St. Elias, Alaska, earthquake of February 28, 1979: Tectonic setting and precursory seismic pattern

1980 ◽  
Vol 70 (5) ◽  
pp. 1595-1606
Author(s):  
Omar J. Perez ◽  
Klaus H. Jacob
Keyword(s):  
Seismic Activity ◽  
Main Shock ◽  
Tectonic Setting ◽  
Space Time ◽  
North American Plate ◽  
Rupture Zone ◽  
The North ◽  
The Pacific ◽  
Time Patterns ◽  
Large Earthquakes

abstract The St. Elias earthquake of February 28, 1979 and two earlier earthquakes in the St. Elias Range, Alaska, are shown to have involved thrust motion on gently NNW-dipping faults associated with subduction of the Pacific beneath the North American Plate. The space-time patterns of the seismicity located within and in the immediate vicinity of the rupture zone of the St. Elias event in the 16-yr period prior to it, indicate approximately 6.3 yr of relative quiescence before the main shock, interrupted by a burst of seismic activity about 3 yr prior to the event. This observed seismic pattern resembles those reported for other large earthquakes, and therefore, we suggest that the preceding burst of activity may have been a precursor.

Detections of Directional Dynamic Triggering in Intraplate Regions of the United States

2021 ◽  
Author(s):  
Vivian Tang ◽  
Kevin Chao ◽  
Suzan van der Lee
Keyword(s):  
United States ◽  
Surface Waves ◽  
Seismic Activity ◽  
Active Regions ◽  
The United States ◽  
North American Plate ◽  
Western Boundary ◽  
Eastern United States ◽  
Dynamic Triggering ◽  
The North

ABSTRACT We report tremor or local earthquake signals that occurred during the propagation of Love and Rayleigh waves from the 2012 Mw 8.6 Sumatra earthquake in three intraplate regions: Yellowstone, central Utah, and Raton basin (Colorado). These surface waves likely also dynamically triggered seismic activity along the western boundary of the North American plate, and did not trigger seismic activity in the central and eastern United States. We report additional potential dynamic triggering in the three aforementioned intraplate regions by surface waves from 37 additional large earthquakes, recorded between 2004 and 2017. These surface waves’ transient stresses generally appear to trigger tremor in seismically, volcanically, and hydrothermally active regions, such as Yellowstone, if the waves also arrive from favorable directions. These stresses do not appear to be decisive factors for triggering local earthquakes reported for the Raton basin and central Utah, whereas, surface waves’ incidence angles do appear to be important there.

scholarly journals Possibility of recovery of slip deficit rate between the North American plate and the Pacific plate off Sanriku, northeast Japan

2007 ◽  
Vol 34 (20) ◽  
Author(s):  
Shinzaburo Ozawa ◽  
Hisashi Suito ◽  
Takuya Nishimura ◽  
Mikio Tobita ◽  
Hiroshi Munekane
Keyword(s):  
North American ◽  
Pacific Plate ◽  
North American Plate ◽  
The North ◽  
Slip Deficit ◽  
The Pacific ◽  
Off Sanriku

Surface effects and tectonic setting of the 13 December 1982 North Yemen earthquake

1987 ◽  
Vol 77 (6) ◽  
pp. 2018-2037
Author(s):  
George Plafker ◽  
Robert Agar ◽  
A. H. Asker ◽  
M. Hanif
Keyword(s):  
Main Shock ◽  
Arabian Peninsula ◽  
Tectonic Setting ◽  
Tectonic Activity ◽  
Active Volcanism ◽  
The North ◽  
Surface Displacements ◽  
Southwestern Margin ◽  
Surface Manifestation ◽  
Epicentral Region

Abstract The North Yemen earthquake (Mb = 6.0) of 13 December 1982 is the first earthquake in the southern Arabian Peninsula known to be accompanied by surface displacements. The extensive destruction and loss of lives resulted entirely from widespread collapse of unreinforced masonry and mud brick structures; maximum Modified Mercalli intensity was probably VII to VIII. The only surface manifestation of tectonic activity was the occurrence of earthquake-related extensional ground cracks in the epicentral region. The cracks occur mainly in four relatively continuous north- to northwest-trending linear zones that range from a few hundred meters to 15 km in length and in irregular areas of polygonal extension cracks. The area within which the cracks occur is 22.5 km long by about 10 km wide. Continued dilation across some cracks was measured almost 1 month after the main shock. Seismicity and active volcanism in this region are inferred to reflect slow extension of the southwestern margin of the Arabia plate perpendicular to the Red Sea spreading axis.

