The 29 September 2009 Samoa Islands Tsunami: Simulations Based on the First Focal Mechanism Solutions and Implications on Tsunami Early Warning Strategies

2011 ◽  
Vol 168 (6-7) ◽  
pp. 1113-1123 ◽  
Author(s):  
Roberto Tonini ◽  
Alberto Armigliato ◽  
Stefano Tinti
Keyword(s):  
Focal Mechanism ◽  
Early Warning ◽  
Tsunami Early Warning ◽  
Focal Mechanism Solutions

Rapid earthquake source characterization in the context of tsunami early warning

2021 ◽  
Author(s):  
Alberto Armigliato ◽  
Martina Zanetti ◽  
Stefano Tinti ◽  
Filippo Zaniboni ◽  
Glauco Gallotti ◽  
...  
Keyword(s):  
Focal Mechanism ◽  
Early Warning ◽  
Fault Plane ◽  
Early Warning Systems ◽  
Slip Distribution ◽  
Generation Process ◽  
Tsunami Early Warning ◽  
Earthquake Focal Mechanism ◽  
Run Up ◽  
Seismic Networks

<p>It is well known that for earthquake-generated tsunamis impacting near-field coastlines the focal mechanism, the position of the fault with respect to the coastline and the on fault slip distribution are key factors in determining the efficiency of the generation process and the distribution of the maximum run-up and inundation along the nearby coasts. The time needed to obtain the aforementioned information from the analysis of seismic records is usually too long compared to the time required to issue a timely tsunami warning/alert to the nearest coastlines. In the context of tsunami early warning systems, a big challenge is hence to be able to define 1) the relative position of the hypocenter and of the fault and 2) the earthquake focal mechanism, based only on the preliminary earthquake localization and magnitude estimation, which are made available by seismic networks soon after the earthquake occurs.</p><p>In this study, the intrinsic unpredictability of the position of the hypocenter on the fault plane is studied through a probabilistic approach based on the analysis of two finite fault model datasets (SRCMOD and USGS) and by limiting the analysis to moderate-to-large shallow earthquakes (Mw  6 and depth  50 km). After a proper homogenization procedure needed to define a common geometry for all samples in the two datasets, the hypocentral positions are fitted with different probability density functions (PDFs) separately in the along-dip and along-strike directions.</p><p>Regarding the focal mechanism determination, different approaches have been tested: the most successful is restricted to subduction-type earthquakes. It defines average values and uncertainties for strike, dip and rake angles based on a combination of a proper zonation of the main tsunamigenic subduction areas worldwide and of subduction zone geometries available from publicdatabases.</p><p>The general workflow that we propose can be schematically outlined as follows. Once an earthquake occurs and the magnitude and hypocentral solutions are made available by seismic networks, it is possible to assign the focal mechanism by selecting the characteristic values for strike, dip and rake of the zone where the hypocenter falls into. Fault length and width, as well as the slip distribution on the fault plane, are computed through regression laws against magnitude proposed by previous studies. The resulting rectangular fault plane can be discretized into a matrix of subfaults: the position of the center of each subfault can be considered as a “realization” of the hypocenter position, which can then be assigned a probability. In this way, we can define a number of earthquake fault scenarios, each of which is assigned a probability, and we can run tsunami numerical simulations for each scenario to quantify the classical observables, such as water elevation time series in selected offshore/coastal tide-gauges, flow depth, run-up, inundation distance. The final results can be provided as probabilistic distributions of the different observables.</p><p>The general approach, which is still in a proof-of-concept stage, is applied to the 16 September 2015 Illapel (Chile) tsunamigenic earthquake (Mw = 8.2). The comparison with the available tsunami observations is discussed with special attention devoted to the early-warning perspective.</p>

scholarly journals Stress relaxation arrested the mainshock rupture of the 2016 Central Tottori earthquake

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Yoshihisa Iio ◽  
Satoshi Matsumoto ◽  
Yusuke Yamashita ◽  
Shin’ichi Sakai ◽  
Kazuhide Tomisaka ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Focal Mechanism ◽  
Large Earthquake ◽  
Static Stress ◽  
Focal Mechanism Solutions ◽  
Large Earthquakes

AbstractAfter a large earthquake, many small earthquakes, called aftershocks, ensue. Additional large earthquakes typically do not occur, despite the fact that the large static stress near the edges of the fault is expected to trigger further large earthquakes at these locations. Here we analyse ~10,000 highly accurate focal mechanism solutions of aftershocks of the 2016 Mw 6.2 Central Tottori earthquake in Japan. We determine the location of the horizontal edges of the mainshock fault relative to the aftershock hypocentres, with an accuracy of approximately 200 m. We find that aftershocks rarely occur near the horizontal edges and extensions of the fault. We propose that the mainshock rupture was arrested within areas characterised by substantial stress relaxation prior to the main earthquake. This stress relaxation along fault edges could explain why mainshocks are rarely followed by further large earthquakes.

Focal mechanism solutions for roof collapse in deep mine

2015 ◽  
Vol 6 (1) ◽  
pp. 22
Author(s):  
Chun lai Wang ◽  
Hui Fu ◽  
Fu li Wang ◽  
Wei qiang Li ◽  
Ming Luo ◽  
...  
Keyword(s):  
Focal Mechanism ◽  
Deep Mine ◽  
Roof Collapse ◽  
Focal Mechanism Solutions

scholarly journals 2013 Seismic swarm recorded in Galati area, Romania: focal mechanism solutions

2016 ◽  
Vol 52 (1) ◽  
pp. 53-67 ◽  
Author(s):  
Andreea Craiu ◽  
Marius Craiu ◽  
Mihail Diaconescu ◽  
Alexandru Marmureanu
Keyword(s):  
Focal Mechanism ◽  
Focal Mechanism Solutions ◽  
Seismic Swarm

Tsunami Early Warning Within Five Minutes

2012 ◽  
Vol 170 (9-10) ◽  
pp. 1385-1395 ◽  
Author(s):  
Anthony Lomax ◽  
Alberto Michelini
Keyword(s):  
Early Warning ◽  
Tsunami Early Warning

Microseismicity and tectonics of the Nevada Seismic Zone

1971 ◽  
Vol 61 (5) ◽  
pp. 1413-1432 ◽  
Author(s):  
Frank J. Gumper ◽  
Christopher Scholz
Keyword(s):  
Sierra Nevada ◽  
Focal Mechanism ◽  
Basin And Range ◽  
Mono Lake ◽  
Tectonic Activity ◽  
Seismic Zone ◽  
Owens Valley ◽  
Western Basin ◽  
Focal Mechanism Solutions ◽  
Composite Focal Mechanism

abstract Microseismicity, composite focal-mechanism solutions, and previously-published focal parameter data are used to determine the current tectonic activity of the prominent zone of seismicity in western Nevada and eastern California, termed the Nevada Seismic Zone. The microseismicity substantially agrees with the historic seismicity and delineates a narrow, major zone of activity that extends from Owens Valley, California, north past Dixie Valley, Nevada. Focal parameters indicate that a regional pattern of NW-SE tension exists for the western Basin and Range and is now producing crustal extension within the Nevada Seismic Zone. An eastward shift of the seismic zone along the Excelsior Mountains and left-lateral strike-slip faulting determined from a composite focal mechanism indicate transform-type faulting between Mono Lake and Pilot Mountain. Based on these results and other data, it is suggested that the Nevada Seismic Zone is caused by the interaction of a westward flow of mantle material beneath the Basin and Range Province with the boundary of the Sierra Nevada batholith.

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