Tsunami Hazard Assessment Along Chinese Coast Using Scaling Relations Developed for Tsunami Prediction

Author(s):  
Jiashen Guan ◽  
Chao An

Potential tsunamis in the western Pacific Ocean pose great threats to the Chinese coastal areas. Among all possible tsunami source regions, the Manila subduction zone draws the most attention and there have been many research works on the tsunami hazards in the South China Sea. In this study, we evaluate the tsunami hazard along the Chinese coast by investigating more potential sources, including the subduction zones of Manila, Ryukyu, Nankai, Izu–Bonin and Mariana. Two tsunami scenarios are considered for each subduction zone, a worst scenario of earthquake magnitude 9.0 and a scenario of largest earthquake magnitude known in history in this zone. Earthquake source parameters are calculated using scaling relations that have been shown to be suitable for tsunami generation. Our results show that for the Chinese coast, tsunami hazards from the Manila and Ryukyu subduction zones are severe in the worst scenarios, and tsunami hazards from the Nankai, Izu–Bonin and Mariana subduction zones are mild. Using the largest earthquake magnitude in history, tsunami hazards from all the investigated subduction zones are almost negligible. Through a sensitivity test on earthquake magnitude, we find that earthquakes of magnitude of 8.5 or larger in the Manila and Ryukyu subduction zones cause severe tsunami hazard along the Chinese coast with wave amplitude over 2 m.

2015 ◽  
Vol 15 (10) ◽  
pp. 2183-2200 ◽  
Author(s):  
R. Omira ◽  
D. Vales ◽  
C. Marreiros ◽  
F. Carrilho

Abstract. This paper is a contribution to a better understanding of the tsunamigenic potential of large submarine earthquakes. Here, we analyze the tsunamigenic potential of large earthquakes which have occurred worldwide with magnitudes around Mw = 7.0 and greater during a period of 1 year, from June 2013 to June 2014. The analysis involves earthquake model evaluation, tsunami numerical modeling, and sensors' records analysis in order to confirm the generation of a tsunami (or lack thereof) following the occurrence of an earthquake. We also investigate and discuss the sensitivity of tsunami generation to the earthquake parameters recognized to control tsunami occurrence, including the earthquake location, magnitude, focal mechanism and fault rupture depth. Through this analysis, we attempt to understand why some earthquakes trigger tsunamis and others do not, and how the earthquake source parameters are related to the potential of tsunami generation. We further discuss the performance of tsunami warning systems in detecting tsunamis and disseminating the alerts. A total of 23 events, with magnitudes ranging from Mw = 6.7 to Mw = 8.1, have been analyzed. This study shows that about 39 % of the analyzed earthquakes caused tsunamis that were recorded by different sensors with wave amplitudes varying from a few centimeters to about 2 m. Tsunami numerical modeling shows good agreement between simulated waveforms and recorded waveforms, for some events. On the other hand, simulations of tsunami generation predict that some of the events, considered as non-tsunamigenic, caused small tsunamis. We find that most generated tsunamis were caused by shallow earthquakes (depth < 30 km) and thrust faults that took place on/near the subduction zones. The results of this study can help the development of modified and improved versions of tsunami decision matrixes for various oceanic domains.


Author(s):  
Sunanda Manneela ◽  
T. Srinivasa Kumar ◽  
Shailesh R. Nayak

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.


2019 ◽  
Vol 219 (2) ◽  
pp. 1148-1162
Author(s):  
Jiun-Ting Lin ◽  
Wu-Lung Chang ◽  
Diego Melgar ◽  
Amanda Thomas ◽  
Chi-Yu Chiu

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.


2021 ◽  
Author(s):  
Hafize Başak Bayraktar ◽  
Antonio Scala ◽  
Stefano Lorito ◽  
Manuela Volpe ◽  
Carlos Sánchez Linares ◽  
...  

