scholarly journals Large submarine earthquakes that occurred worldwide in a 1-year period (June 2013 to June 2014) – a contribution to the understanding of tsunamigenic potential

2015 ◽  
Vol 15 (10) ◽  
pp. 2183-2200 ◽  
Author(s):  
R. Omira ◽  
D. Vales ◽  
C. Marreiros ◽  
F. Carrilho
Keyword(s):  
Numerical Modeling ◽  
Subduction Zones ◽  
Source Parameters ◽  
Tsunami Generation ◽  
Earthquake Parameters ◽  
Shallow Earthquakes ◽  
Earthquake Source Parameters ◽  
Tsunami Numerical Modeling ◽  
Submarine Earthquakes ◽  
Earthquake Model

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.

scholarly journals Large submarine earthquakes occurred worldwide, 1 year period (June 2013 to June 2014), – contribution to the understanding of tsunamigenic potential

2015 ◽  
Vol 3 (3) ◽  
pp. 1861-1887
Author(s):  
R. Omira ◽  
D. Vales ◽  
C. Marreiros ◽  
F. Carrilho
Keyword(s):  
Focal Mechanism ◽  
Near Field ◽  
Normal Faults ◽  
Tsunami Generation ◽  
Earthquake Parameters ◽  
Earthquake Hypocenter ◽  
Earthquake Focal Mechanism ◽  
Tsunami Numerical Modeling ◽  
Submarine Earthquakes ◽  
Earthquake Model

Abstract. This paper is a contribution to a better understanding of tsunamigenic potential from large submarine earthquakes. Here, we analyse the tsunamigenic potential of large earthquakes 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 modelling, and sensors' records analysis in order to confirm the generation or not of a tsunami following the occurrence of an earthquake. We also investigate and discuss the sensitivity of tsunami generation to the earthquake parameters recognized to control the tsunami occurrence, including the earthquake magnitude, focal mechanism and fault rupture depth. A total of 23 events, with magnitudes ranging from Mw 6.7 to Mw 8.1 and hypocenter depths varying from 10 up to 585 km, have been analyzed in this study. Among them, 52% are thrust faults, 35% are strike-slip faults, and 13% are normal faults. Most analyzed events have been occurred in the Pacific Ocean. This study shows that about 39% of the analyzed earthquakes caused tsunamis that were recorded by different sensors with wave amplitudes varying from few centimetres to about 2 m. Some of them caused inundations of low-lying coastal areas and significant damages in harbours. On the other hand, tsunami numerical modeling shows that some of the events, considered as non-tsunamigenic, might trigger small tsunamis that were not recorded due to the absence of sensors in the near-field areas. We also find that the tsunami generation is mainly dependent of the earthquake focal mechanism and other parameters such as the earthquake hypocenter depth and the magnitude. The results of this study can help on the compilation of tsunami catalogs.

scholarly journals The use of parallel computing for the high-resolution determination of earthquake source parameters

2019 ◽  
pp. 68-75
Author(s):  
A. S. Fomochkina ◽  
V. G. Bukchin
Keyword(s):  
Parallel Computing ◽  
Focal Mechanism ◽  
Source Parameters ◽  
Nodal Plane ◽  
Earthquake Parameters ◽  
Earthquake Source Parameters ◽  
Detailed Search ◽  
High Degree ◽  
Special Case

Alongside the determination of the focal mechanism and source depth of an earthquake by direct examination of their probable values on a grid in the parameter space, also the resolution of these determinations can be estimated. However, this approach requires considerable time in the case of a detailed search. A special case of a shallow earthquake whose one nodal plane is subhorizontal is an example of the sources that require the use of a detailed grid. For studying these events based on the records of the long-period surface waves, the grids with high degree of detail in the angles of the focal mechanism are required. We discuss the application of the methods of parallel computing for speeding up the calculations of earthquake parameters and present the results of studying the strongest aftershock of the Tohoku, Japan, earthquake by this approach.

