Optimization of the fault plane and coseismic slip from tide-gauge data for the 2nd May 2020 Ierapetra, Crete, Earthquake (Mw 6.6) and the associated tsunami

2021 ◽  
Author(s):  
Enrico Baglione ◽  
Alessandro Amato ◽  
Beatriz Brizuela ◽  
Hafize Basak Bayraktar ◽  
Stefano Lorito ◽  
...  
Keyword(s):  
Tide Gauge ◽  
Moment Tensor ◽  
A Priori ◽  
Source Parameters ◽  
Early Warning Systems ◽  
Tsunami Source ◽  
Coseismic Slip ◽  
Moment Tensors ◽  
Tsunami Early Warning ◽  
Oblique Convergence

<p>We present a tsunami source solution for the 2nd May 2020, Mw 6.6 earthquake that occurred about 80 km offshore south of Crete on the shallow portion of the Hellenic Arc Subduction Zone (HASZ). This earthquake generated a small local tsunami recorded by the Ierapetra tide gauge on Crete island's southern coast. We used these single-marigram data to constrain the main features of the causative rupture. We modelled synthetic tsunami waveforms and measured their misfits with the observed data for each set of source parameters, scanned systematically around the values constrained by some of the available moment tensors.</p><p>In the attempts to discriminate between the two auxiliary fault planes of the moment tensor solutions, our results identify a shallow highly-dipping back-thrust fault as the source of this earthquake with the lower misfit. However, a rupture on a lower angle fault, possibly a splay fault of the subduction interface, with a sinistral component due to the oblique convergence on this segment of the HASZ, cannot be ruled out.</p><p>These results are relevant in the framework of the tsunami hazard assessments and Tsunami Early Warning Systems. In these frameworks, in addition to the subduction interface and possible ruptures on splay faults, other rupture types, such as those on secondary structures of the considered subduction system, cannot be excluded a priori. This circumstance bears important consequences because, as well as splay faulting, back thrust faulting might enhance the tsunamigenic potential where the subduction itself is less tsunamigenic due to the oblique convergence.</p>

scholarly journals Characterisation of fault plane and coseismic slip for the May 2, 2020, Mw 6.6 Cretan Passage earthquake from tide-gauge tsunami data and moment tensor solutions

2021 ◽  
Author(s):  
Enrico Baglione ◽  
Stefano Lorito ◽  
Alessio Piatanesi ◽  
Fabrizio Romano ◽  
Roberto Basili ◽  
...  
Keyword(s):  
Tide Gauge ◽  
Moment Tensor ◽  
Early Warning Systems ◽  
Thrust Fault ◽  
Coseismic Slip ◽  
Moment Tensor Solution ◽  
Crete Island ◽  
Tsunami Forecasting ◽  
Oblique Convergence ◽  
Splay Fault

Abstract. We present a source solution for the tsunami generated by the Mw 6.6 earthquake that occurred on May 2, 2020, about 807thinsp;km offshore south of Crete, in the Cretan Passage, on the shallow portion of the Hellenic Arc Subduction Zone (HASZ). The tide-gauges recorded this local tsunami on the southern coast of Crete island and Kasos island. We used these tsunami observations to constrain the geometry and orientation of the causative fault, the rupture mechanism and the slip amount. We first modelled an ensemble of synthetic tsunami waveforms at the tide-gauge locations, produced for a range of earthquake parameter values as constrained by some of the available moment tensor solutions. We allow for both a splay and a back-thrust fault, corresponding to the two nodal planes of the moment tensor solution. We then measured the misfit between the synthetic and the observed marigrams for each source parameter set. Our results identify the shallow steeply-dipping back-thrust fault as the one producing the lowest misfit to the tsunami data. However, a rupture on a lower angle fault, possibly a splay fault, with a sinistral component due to the oblique convergence on this segment of the HASZ, cannot be completely ruled out. This earthquake reminds us that the uncertainty regarding potential earthquake mechanisms at a specific location remains quite significant. In this case, for example, it is not possible to anticipate if the next event will be one occurring on the subduction interface, on a splay fault, or on a back-thrust which seems the most likely for the event under investigation. This circumstance bears important consequences because back-thrust and splay faults might enhance the tsunamigenic potential with respect to the subduction interface due to their steeper dip. Then, these results are relevant for tsunami forecasting both in the framework of the long-term hazard assessment and of the early warning systems.

