Chapter 8 Northwestern Spitsbergen

1997 ◽  
Vol 17 (1) ◽  
pp. 132-153
Author(s):  
W. Brian Harland ◽  
Paul A. Doubled Ay
Keyword(s):  
Fault Zone ◽  
Central Basin ◽  
Central Province ◽  
Quaternary Sediments ◽  
The South ◽  
Large Area ◽  
Southern Boundary ◽  
James I ◽  
Western Sector ◽  
The North

Northwestern Spitsbergen is bounded by Billefjorden and Wijde-fjorden in the east and by the coastline in the north and west round to the southwest by Kongsfjorden (Fig. 8.1). The southern boundary overlaps with the Central Basin (Chapter 4) and central western sector of Spitsbergen (Chapter 9) along Kongsfjorden and Sveabreen. At this boundary Devonian and older rocks are uncon-formably overlain, and finally obscured to the south, by the cover of Carboniferous through Paleogene strata. This sector contains Andree Land, Albert I Land, Haakon VII Land, James I Land and northern Dickson Land. It is deeply penetrated by fjords and largely covered by ice.Apart from Quaternary sediments and volcanics, Cenozoic plateau lavas and the overlying platform sequence (Carboniferous through Paleogene) to the south, the main consideration here is with Devonian sediments, mid-Paleozoic migmatites and granites, and Precambrian metasediments.The Northwestern sector is bounded and divided by faults. The eastern boundary is delineated by the Billefjorden Fault Zone (BFZ) and the southwestern boundary is the postulated Kongs-fjorden-Hansbreen Fault Zone (KHFZ). These faults separate the Central Province respectively from the Eastern and Western provinces. Two main N-S oriented faults divide the sector into three terranes: the Raudfjorden Fault (RFF), and the Breibogen Fault (BBF) (Fig. 8.1) as noted by Holtedahl (1914). The three terranes are introduced below. (1) The Andree Land-Dickson Land Terrane is a large area of Devonian strata bounded by the Breibogen Fault Zone and the Billefjorden Fault Zone. (2) The Biskayerfonna-Holtedahlfonna Terrane is a N-S belt bounded to the

Observations of the Coyote Lake, California earthquake sequence of August 6, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 559-570 ◽  
Author(s):  
R. A. Uhrhammer
Keyword(s):  
San Francisco ◽  
Fault Zone ◽  
Strong Earthquake ◽  
Main Shock ◽  
B Value ◽  
Aftershock Sequence ◽  
The South ◽  
The North ◽  
Temporal And Spatial Characteristics ◽  
Largest Aftershock

abstract At 1705 UTC on August 6, 1979, a strong earthquake (ML = 5.9) occurred along the Calaveras fault zone south of Coyote Lake about 110 km southeast of San Francisco. This strong earthquake had an aftershock sequence of 31 events (2.4 ≦ ML ≦ 4.4) during August 1979. No foreshocks (ML ≧ 1.5) were observed in the 3 months prior to the main shock. The local magnitude (ML = 5.9) and the seismic moment (Mo = 6 × 1024 dyne-cm from the SH pulse) for the main shock were determined from the 100 × torsion and 3-component ultra-long period seismographs located at Berkeley. Local magnitudes are determined for the aftershocks from the maximum trace amplitudes on the Wood-Anderson torsion seismograms recorded at Berkeley (Δ ≊ 110 km). Temporal and spatial characteristics of the aftershock sequence are presented and discussed. Some key observations are: (1) the first six aftershocks (ML ≧ 2.4) proceed along the fault zone progressively to the south of the main shock; (2) all of the aftershocks (ML ≧ 2.4) to the south of the largest aftershock (ML = 4.4) have a different focal mechanism than the aftershocks to the north; (3) no aftershocks (ML ≧ 2.4) were observed significantly to the north of the main shock for the first 5 days of the sequence; and (4) the b-value (0.70 ± 0.17) for the aftershock sequence is not significantly different from the average b-value (0.88 ± 0.08) calculated for the Calaveras fault zone from 16 yr of data.

scholarly journals Volcanic centres between Frigg Fjord and Midtkap, eastern North Greenland