National Seismological Network in India for Real-Time Earthquake Monitoring

2021 ◽  
Author(s):  
Brijesh K. Bansal ◽  
Ajeet P. Pandey ◽  
Ajay P. Singh ◽  
Gaddale Suresh ◽  
Ravi K. Singh ◽  
...  
Keyword(s):  
Real Time ◽  
Source Parameters ◽  
Focal Depth ◽  
Streaming Data ◽  
Small Aperture ◽  
Earthquake Parameters ◽  
Seismic Stations ◽  
National Network ◽  
Earthquake Source Parameters ◽  
Seismological Network

Abstract The National Seismological Network (NSN) of India has a history of more than 120 yr. During the last two decades, the NSN has gone through a significant modernization process, involving installation of seismic stations equipped with a broadband seismograph (BBS) and a strong-motion accelerograph (SMA). Each station has a very-small-aperture terminal connectivity for streaming data in real time to the central receiving station (CRS) in New Delhi. Seismic data recorded by the network are analyzed continuously on 24×7 basis to monitor the earthquakes in India and its adjoining regions. In this article, we present details of BBS and SMA network configurations; data streaming from the field seismic stations to the CRS for analysis; and the automatic and manual publication of the earthquake parameters including location coordinates, focal depth, time of occurrence, and magnitude, etc. Details of historically significant analog seismic charts and the seismic catalog, which includes more than 34,000 events with magnitude Mw 1.7–9.3 since 1505, are provided. The national network of India has been strengthened over the years and is now capable of estimating the main earthquake source parameters within ∼5–10min with an average of about 8.0 min. The spatial analysis of minimum magnitude of completeness further indicates a significant enhancement in minimum threshold magnitude detection capability of the network in recent decades.

scholarly journals Appraising the Early-est earthquake monitoring system for tsunami alerting at the Italian Candidate Tsunami Service Provider

2015 ◽  
Vol 15 (9) ◽  
pp. 2019-2036 ◽  
Author(s):  
F. Bernardi ◽  
A. Lomax ◽  
A. Michelini ◽  
V. Lauciani ◽  
A. Piatanesi ◽  
...  
Keyword(s):  
Service Provider ◽  
Epicentral Distance ◽  
Source Parameters ◽  
Earthquake Source ◽  
Tsunami Warning ◽  
Earthquake Parameters ◽  
Warning Messages ◽  
Earthquake Source Parameters ◽  
Hypocenter Depth ◽  
Epicenter Location

Abstract. In this paper we present and discuss the performance of the procedure for earthquake location and characterization implemented in the Italian Candidate Tsunami Service Provider at the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome. Following the ICG/NEAMTWS guidelines, the first tsunami warning messages are based only on seismic information, i.e., epicenter location, hypocenter depth, and magnitude, which are automatically computed by the software Early-est. Early-est is a package for rapid location and seismic/tsunamigenic characterization of earthquakes. The Early-est software package operates using offline-event or continuous-real-time seismic waveform data to perform trace processing and picking, and, at a regular report interval, phase association, event detection, hypocenter location, and event characterization. Early-est also provides mb, Mwp, and Mwpd magnitude estimations. mb magnitudes are preferred for events with Mwp &amp;lesssim; 5.8, while Mwpd estimations are valid for events with Mwp &amp;gtrsim; 7.2. In this paper we present the earthquake parameters computed by Early-est between the beginning of March 2012 and the end of December 2014 on a global scale for events with magnitude M &amp;geq; 5.5, and we also present the detection timeline. We compare the earthquake parameters automatically computed by Early-est with the same parameters listed in reference catalogs. Such reference catalogs are manually revised/verified by scientists. The goal of this work is to test the accuracy and reliability of the fully automatic locations provided by Early-est. In our analysis, the epicenter location, hypocenter depth and magnitude parameters do not differ significantly from the values in the reference catalogs. Both mb and Mwp magnitudes show differences to the reference catalogs. We thus derived correction functions in order to minimize the differences and correct biases between our values and the ones from the reference catalogs. Correction of the Mwp distance dependency is particularly relevant, since this magnitude refers to the larger and probably tsunamigenic earthquakes. Mwp values at stations with epicentral distance Δ &amp;lesssim; 30° are significantly overestimated with respect to the CMT-global solutions, whereas Mwp values at stations with epicentral distance Δ &amp;gtrsim; 90° are slightly underestimated. After applying such distance correction the Mwp provided by Early-est differs from CMT-global catalog values of about δ Mwp &amp;approx; 0.0 &amp;mp; 0.2. Early-est continuously acquires time-series data and updates the earthquake source parameters. Our analysis shows that the epicenter coordinates and the magnitude values converge within less than 10 min (5 min in the Mediterranean region) toward the stable values. Our analysis shows that we can compute Mwp magnitudes that do not display short epicentral distance dependency overestimation, and we can provide robust and reliable earthquake source parameters to compile tsunami warning messages within less than 15 min after the event origin time.