scholarly journals Characterization of fault plane and coseismic slip for the 2 May 2020, <i>M</i><sub>w</sub> 6.6 Cretan Passage earthquake from tide gauge tsunami data and moment tensor solutions

2021 ◽  
Vol 21 (12) ◽  
pp. 3713-3730
Author(s):  
Enrico Baglione ◽  
Stefano Lorito ◽  
Alessio Piatanesi ◽  
Fabrizio Romano ◽  
Roberto Basili ◽  
...  
Keyword(s):  
Tide Gauge ◽  
Moment Tensor ◽  
Early Warning Systems ◽  
Thrust Fault ◽  
Coseismic Slip ◽  
Moment Tensor Solution ◽  
Tsunami Observations ◽  
Tsunami Forecasting ◽  
Oblique Convergence ◽  
Splay Fault

Abstract. We present a source solution for the tsunami generated by the Mw 6.6 earthquake that occurred on 2 May 2020, about 80 km offshore south of Crete, in the Cretan Passage, on the shallow portion of the Hellenic Arc subduction zone (HASZ). The tide gauges recorded this local tsunami on the southern coast of Crete and Kasos island. We used Crete tsunami observations to constrain the geometry and orientation of the causative fault, the rupture mechanism, and the slip amount. We first modelled an ensemble of synthetic tsunami waveforms at the tide gauge locations, produced for a range of earthquake parameter values as constrained by some of the available moment tensor solutions. We allow for both a splay and a back-thrust fault, corresponding to the two nodal planes of the moment tensor solution. We then measured the misfit between the synthetic and the Ierapetra observed marigram for each source parameter set. Our results identify the shallow, steeply dipping back-thrust fault as the one producing the lowest misfit to the tsunami data. However, a rupture on a lower angle fault, possibly a splay fault, with a sinistral component due to the oblique convergence on this segment of the HASZ, cannot be completely ruled out. This earthquake reminds us that the uncertainty regarding potential earthquake mechanisms at a specific location remains quite significant. In this case, for example, it is not possible to anticipate if the next event will be one occurring on the subduction interface, on a splay fault, or on a back-thrust, which seems the most likely for the event under investigation. This circumstance bears important consequences because back-thrust and splay faults might enhance the tsunamigenic potential with respect to the subduction interface due to their steeper dip. Then, these results are relevant for tsunami forecasting in the framework of both the long-term hazard assessment and the early warning systems.

scholarly journals NEAR REAL-TIME DETERMINATION OF EARTHQUAKE SOURCE PARAMETERS FOR TSUNAMI EARLY WARNING FROM GEODETIC OBSERVATIONS

2016 ◽  
Vol XLI-B8 ◽  
pp. 117-120
Author(s):  
Sunanda Manneela ◽  
T. Srinivasa Kumar ◽  
Shailesh R. Nayak
Keyword(s):  
Real Time ◽  
Early Warning ◽  
Rapid Determination ◽  
Moment Tensor ◽  
Source Parameters ◽  
Critical Role ◽  
Tsunami Source ◽  
Tsunami Early Warning ◽  
Earthquake Source Parameters