&lt;p&gt;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.&lt;/p&gt;&lt;p&gt;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).&lt;/p&gt;&lt;p&gt;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&amp;#237;as et al., 2016). The simulated results are validated and compared to the DART observations in the same framework considered by Davies (2019).&lt;/p&gt;


2008 ◽  
Vol 8 (4) ◽  
pp. 721-731 ◽  
Author(s):  
J. Roger ◽  
H. Hébert

Abstract. In 1856, one (or two) destructive earthquake(s) occurred off Djijelli (Algeria) and probably triggered a tsunami in the western Mediterranean Sea. Following recently published results of marine campaigns along the North-Algerian margin, a new source hypothesis for the earthquake has been proposed, and is constituted with a set of three "en échelon" fault segments positioned in agreement with previous studies of this earthquake and with macroseismic data available. The geometrical parameters for this source, in agreement with a Mw = 7.2 earthquake, display an average 40° NW dip, a 80° strike and mean dimensions of 80 km (length) × 20 km (width). A coseismic slip of 1.5 m is consistent with an average convergence rate of about 5–6 mm/yr and a recurrence period of 300–400 years. They are then introduced in the tsunami modelling code to study the propagation across the Mediterranean Sea with a special attention towards the Balearic Islands. A focus on the two major towns, Palma (Majorca) and Mahon (Minorca) Harbours shows that these places are not the most exposed (maximum water heights less than 1 m) by tsunami waves coming from this part of the African margin. Specific amplifications revealed by modelling occur off the southern coast of Minorca and the southeastern coast of Majorca, mostly related to submarine bathymetric features, and are able to produce coastal wave heights larger than 1 to 2 m as offshore Alcalfar (Minorca). A deep submarine canyon southward Minorca leads to the amplification of waves up to two times on both sides of the canyon. However these modellings could not be compared to any historical observations, non-existent for these sites. This work is a contribution to the study of tsunami hazard in western Mediterranean based on modelling, and offers a first assessment of the tsunami exposure in the Balearic Islands.


Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 372
Author(s):  
Amin Rashidi ◽  
Denys Dutykh ◽  
Zaher Hossein Shomali ◽  
Nasser Keshavarz Farajkhah ◽  
Mohammadsadegh Nouri

The uncertain tsunamigenic potential of the Makran Subduction Zone (MSZ) has made it an interesting natural laboratory for tsunami-related studies. This study aims to review the recent activities on tsunami hazard in the Makran subduction zone with a focus on deterministic and probabilistic tsunami hazard assessments. While almost all studies focused on tsunami hazard from the Makran subduction thrust, other local sources such as splay faults and landslides can be also real threats in the future. Far-field tsunami sources such as Sumatra-Andaman and Java subduction zones, commonly lumped as the Sunda subduction zone, do not seem to pose a serious risk to the Makran coastlines. The tsunamigenic potential of the western segment of the MSZ should not be underestimated considering the new evidence from geological studies and lessons from past tsunamis in the world. An overview of the results of tsunami hazard studies shows that the coastal area between Kereti to Ormara along the shoreline of Iran-Pakistan and the coastal segment between Muscat and Sur along Oman’s shoreline are the most hazardous areas. Uncertainties in studying tsunami hazard for the Makran region are large. We recommend that future studies mainly focus on the role of thick sediments, a better understanding of the plates interface geometry, the source mechanism and history of extreme-wave deposits, the contribution of other local tsunamigenic sources and vulnerability assessment for all coastlines of the whole Makran region.


2021 ◽  
pp. 875529302098802
Author(s):  
Paul Somerville

This article describes the development of scaling relations between seismic moment and rupture area of earthquakes in stable continental regions (SCRs). The article reviews the relations developed by Somerville and compares them with relations developed by other investigators. It also compares the scaling relations of SCR earthquakes with those in tectonically active continental regions (TCRs). Three different methods of estimating rupture area, based on aftershocks, slip models, and duration methods were used by Somerville to analyze the relation between seismic moment and rupture area, using earthquake source parameters compiled from published literature. For each category of data, the relations obtained were not significantly different from those obtained by constraining them to be self-similar (scale-invariant), so self-similar relations were adopted. The stress drops corresponding to these scaling relations range from 51 to 86 bars, with an average of 65 bars. This value is comparable with the value of 58 bars obtained by Leonard, and it is recommended that the Leonard scaling relations for SCR earthquakes be used for the NGA East Project. To a first approximation, the results of Somerville and those of Somerville et al. indicate that the rupture areas of SCR earthquakes are about half those of TCR earthquakes, and their stress drops are about 2.8 times higher. Allmann and Shearer find less of a difference, presumably because their intraplate category includes some earthquakes that we would assign to TCR instead of SCR. Their study indicates that the rupture areas of intraplate earthquakes are about two-thirds those of TCR earthquakes, and their stress drops are about 2 times higher.


