scholarly journals Time dependent seismicity along the western coast of Canada

2016 ◽  
Vol 5 (1) ◽  
Author(s):  
Evangelos V. Christou ◽  
George Karakaisis ◽  
Emmanuel Scordilis

Decelerating generation of intermediate magnitude earthquakes (preshocks) in a narrow region (seismogenic region) and accelerating generation of relatively larger such earthquakes in a broader region (critical region) has been proposed as an appropriate model for intermediate-term earthquake prediction. We examined the seismic activity which preceded the M<sub>w</sub>=7.7 (October 28, 2012) thrust event that occurred off the west coast of Haida Gwaii, Canada (formerly the Queen Charlotte islands), by applying the decelerating-accelerating seismic strain model. We found that this mainshock was preceded by a pronounced accelerating seismic sequence with the time to the mainshock, as well as by an equally easily identifiable decelerating seismic sequence. Both precursory seismic sequences occurred in different space, time and magnitude windows. The behavior of previous mainshocks that occurred close to the 2012 earthquake was also examined by the time and magnitude predictable regional model. An attempt was also made to identify such seismic strain patterns, which may also be related to the generation of strong mainshocks along the western coast of Canada.

2021 ◽  
Vol 11 (11) ◽  
pp. 5156
Author(s):  
Abd Al-Salam Al-Masgari ◽  
Mohamed Elsaadany ◽  
Numair A. Siddiqui ◽  
Abdul Halim Abdul Latiff ◽  
Azli Abu Bakar ◽  
...  

This study identified the Pleistocene depositional succession of the group (A) (marine, estuarine, and fluvial depositional systems) of the Melor and Inas fields in the central Malay Basin from the seafloor to approximately −507 ms (522 m). During the last few years, hydrocarbon exploration in Malay Basin has moved to focus on stratigraphic traps, specifically those that existed with channel sands. These traps motivate carrying out this research to image and locate these kinds of traps. It can be difficult to determine if closely spaced-out channels and channel belts exist within several seismic sequences in map-view with proper seismic sequence geomorphic elements and stratigraphic surfaces seismic cross lines, or probably reinforce the auto-cyclic aggregational stacking of the avulsing rivers precisely. This analysis overcomes this challenge by combining well-log with three-dimensional (3D) seismic data to resolve the deposition stratigraphic discontinuities’ considerable resolution. Three-dimensional (3D) seismic volume and high-resolution two-dimensional (2D) seismic sections with several wells were utilized. A high-resolution seismic sequence stratigraphy framework of three main seismic sequences (3rd order), four Parasequences sets (4th order), and seven Parasequences (5th order) have been established. The time slice images at consecutive two-way times display single meandering channels ranging in width from 170 to 900 m. Moreover, other geomorphological elements have been perfectly imaged, elements such as interfluves, incised valleys, chute cutoff, point bars, and extinction surfaces, providing proof of rapid growth and transformation of deposits. The high-resolution 2D sections with Cosine of Phase seismic attributes have facilitated identifying the reflection terminations against the stratigraphic amplitude. Several continuous and discontinuous channels, fluvial point bars, and marine sediments through the sequence stratigraphic framework have been addressed. The whole series reveals that almost all fluvial systems lay in the valleys at each depositional sequence’s bottom bars. The degradational stacking patterns are characterized by the fluvial channels with no evidence of fluvial aggradation. Moreover, the aggradation stage is restricted to marine sedimentation incursions. The 3D description of these deposits permits distinguishing seismic facies of the abandoned mud channel and the sand point bar deposits. The continuous meandering channel, which is filled by muddy deposits, may function as horizontal muddy barriers or baffles that might isolate the reservoir body into separate storage containers. The 3rd, 4th, and 5th orders of the seismic sequences were established for the studied succession. The essential geomorphological elements have been imaged utilizing several seismic attributes.


Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 46
Author(s):  
Bachtiar W. Mutaqin ◽  
Franck Lavigne ◽  
Patrick Wassmer ◽  
Martine Trautmann ◽  
Puncak Joyontono ◽  
...  