Exemplifying the tsunami source immediately after an earthquake is the most critical component of tsunami early warning, as not every earthquake generates a tsunami. After a major under sea earthquake, it is very important to determine whether or not it has actually triggered the deadly wave. The near real-time observations from near field networks such as strong motion and Global Positioning System (GPS) allows rapid determination of fault geometry. Here we present a complete processing chain of Indian Tsunami Early Warning System (ITEWS), starting from acquisition of geodetic raw data, processing, inversion and simulating the situation as it would be at warning center during any major earthquake. We determine the earthquake moment magnitude and generate the centroid moment tensor solution using a novel approach which are the key elements for tsunami early warning. Though the well established seismic monitoring network, numerical modeling and dissemination system are currently capable to provide tsunami warnings to most of the countries in and around the Indian Ocean, the study highlights the critical role of geodetic observations in determination of tsunami source for high-quality forecasting.

scholarly journals NEAR REAL-TIME DETERMINATION OF EARTHQUAKE SOURCE PARAMETERS FOR TSUNAMI EARLY WARNING FROM GEODETIC OBSERVATIONS

2016 ◽  
Vol XLI-B8 ◽  
pp. 117-120
Author(s):  
Sunanda Manneela ◽  
T. Srinivasa Kumar ◽  
Shailesh R. Nayak
Keyword(s):  
Real Time ◽  
Early Warning ◽  
Rapid Determination ◽  
Moment Tensor ◽  
Source Parameters ◽  
Critical Role ◽  
Tsunami Source ◽  
Tsunami Early Warning ◽  
Earthquake Source Parameters

Exemplifying the tsunami source immediately after an earthquake is the most critical component of tsunami early warning, as not every earthquake generates a tsunami. After a major under sea earthquake, it is very important to determine whether or not it has actually triggered the deadly wave. The near real-time observations from near field networks such as strong motion and Global Positioning System (GPS) allows rapid determination of fault geometry. Here we present a complete processing chain of Indian Tsunami Early Warning System (ITEWS), starting from acquisition of geodetic raw data, processing, inversion and simulating the situation as it would be at warning center during any major earthquake. We determine the earthquake moment magnitude and generate the centroid moment tensor solution using a novel approach which are the key elements for tsunami early warning. Though the well established seismic monitoring network, numerical modeling and dissemination system are currently capable to provide tsunami warnings to most of the countries in and around the Indian Ocean, the study highlights the critical role of geodetic observations in determination of tsunami source for high-quality forecasting.

scholarly journals Near real-time GPS applications for tsunami early warning systems

2010 ◽  
Vol 10 (2) ◽  
pp. 181-189 ◽  
Author(s):  
C. Falck ◽  
M. Ramatschi ◽  
C. Subarya ◽  
M. Bartsch ◽  
A. Merx ◽  
...  
Keyword(s):  
Real Time ◽  
Early Warning ◽  
Early Warning System ◽  
Tide Gauge ◽  
Warning System ◽  
Early Warning Systems ◽  
Time Data ◽  
Essential Information ◽  
Tsunami Early Warning ◽  
Land Mass

Abstract. GPS (Global Positioning System) technology is widely used for positioning applications. Many of them have high requirements with respect to precision, reliability or fast product delivery, but usually not all at the same time as it is the case for early warning applications. The tasks for the GPS-based components within the GITEWS project (German Indonesian Tsunami Early Warning System, Rudloff et al., 2009) are to support the determination of sea levels (measured onshore and offshore) and to detect co-seismic land mass displacements with the lowest possible latency (design goal: first reliable results after 5 min). The completed system was designed to fulfil these tasks in near real-time, rather than for scientific research requirements. The obtained data products (movements of GPS antennas) are supporting the warning process in different ways. The measurements from GPS instruments on buoys allow the earliest possible detection or confirmation of tsunami waves on the ocean. Onshore GPS measurements are made collocated with tide gauges or seismological stations and give information about co-seismic land mass movements as recorded, e.g., during the great Sumatra-Andaman earthquake of 2004 (Subarya et al., 2006). This information is important to separate tsunami-caused sea height movements from apparent sea height changes at tide gauge locations (sensor station movement) and also as additional information about earthquakes' mechanisms, as this is an essential information to predict a tsunami (Sobolev et al., 2007). This article gives an end-to-end overview of the GITEWS GPS-component system, from the GPS sensors (GPS receiver with GPS antenna and auxiliary systems, either onshore or offshore) to the early warning centre displays. We describe how the GPS sensors have been installed, how they are operated and the methods used to collect, transfer and process the GPS data in near real-time. This includes the sensor system design, the communication system layout with real-time data streaming, the data processing strategy and the final products of the GPS-based early warning system components.