scholarly journals Appraising the Early-est earthquake monitoring system for tsunami alerting at the Italian candidate Tsunami Service Provider

2015 ◽  
Vol 3 (4) ◽  
pp. 2913-2952 ◽  
Author(s):  
F. Bernardi ◽  
A. Lomax ◽  
A. Michelini ◽  
V. Lauciani ◽  
A. Piatanesi ◽  
...  
Keyword(s):  
Service Provider ◽  
Epicentral Distance ◽  
Source Parameters ◽  
Earthquake Source ◽  
Tsunami Warning ◽  
Earthquake Parameters ◽  
Earthquake Source Parameters ◽  
Hypocenter Depth ◽  
Epicenter Location ◽  
Distance Correction

Abstract. In this paper we present the procedure for earthquake location and characterization implemented in the Italian candidate Tsunami Service Provider at INGV in Roma. Following the ICG/NEAMTWS guidelines, the first tsunami warning messages are based only on seismic information, i.e. epicenter location, hypocenter depth and magnitude, which are automatically computed by the software Early-est. Early-est is a package for rapid location and seismic/tsunamigenic characterization of earthquakes. The Early-est software package operates on offline-event or continuous-realtime seismic waveform data to perform trace processing and picking, and, at a regular report interval, phase association, event detection, hypocenter location, and event characterization. In this paper we present the earthquake parameters computed by Early-est from the beginning of 2012 till the end of December 2014 at global scale for events with magnitude M &amp;geq; 5.5, and the detection timeline. The earthquake parameters computed automatically by Early-est are compared with reference manually revised/verified catalogs. From our analysis the epicenter location and hypocenter depth parameters do not differ significantly from the values in the reference catalogs. The epicenter coordinates generally differ less than 20 &amp;mp; 20 km from the reference epicenter coordinates; focal depths are less well constrained and differ generally less than 0 &amp;mp; 30 km. Early-est also provides mb, Mwp and Mwpd magnitude estimations. mb magnitudes are preferred for events with Mwp &amp;lesssim; 5.8, while Mwpd are valid for events with Mwp &amp;gtrsim; 7.2. The magnitude mb show wide differences with respect to the reference catalogs, we thus apply a linear correction mbcorr = mb · 0.52 + 2.46, such correction results into δmb ≈ 0.0 &amp;mp; 0.2 uncertainty with respect the reference catalogs. As expected the Mwp show distance dependency. Mwp values at stations with epicentral distance Δ &amp;lesssim; 30° are significantly overestimated with respect the CMT-global solutions, whereas Mwp values at stations with epicentral distance Δ &amp;gtrsim; 90° are slightly underestimated. We thus apply a 3rd degree polynomial distance correction. After applying the distance correction, the Mwp provided by Early-est differs from CMT-global catalog values of about δ Mwp ≈ 0.0 &amp;mp; 0.2. Early-est continuously acquires time series data and updates the earthquake source parameters. Our analysis shows that the epicenter coordinates and the magnitude values converge rather quickly toward the final values. Generally we can provide robust and reliable earthquake source parameters to compile tsunami warning message within less than about 15 min after event origin time.

