that comparison of observed ground motion data with existing ground motion prediction models is not straightforward; different conclusions may be reached regarding agreement/disagreement between empirical data and developed models, depending on the selected finite-fault model. These results are particularly relevant to the development of ground motion prediction equations for subduction regions.

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