Fast acquisition of focal mechanism based on statistical analysis

2020 ◽  
Author(s):  
Marisol Monterrubio-Velasco ◽  
José Carlos Carrasco-Jimenez ◽  
Otilio Rojas ◽  
Juan Esteban Rodríguez ◽  
Josep de la Puente
Keyword(s):  
Focal Mechanism ◽  
Moment Tensor ◽  
Early Warning Systems ◽  
Spatial Dimension ◽  
Model Parameters ◽  
Data Set ◽  
Earthquake Parameters ◽  
Ground Shaking ◽  
Tsunami Early Warning ◽  
Urgent Computing

&lt;p&gt;Earthquake and tsunami early warning systems and post-event urgent computing simulations require of fast and accurate quantification of earthquake parameters such as magnitude, location and Focal Mechanism (FM). Methodologies to estimate earthquake location and magnitude are well-established and in place. However, automatic solutions of FMs are not always provided by operational institutions and are, in some cases, available only after a time-consuming inversion of the wave-forms needed to determine the moment tensor components. This precludes urgent seismic simulations, which aim at providing ground shaking maps with severe time constraints. We propose a new strategy for fast (&lt;60 s) determination of FM based on historical data sets, tested it at five different active seismic regions, Japan, New Zealand, California, Iceland, and Italy. The methodology includes the k-nearest neighbor's algorithm in a spatial dimension domain to search the most similar FMs between the data set. In our research, we focus on moderate to large earthquakes. The comparison algorithm includes the four closest events, and also a hypothetical event building by the median values of strike, dip, and rake of the k-neighbors. The validation stage includes the minimum rotated angle measure to compute the similitude between a pair of FMs. We find three model parameters, such as the minimum number of neighbors, the threshold radius that defines the neighboring sphere, and the magnitude threshold, that could improve the statistical similitude results. Our fast methodology has a 75%-90% agreement with traditional inversion mechanisms, depending on the particular tectonic region and dataset size. Our work is a key component of an urgent computing workflow, where the FM information will be used as input for ground motion simulations. Future work will assess the sensitivity of FM uncertainty in the resulting ground-shaking maps.&lt;/p&gt;

scholarly journals Tsunami Impact Prediction System Based on TsunAWI Inundation Data

2021 ◽  
Vol 15 (1) ◽  
pp. 21-40
Author(s):  
Yedi Dermadi ◽  
Yoanes Bandung
Keyword(s):  
Data Analysis ◽  
Early Warning ◽  
Tide Gauge ◽  
Early Warning Systems ◽  
Detection Algorithm ◽  
Tsunami Warning ◽  
Prediction System ◽  
Tsunami Early Warning ◽  
Impact Prediction ◽  
Short Period

It is very important for tsunami early warning systems to provide inundation predictions within a short period of time. Inundation is one of the factors that directly cause destruction and damage from tsunamis. This research proposes a tsunami impact prediction system based on inundation data analysis. The inundation data used in this analysis were obtained from the tsunami modeling called TsunAWI. The inundation data analysis refers to the coastal forecast zones for each city/regency that are currently used in the Indonesia Tsunami Early Warning System (InaTEWS). The data analysis process comprises data collection, data transformation, data analysis (through GIS analysis, predictive analysis, and simple statistical analysis), and data integration, ultimately producing a pre-calculated inundation database for inundation prediction and tsunami impact prediction. As the outcome, the tsunami impact prediction system provides estimations of the flow depth and inundation distance for each city/regency incorporated into generated tsunami warning bulletins and impact predictions based on the Integrated Tsunami Intensity Scale (ITIS-2012). In addition, the system provides automatic sea level anomaly detection from tide gauge sensors by applying a tsunami detection algorithm. Finally, the contribution of this research is expected to bring enhancements to the tsunami warning products of InaTEWS.