Indonesia is exposed to earthquakes, volcanic activities, and associated tsunamis. This is particularly the case for Lombok and Sumbawa Islands in West Nusa Tenggara, where evidence of tsunamis is frequently observed in its coastal sedimentary record. If the 1815 CE Tambora eruption on Sumbawa Island generated a tsunami with well-identified traces on the surrounding islands, little is known about the consequences of the 1257 CE tremendous eruption of Samalas on the neighboring islands, and especially about the possible tsunamis generated in reason of a paucity of research on coastal sedimentary records in this area. However, on Lombok Island, the eruption of the Samalas volcano produced significant volumes of pyroclastic flows that entered the sea in the North and East of the island. These phenomena must have produced a tsunami that left their traces, especially on Sumbawa Island, whose western coastline is only 14 km away from Lombok’s eastern shore. Therefore, the main goal of this study is to investigate, find evidence, and determine the age of marine-origin sediments along the shore of the Alas Strait, Indonesia. We collected and analyzed samples of coral and seashells from marine deposits identified along the west coast of Sumbawa, i.e., in Belang Island and abandoned fishponds in Kiantar Village, in order to identify the sources and the occurrence period of these deposits events. Based on the radiocarbon dating of coral and seashell samples, we concluded that none of the identified marine deposits along the western coast of Sumbawa could be related chronologically to the 1257 CE eruption of Samalas. However, possible tsunami deposits located in Belang Island and abandoned fishponds in Kiantar Village yielded 4th century CE, 9th century CE, and 17th century CE. We also conclude that past large earthquakes triggered these tsunamis since no known volcanic eruption occurred near the Alas Strait at that time that may have triggered a tsunami.


2004 ◽  
Vol 62 (1) ◽  
pp. 105-109 ◽  
Author(s):  
Carolyn L. Ramsey ◽  
Paul A. Griffiths ◽  
Daryl W. Fedje ◽  
Rebecca J. Wigen ◽  
Quentin Mackie

Recent investigations of a limestone solution cave on the Queen Charlotte Islands (Haida Gwaii) have yielded skeletal remains of fauna including late Pleistocene and early Holocene bears, one specimen of which dates to ca. 14,400 14C yr B.P. This new fossil evidence sheds light on early postglacial environmental conditions in this archipelago, with implications for the timing of early human migration into the Americas.


Ocean Science ◽  
2011 ◽  
Vol 7 (4) ◽  
pp. 487-502 ◽  
Author(s):  
W. Callendar ◽  
J. M. Klymak ◽  
M. G. G. Foreman

Abstract. Numerical simulations of tidal flow past Cape St. James on the south tip of Haida Gwaii (Queen Charlotte Islands) are presented that indicate mesoscale dipoles are formed from coalescing tidal eddies. Observations in this region demonstrate robust eddy generation at the Cape, with the primary process being flow separation of buoyant or wind driven outflows forming large anti-cyclonic, negative potential vorticity, Haida Eddies. However, there are other times where dipoles are observed in satellites, indicating a source of positive potential vorticity must also be present. The simulations here build on previous work that implicates oscillating tidal flow past the cape in creating the positive vorticity. Small headland eddies of alternating vorticity are created each tide. During certain tidal cycles, the headland eddies coalesce and self organize in such a way as to create large >20-km diameter eddies that then self-advect into deep water. The self advection speed is faster than the beta drift of anti-cyclones, and the propagation direction appears to be more southerly than typical Haida Eddies, though the model contains no mean wind-driven flows. These eddies are smaller than Haida Eddies, but given their tidal origin, may represent a more consistent source of coastal water that is injected into the interior of the subpolar gyre.


2012 ◽  
Vol 93 (5) ◽  
pp. 1211-1229 ◽  
Author(s):  
Kenneth H. Nicholls

Near-shore benthic sediment samples collected at low tide from the western Atlantic Ocean (Sable Island, Nova Scotia, Canada) and the eastern Pacific Ocean (Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada) were searched for little-known species of the rhizarian (Cercozoa) genera Pinaciophora, Rabdiaster and other related rotosphaerids. Several representatives with complete investitures of silica-scales (the structure of which is taxonomically diagnostic) were studied by transmission and scanning electron microscopy. The validity of the genus Pinaciophora (sensu Penard, 1904) as defined by a single type of plate-scale only, was strengthened by the discovery of Pinaciophora rubicunda and of another previously undescribed entity, both of which lacked spine-scales. Several earlier reports of loose scales from marine habitats, and erroneously identified as the freshwater P. fluviatilis, might be assigned to P. marina sp. nov. The new genus Thomseniophora was erected to include all ‘Pinaciophora' previously known to produce spine-scales and seven new taxa were described. Six other little-known species of Thomseniophora, Pinaciophora and Rabdiaster were described from the Canadian west coast (Pacific Ocean) including one new species of Pinaciophora. The addition of Thomseniophora brings the number of genera assigned to the Rotosphaerida to six: Pinaciophora, Thomseniophora, Rabdiaster, Rabdiophrys and Pompholyxophrys. The presence of several apparently closely related taxa in the same collection (same location and sampling date) strengthens the conclusion that relatively small differences in the morphology of their siliceous scales were more likely caused by genetic differences than by environmental influences.