2021 ◽  
Author(s):  
Steven J. Gibbons ◽  
Stefano Lorito ◽  
Marc de la Asunción ◽  
Manuela Volpe ◽  
Jacopo Selva ◽  
...  

&lt;p&gt;Advances in GPU-based High-Performance Computing (HPC) facilities, combined with improvements in GPU-optimized shallow water models for tsunami inundation, allow us to perform large numbers of numerical simulations of earthquake-generated tsunamis on high-resolution numerical grids. Large numbers of simulations are necessary to investigate the multi-dimensional parameter space that defines the tsunami hazard, including situations where the tsunami is generated outside major tectonic structures, where fault geometry is uncertain and can take widely different orientations. With over 1500 numerical simulations, we perform suites of systematic parameter searches to investigate the sensitivity of inundation at the towns of Catania and Siracusa on Sicily to changes both in the earthquake source parameters and in the specification of the Manning friction coefficient. The inundation is modelled using the GPU-based Tsunami-HySEA code on a system of nested topo-bathymetric grids with a finest spatial resolution of 10 meters. We consider tsunamigenesis by large earthquakes with uniform slip where the location, focal depth, fault dimensions and slip, together with the angles of strike, dip, and rake, are defined by the standard Okada parameters. We consider sources both close to the shore, in which significant co-seismic deformation occurs, and offshore, where co-seismic deformation is negligible. For the offshore earthquake sources, we see systematic and intuitive changes in the inundation with changes in strike, dip, rake, and depth. For the near-shore sources, the dependency is far more complicated and co-seismic deformation becomes significant in determining the inundation. The sensitivity studies provide clear guidelines as to the necessary resolution for source discretization for Probabilistic Tsunami Hazard Analysis, with a need for a far finer discretization of local sources than for more distant sources. For a small number of earthquake sources, we study systematically the inundation as a function of the Manning Friction Coefficient. The sensitivity of the inundation to this parameter varies greatly for different earthquake sources and topo-bathymetry at the coastline of interest. An understanding of all these dependencies is needed to better understand the consequences of tsunamigenic earthquake models with more complex geometries, and in quantifying the epistemic uncertainty in the tsunami hazard.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;This work is partially funded by the European Union&amp;#8217;s Horizon 2020 Research and Innovation Program under grant agreement No 823844 (ChEESE Center of Excellence, www.cheese-coe.eu). Computational resources made available through Sigma2/UNINETT on Saga at NTNU, Trondheim, Norway (in project nn5008k) and through PRACE on Marconi-100 at CINECA, Rome, Italy (through PRACE grant Pra21_5386/TsuHazAP).&lt;/p&gt;


Author(s):  
Sunanda Manneela ◽  
T. Srinivasa Kumar ◽  
Shailesh R. Nayak

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.


2021 ◽  
Vol 5 (2) ◽  
pp. 113-127
Author(s):  
A.S. Prytkov ◽  
◽  
N.F. Vasilenko ◽  

The strong earthquake with moment magnitude Mw = 7.5 occurred on March 25, 2020, in the North Kurils to the southeast of the Paramushir Island. The hypocenter of the earthquake was located under the oceanic rise of deep-sea trench in the subducting Pacific lithospheric plate. This earthquake has been the strongest seismic event since 1900 for an area about 800 km long of the outer rise of the trench. It also was the strongest earthquake for the 300-kilometer long area of the Kuril-Kamchatka subduction zone adjacent to the epicenter. The article summarizes the data on the Paramushir earthquake. Tectonic position of the earthquake, source parameters, features of the aftershock process development, as well as coseismic displacement of the nearest continuous GNSS station are considered. The performed analysis did not allow us to clearly determine the rupture plane in the source. Nevertheless, the study of the features of the outer-rise earthquake is a matter of scientific interest, since the stress state of the bending area of the subducting Pacific lithospheric plate reflects the interplate interaction in the subduction zone.


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