scholarly journals Sensitivity of the adjoint method in the inversion of tsunami source parameters

2003 ◽  
Vol 3 (5) ◽  
pp. 341-351 ◽  
Author(s):  
C. Pires ◽  
P. M. A. Miranda
Keyword(s):  
Adjoint Method ◽  
Tide Gauge ◽  
Source Parameters ◽  
Source Area ◽  
Tsunami Source ◽  
Wave Form ◽  
Observation Data ◽  
Open Domain ◽  
Direct Optimization ◽  
Fault Parameters

Abstract. This paper tests a methodology for tsunami wave-form inversion, based on the adjoint method. The method is designed to perform the direct optimization of the tsunami fault parameters, from tide-gauge data, imposing strong geophysical constrains to the inverted solutions, leading to a substantial enhancement of the signal-to-noise ratio, when compared with the classical technique based on Green’s functions of the linear long-wave model. A 4-step inversion proce-dure, which can be fully automated, consists (i) in the source area delimitation by adjoint backward ray-tracing, (ii) ad-joint optimization of the initial sea state, from a vanishing first-guess, (iii) non-linear adjustment of the fault model and (iv) final adjoint optimization in the fault parameter space. That methodology is systematically tested with four different idealized bathymetry and coastline setups (flat bathymetry in an open domain, closed conical circular lake, islands in an open domain and submarine mountains in an open domain) and different amounts of synthetic observation data, and of observational and bathymetric errors. Results show that the method works well in the presence of reasonable amounts of error and it provides, as a by-product, a resolution matrix that contains information on the inversion error, identifying the combinations of source parameters that are best and worst resolved by the inversion

Quick determination of earthquake source parameters from GPS measurements: a study of suitability for Taiwan

2019 ◽  
Vol 219 (2) ◽  
pp. 1148-1162
Author(s):  
Jiun-Ting Lin ◽  
Wu-Lung Chang ◽  
Diego Melgar ◽  
Amanda Thomas ◽  
Chi-Yu Chiu
Keyword(s):  
Rapid Determination ◽  
Moment Tensor ◽  
Near Field ◽  
Source Parameters ◽  
Early Warning Systems ◽  
Earthquake Magnitude ◽  
Observation System ◽  
Earthquake Source Parameters ◽  
Finite Fault

SUMMARY We test the feasibility of GPS-based rapid centroid moment tensor (GPS CMT) methods for Taiwan, one of the most earthquake prone areas in the world. In recent years, Taiwan has become a leading developer of seismometer-based earthquake early warning systems, which have successfully been applied to several large events. The rapid determination of earthquake magnitude and focal mechanism, important for a number of rapid response applications, including tsunami warning, is still challenging because of the limitations of near-field inertial recordings. This instrumental issue can be solved by an entirely different observation system: a GPS network. Taiwan is well posed to take advantage of GPS because in the last decade it has developed a very dense network. Thus, in this research, we explore the suitability of the GPS CMT inversion for Taiwan. We retrospectively investigate six moderate to large (Mw6.0 ∼ 7.0) earthquakes and propose a resolution test for our model, we find that the minimum resolvable earthquake magnitude of this system is ∼Mw5.5 (at 5 km depth). Our tests also suggest that the finite fault complexity, often challenging for the near-field methodology, can be ignored under such good station coverage and thus, can provide a fast and robust solution for large earthquake directly from the near field. Our findings help to understand and quantify how the proposed methodology could be implemented in real time and what its contributions could be to the overall earthquake monitoring system.

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

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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