Estimation of the Parameters of Historical Earthquakes with a New Attenuation Equation in Yunnan Province, China

2020 ◽  
Vol 91 (5) ◽  
pp. 2651-2661 ◽  
Author(s):  
Guoliang Lin ◽  
Jian Wang
Keyword(s):  
Yunnan Province ◽  
Hazard Analysis ◽  
Source Parameters ◽  
Historical Earthquakes ◽  
Intensity Data ◽  
Earthquake Parameters ◽  
Intensity Attenuation ◽  
Earthquake Source Parameters ◽  
Data Points ◽  
Optimal Intensity

Abstract Yunnan Province is in southwest China, where the seismicity has been active since ancient times. Generally, the uncertainty of historical earthquake parameters is larger. To amend the parameters of historical earthquakes, we have developed a new intensity attenuation equation. From 2000 to 2018, there were 25 instrumentally recorded earthquakes with Ms 5.0–6.6 in Yunnan. The parameters of those earthquake events, including their epicentral locations and magnitudes, are determined with high accuracy. Meanwhile, total intensity values of 1345 intensity data points have been carefully assessed by survey. With both accurate earthquake parameters and valuable intensity data, a new intensity attenuation equation has been established. The result shows the optimal intensity magnitude MI can be calculated from the mean of Mi=(I−2.1113+0.0412Δi+1.3717lgΔi)/1.1641, in which Δi is the distance between the epicenter and the surveyed seismic point. By adapting the method proposed by Bakun and Wentworth (1997) for determining earthquake source parameters directly from historical intensity data, we have tested retrospectively the new attenuation on the 25 instrumentally recorded earthquakes. Then this attenuation was applied to deal with the parameters of two historical earthquakes, the 26 February 1713 Xundian earthquake and the 11 May 1909 Huaning earthquakes. Our results reduced the uncertainty of previously estimated parameters, which were large. The amended parameters will be valuable for seismic hazard analysis and earthquake disaster reduction.

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

2021 ◽  
Author(s):  
Jiashen Guan ◽  
Chao An
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Source Parameters ◽  
Earthquake Magnitude ◽  
Tsunami Hazard ◽  
Tsunami Source ◽  
Scaling Relations ◽  
Tsunami Hazards ◽  
Earthquake Source Parameters ◽  
Chinese Coast

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.

Waveform tomography in the Mediterranean and Southeast Asia

2020 ◽  
Author(s):  
Nienke Blom ◽  
Andreas Fichtner ◽  
Alexey Gokhberg ◽  
Nicholas Rawlinson ◽  
Deborah Wehner
Keyword(s):  
Southeast Asia ◽  
Subduction Zones ◽  
Deep Structure ◽  
Source Parameters ◽  
Seismic Inversion ◽  
Earthquake Source Parameters ◽  
North Borneo ◽  
The World ◽  
The Mediterranean ◽  
Waveform Tomography

&lt;p&gt;In this work, we present results from waveform tomography conducted in the Mediterranean and Southeast Asia. Whilst computationally more expensive than ray-based imaging methods, the advantage of waveform methods lies in their ability to incorporate in a consistent manner all the information contained in seismograms &amp;#8211; not just the arrivals of certain, specified phases. We can therefore naturally and coherently exploit body and multimode surface waves, and take into account source effects, frequency-dependence, wavefront healing, anisotropy and attenuation.&lt;/p&gt;&lt;p&gt;Here, we look at applications of this method in two geologically complex regions: the Mediterranean and Southeast Asia. Both are characterised by broadscale convergence and a complicated pattern of interactions between larger and smaller-scale tectonic plates.&lt;/p&gt;&lt;p&gt;The Mediterranean is historically one of the best studied areas in the world, with an impressive density of seismic stations which greatly aids the detailed imaging of the region. We have been able to image the Central and Eastern Mediterranean down to the mantle transition zone, thereby illuminating the complex slab structures and geometries within the domain. We identify several main slabs that correspond to major current and former subduction zones.&lt;/p&gt;&lt;p&gt;In Southeast Asia, we work at a larger scale, with a model domain encompassing the Sunda arc (which gives rise to some of the world&amp;#8217;s most significant natural hazards), the Banda arc with its spectacular 180&amp;#176; curvature and various smaller-scale features, such as the tectonically complex island of Sulawesi. To date, sparse instrument coverage in the region has led to a heterogeneous path coverage, in particular around Borneo which is located in an intra-plate setting. A recent series of temporary seismometer deployments in Sabah (North Borneo), Kalimantan, Sulawesi and the Celebes Sea allows us to fill the gaps in the publicly available data, thereby providing new opportunities to investigate the region's complexity using waveform tomography.&lt;/p&gt;&lt;p&gt;In this presentation, we will also discuss a number of features and &amp;#8220;best practices&amp;#8221; that can significantly influence waveform tomography results. In particular, we highlight how we can optimise sensitivity to deep structure by combining long-period data with a window selection approach that specifically targets body wave signals, and we discuss the effect of uncertainties in earthquake source parameters on the seismic inversion process.&lt;/p&gt;

scholarly journals Fully probabilistic seismic source inversion – Part 1: Efficient parameterisation