Zootaxa ◽  
2011 ◽  
Vol 2886 (1) ◽  
pp. 1 ◽  
Author(s):  
K. J. ABRAHAM ◽  
K. K. JOSHI ◽  
V. S. R. MURTY

A total of 16 species of the family Leiognathidae have been collected from the commercial landings from Cochin and Neendakara on the western coast of India from 1998–2000. Detailed morphometric data have been collected and all 16 species are redescribed with live color photographs here. Various relationships in the morphometric characteristics have been studied and regression equations fitted to enable comparison of the populations of these species from Kerala with those from other regions. Of the 16 species collected and described in the present work, five species, Nuchequula nuchalis, Equulites absconditus, Equulites leuciscus, Aurigequula longispina, and Gazza achlamys, are reported for the first time from the entire western coast of India.


2015 ◽  
Vol 14 (2) ◽  
pp. 132-141 ◽  
Author(s):  
Azimeh Karimi ◽  
Hojjatollah Saeidi

Sorghum halepensegrows in a vast range of ecological regions of Iran. In this study, inter-retrotransposon amplified polymorphism (IRAP) markers were used to assess the genetic diversity of 38 accessions ofS. halepenseand two accessions ofSorghum bicolor(used as out groups) collected from different regions of Iran. In total, 180 DNA fragments were amplified from eight combinations of IRAP primers, from which 178 (98.9%) were polymorphic. The IRAP-based trees and two-dimensional plot of principal coordinate analysis demonstrated six different groups corresponding to their geographical origin in Iranian germplasm ofS. halepense: (1) in the south-west region; (2) in the west along the Zagros Mountains; (3) in the north-west of the country; (4) in the centre of the country; (5) and (6) in the northern region along the eastern and western coast of Caspian Sea. The most variable populations were found in the centre and the west of Iran. The results showed high gene flow among different regions, although the south-western accessions were well differentiated from those growing in other regions. The accessions collected from western coast of Caspian Sea were differentiated from neighbouring regions in both morphological characters and IRAP data. The measured genetic distances were independent of geographical distances. This survey demonstrates high genetic dynamism in Iranian germplasm ofS. halepenseand indicates that the present germplasm is of great value in terms of sampling for new alleles for crop improvement.


1953 ◽  
Vol 10 (3) ◽  
pp. 125-145 ◽  
Author(s):  
G. L. Pickard ◽  
D. C. McLeod

Grand monthly means of daily observations of surface sea-water temperature and salinity from twelve light stations along the British Columbia coast during the 13 years 1935 to 1948 have been analysed. In general the temperatures reach a minimum of 45°F. ± 1° (7.2 °C. ± 0.5°) in January and February. The maximum varies from 50° to 64°F. (10° to 18 °C.) in August. The warmest waters occur in bays protected from wind action, and the coldest waters occur in regions of turbulent mixing due to wind or strong currents. The salinity along the mainland coast is a minimum in early summer, associated with the maximum run-off from melting snow. Along the west coast of Vancouver Island the minimum occurs in mid-winter, associated with maximum precipitation which is not stored as snow in this region. At the southern and northern tip of the Queen Charlotte Islands there is little or no variation of salinity because there is no land drainage of consequence in the vicinity.In passes between Georgia Strait and the sea where the waters are mixed to homogeneity by strong tidal currents the annual variation of temperature and salinity is reduced, and in some cases entirely suppressed.On the west coast of Vancouver Island it is shown that the annual cycle is affected by the dominant winds and upwelling of deep ocean waters.


1909 ◽  
Vol 6 (2) ◽  
pp. 74-75
Author(s):  
E. Douglass Isaacson

The series of beds containing graptolites in New Zealand occur in the Whakamarama district, which is situated in almost the extreme north-west of the South Island. They consist of intercalated bands of quartzite and carbonaceous argillites, with a north and south strike and dipping at a low angle to the west. As a result of the natural erosion of the land surface taking place more rapidly in the slaty layers than in the harder quartzites, the ridges and stream valleys exhibit a noticeable parallelism, those streams which enter the sea on the western coast usually taking a very sharp bend to the west, and with a somewhat gorgy channel to the sea. The valleys are for the most part densely clothed with forest trees, while the ridges of quartzite are barren, with the exception of a stunted growth of manuka (Leptospermum scoparium and L. ericoides), and in places a covering of peat to a depth of a few inches.


2013 ◽  
Vol 330 ◽  
pp. 805-810
Author(s):  
Dragos R. Rugescu

The Romanian NERVA space project, aimed at building and using a small rocket launcher for injecting nanosatellites into a LEO, requires the establishment of a secure launching area. The first candidate is on the western coast of the Black Sea and the candidate launching and flight corridor is the west-east vector above the sea. A series of ecological and safety challenges appear due to the high population density of the regions close to the sea-shores of the Black Sea; they must be catalogued and securely solved, before any space activity above the Black Sea begins. The main challenges of such an endeavor are analyzed henceforth and several solutions that fall within the scope of a recent research activity of the NERVA team are proposed.


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