scholarly journals Seismic rate variations prior to the 2010 Maule, Chile MW 8.8 giant megathrust earthquake

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Benoit Derode ◽  
Raúl Madariaga ◽  
Jaime Campos
Keyword(s):  
Time Scales ◽  
Seismic Activity ◽  
Main Shock ◽  
Rupture Zone ◽  
Aftershock Activity ◽  
Plate Interface ◽  
Megathrust Earthquake ◽  
Irregular Pattern ◽  
Maule Earthquake ◽  
Short Time

AbstractThe MW 8.8 Maule earthquake is the largest well-recorded megathrust earthquake reported in South America. It is known to have had very few foreshocks due to its locking degree, and a strong aftershock activity. We analyze seismic activity in the area of the 27 February 2010, MW 8.8 Maule earthquake at different time scales from 2000 to 2019. We differentiate the seismicity located inside the coseismic rupture zone of the main shock from that located in the areas surrounding the rupture zone. Using an original spatial and temporal method of seismic comparison, we find that after a period of seismic activity, the rupture zone at the plate interface experienced a long-term seismic quiescence before the main shock. Furthermore, a few days before the main shock, a set of seismic bursts of foreshocks located within the highest coseismic displacement area is observed. We show that after the main shock, the seismic rate decelerates during a period of 3 years, until reaching its initial interseismic value. We conclude that this megathrust earthquake is the consequence of various preparation stages increasing the locking degree at the plate interface and following an irregular pattern of seismic activity at large and short time scales.

scholarly journals ETAS Space–Time Modeling of Chile Triggered Seismicity Using Covariates: Some Preliminary Results

2021 ◽  
Vol 11 (19) ◽  
pp. 9143
Author(s):  
Marcello Chiodi ◽  
Orietta Nicolis ◽  
Giada Adelfio ◽  
Nicoletta D’Angelo ◽  
Alex Gonzàlez
Keyword(s):  
Time Scale ◽  
Seismic Activity ◽  
Space Time ◽  
Small Time ◽  
Etas Model ◽  
Related Data ◽  
Triggered Seismicity ◽  
The North ◽  
Time Modeling ◽  
Aftershock Sequences

Chilean seismic activity is one of the strongest in the world. As already shown in previous papers, seismic activity can be usefully described by a space–time branching process, such as the ETAS (Epidemic Type Aftershock Sequences) model, which is a semiparametric model with a large time-scale component for the background seismicity and a small time-scale component for the triggered seismicity. The use of covariates can improve the description of triggered seismicity in the ETAS model, so in this paper, we study the Chilean seismicity separately for the North and South area, using some GPS-related data observed together with ordinary catalog data. Our results show evidence that the use of some covariates can improve the fitting of the ETAS model.

Mitigating Impacts of Natural Hazards on Fishery Ecosystems

2008 ◽  
Keyword(s):  
United States ◽  
Natural Hazards ◽  
Fish Habitat ◽  
The United States ◽  
North American Plate ◽  
Fishing Communities ◽  
Plate Boundaries ◽  
Earthquake Hazards ◽  
The North ◽  
The Pacific

<em>Abstract.</em>—Fish and fishing communities are iconic symbols of Alaska. Volcanoes, earthquakes, and tsunamis also stand out as processes that define or shape the Alaska landscape. Alaska has numerous fishing ports that regularly rank in the top 10 ports for commercial landings by weight and value in the United States. In addition to commercial fisheries, subsistence fisheries and sport fishing play an important role in the economy and culture of Alaska. Alaska is home to one of the most active plate boundaries on the planet, where the Pacific Plate is subducting the North American Plate at rates greater than 5 cm/year. This process brings to Alaska earthquakes, tsunamis, and volcanic eruptions. Active plate boundaries around the Pacific basin also make Alaska vulnerable to transoceanic tsunamis generated by earthquakes thousands of miles away. Alaska is the most seismically active state in the United States by a large margin and one of the most active areas in the world. In this paper, we examine the distribution of fishing communities and fish habitat with respect to volcanic and earthquake hazards and discuss the possible implications of these natural hazards to fisheries. Because natural hazards cannot be prevented, communities must prepare for and minimize risk associated with such events. Understanding the nature and distribution of natural hazards is the first step in preparing for future events and limiting the impacts of those events.