2013 ◽  
Vol 5 (2) ◽  
pp. 1125-1162 ◽  
Author(s):  
S. C. Stähler ◽  
K. Sigloch
Keyword(s):  
Moment Tensor ◽  
Source Parameters ◽  
Practical Importance ◽  
Principal Component ◽  
Seismic Source ◽  
Empirical Orthogonal Functions ◽  
Time Function ◽  
Source Inversion ◽  
Source Time Function ◽  
Earthquake Parameters

Abstract. Seismic source inversion is a non-linear problem in seismology where not just the earthquake parameters themselves, but also estimates of their uncertainties are of great practical importance. Probabilistic source inversion (Bayesian inference) is very adapted to this challenge, provided that the parameter space can be chosen small enough to make Bayesian sampling computationally feasible. We propose a framework for PRobabilistic Inference of Source Mechanisms (PRISM) that parameterises and samples earthquake depth, moment tensor, and source time function efficiently by using information from previous non-Bayesian inversions. The source time function is expressed as a weighted sum of a small number of empirical orthogonal functions, which were derived from a catalogue of >1000 STFs by a principal component analysis. We use a likelihood model based on the cross-correlation misfit between observed and predicted waveforms. The resulting ensemble of solutions provides full uncertainty and covariance information for the source parameters, and permits to propagate these source uncertainties into travel time estimates used for seismic tomography. The computational effort is such that routine, global estimation of earthquake mechanisms and source time functions from teleseismic broadband waveforms is feasible.

Strain to Ground Motion Conversion of DAS Data for Earthquake Magnitude and Stress Drop Determination

2021 ◽  
Author(s):  
Itzhak Lior ◽  
Anthony Sladen ◽  
Diego Mercerat ◽  
Jean-Paul Ampuero ◽  
Diane Rivet ◽  
...  
Keyword(s):  
Early Warning ◽  
Stress Drop ◽  
Source Parameters ◽  
Simulated Data ◽  
Earthquake Early Warning ◽  
Body Waves ◽  
Ocean Bottom ◽  
Correlated Noise ◽  
S Wave ◽  
Earthquake Source Parameters

&lt;p&gt;The use of Distributed Acoustic Sensing (DAS) presents unique advantages for earthquake monitoring compared with standard seismic networks: spatially dense measurements adapted for harsh environments and designed for remote operation. However, the ability to determine earthquake source parameters using DAS is yet to be fully established. In particular, resolving the magnitude and stress drop, is a fundamental objective for seismic monitoring and earthquake early warning. To apply existing methods for source parameter estimation to DAS signals, they must first be converted from strain to ground motions. This conversion can be achieved using the waves&amp;#8217; apparent phase velocity, which varies for different seismic phases ranging from fast body-waves to slow surface- and scattered-waves. To facilitate this conversion and improve its reliability, an algorithm for slowness determination is presented, based on the local slant-stack transform. This approach yields a unique slowness value at each time instance of a DAS time-series. The ability to convert strain-rate signals to ground accelerations is validated using simulated data and applied to several earthquakes recorded by dark fibers of three ocean-bottom telecommunication cables in the Mediterranean Sea. The conversion emphasizes fast body-waves compared to slow scattered-waves and ambient noise, and is robust even in the presence of correlated noise and varying wave propagation directions. Good agreement is found between source parameters determined using converted DAS waveforms and on-land seismometers for both P- and S-wave records. The demonstrated ability to resolve source parameters using P-waves on horizontal ocean-bottom fibers is key for the implementation of DAS based earthquake early warning, which will significantly improve hazard mitigation capabilities for offshore and tsunami earthquakes.&lt;/p&gt;

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