scholarly journals Variations of VLF/LF signals observed on the ground and satellite during a seismic activity in Japan region in May–June 2008

2010 ◽  
Vol 10 (3) ◽  
pp. 529-534 ◽  
Author(s):  
A. Rozhnoi ◽  
M. Solovieva ◽  
O. Molchanov ◽  
P.-F. Biagi ◽  
M. Hayakawa ◽  
...  
Keyword(s):  
Active Region ◽  
Satellite Data ◽  
Seismic Activity ◽  
Signal Intensity ◽  
Satellite Observation ◽  
The North ◽  
North Part ◽  
The Difference ◽  
Large Earthquakes ◽  
Honshu Island

Abstract. Signals of two Japanese transmitters (22.2 kHz and 40 kHz) recorded on the ground VLF/LF station in Petropavlovsk-Kamchatsky and on board the DEMETER French satellite have been analyzed during a seismic activity in Japan in May–June 2008. The period of analysis was from 18 April to 27 June. During this time two rather large earthquakes occurred in the north part of Honshu Island – 7 May (M=6.8) and 13 June (M=6.9). The ground and satellite data were processed by a method based on the difference between the real signal in nighttime and the model one. For ground observations a clear decrease in both signals has been found several days before the first earthquake. For the second earthquake anomalies were detected only in JJI signal. The epicenters of earthquakes were in reliable reception zone of 40 kHz signal on board the DEMETER. Signal enhancement above the seismic active region and significant signal intensity depletion in the magnetically conjugate area has been found for satellite observation before the first earthquake. Anomalies in satellite data coincide in time with those in the ground-based observation.

Uplift and exhumation in Haida Gwaii driven by terrane translation and transpression along the southern Queen Charlotte fault, Canada

Geology ◽  
2020 ◽  
Vol 48 (9) ◽  
pp. 908-912
Author(s):  
Philip Schoettle-Greene ◽  
Alison R. Duvall ◽  
Ann Blythe ◽  
Eric Morley ◽  
William Matthews ◽  
...  
Keyword(s):  
North America ◽  
North American ◽  
North American Plate ◽  
Cascadia Subduction Zone ◽  
Haida Gwaii ◽  
Crustal Shortening ◽  
Basin Inversion ◽  
Subduction Initiation ◽  
The North ◽  
The Pacific

Abstract The mountainous archipelago of Haida Gwaii abuts the transpressive Pacific–North American plate margin north of the Cascadia subduction zone (northwestern North America). Topography on Haida Gwaii has been attributed to either dynamic uplift supported by subduction initiation or crustal shortening driven by shear adjacent the plate-bounding Queen Charlotte fault. In order to resolve how intraplate strain is accommodated, we obtained thermochronometry data from 20 bedrock samples on Haida Gwaii, including zircon (U-Th)/He, apatite (U-Th-Sm)/He, and apatite fission-track dates. With dates ranging from 5 to 60 Ma, we interpret exhumation rates increasing in proximity to the Queen Charlotte fault and leading to a maximum of 6 km of exhumation since 20 Ma. The onset of exhumation significantly predates the purported initiation of subduction, precluding a direct relationship between subduction initiation and the development of topography in the archipelago. Instead, exhumation onset correlates with passage of the Yakutat terrane, suggesting that North America was deformed and Haida Gwaii uplifted during terrane translation. Steady or slightly decreasing exhumation rate since the Miocene is at odds with estimated increases to intraplate convergence over this time, ruling out crustal shortening in Haida Gwaii as the only response to transpression between North America and the Pacific. From this, we conclude that plate convergence is accommodated through basin inversion and internal shortening in the North American and Pacific plates as well as potential underthrusting of the Pacific plate beneath North America.

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