1981 ◽  
Vol 106 ◽  
pp. 69-75
Author(s):  
I Parsons
Keyword(s):  
Fault Zone ◽  
Fold Belt ◽  
The South ◽  
The North ◽  
Rock Types ◽  
South West ◽  
North Greenland

A series of smal! volcanic centres cut Ordovician turbidites of Formation A in the southem part of Johannes V. Jensen Land between Midtkap and Frigg Fjord (Map 2). Their general location and main rock types were described by Soper et al. (1980) and their nomenclature is adopted here for fig. 22 with the addition of the small pipe B2. A further small intrusion, south-west of Frigg Fjord, was described by Pedersen (1980). The centres lie 5-10 km south of, and parallel to, the important Harder Fjord fault zone (fig. 22) which traverses the southern part of the North Greenland fold belt and shows substantial downthrow to the south (Higgins et al., this report).

Geodynamics of the France Southeast Basin

2010 ◽  
Vol 181 (6) ◽  
pp. 477-501 ◽  
Author(s):  
Xavier Le Pichon ◽  
Claude Rangin ◽  
Youri Hamon ◽  
Nicolas Loget ◽  
Jin Ying Lin ◽  
...  
Keyword(s):  
Seismic Activity ◽  
Sedimentary Cover ◽  
Central Basin ◽  
The South ◽  
Western Basin ◽  
Active Deformation ◽  
The North ◽  
The Alps ◽  
Sediment Cover ◽  
Surrounding Areas

AbstractWe investigate the geodynamics of the Southeast Basin with the help of maps of the basement and of major sedimentary horizons based on available seismic reflection profiles and drill holes. We also present a study of the seismicity along the Middle Durance fault. The present seismic activity of the SE Basin cannot be attributed to the Africa/Eurasia shortening since spatial geodesy demonstrates that there is no significant motion of Corsica-Sardinia with respect to Eurasia and since gravitational collapse of the Alps has characterized the last few millions years. Our study demonstrates that the basement of this 140 by 200 km Triassic basin has been essentially undeformed since its formation, most probably because of the hardening of the cooling lithosphere after its 50% thinning during the Triassic distension. The regional geodynamics are thus dominated by the interaction of this rigid unit with the surrounding zones of active deformation. The 12 km thick Mesozoic sediment cover includes at its base an up to 4 km thick mostly evaporitic Triassic layer that is hot and consequently highly fluid. The sedimentary cover is thus decoupled from the basement. As a result, the sedimentary cover does not have enough strength to produce reliefs exceeding about 500 to 750 m. That the deformation and seismicity affecting the basin are the results of cover tectonics is confirmed by the fact that seismic activity in the basin only affects the sedimentary cover. Based on our mapping of the structure of the basin, we propose a simple mechanism accounting for the Neogene deformation of the sedimentary cover. The formation of the higher Alps has first resulted to the north in the shortening of the Diois-Baronnies sedimentary cover that elevated the top of Jurassic horizons by about 4 km with respect to surrounding areas to the south and west. There was thus passage from a brittle-ductile basement decollement within the higher Alps to an evaporitic decollement within the Diois-Baronnies. This shortening and consequent elevation finally induced the southward motion of the basin cover south of the Lure mountain during and after the Middle Miocene. This southward motion was absorbed by the formation of the Luberon and Trévaresse mountains to the south. To the east of the Durance fault, there is no large sediment cover. The seismicity there, is related to the absorption of the Alps collapse within the basement itself. To the west of the Salon-Cavaillon fault, on the other hand, gravity induces a NNE motion of the sedimentary cover with extension to the south and shortening to the north near Mont Ventoux. When considering the seismicity of this area, it is thus important to distinguish between the western Basin panel, west of the Salon-Cavaillon fault affected by very slow NNE gliding of the sedimentary cover, with extension to the south and shortening to the north; the central Basin panel west of the Durance fault with S gliding of the sedimentary cover and increasing shortening to the south; and finally the basement panel east of the Durance fault with intrabasement absorption of the Alps collapse through strike-slip and thrust faults.

Surface faulting along the Superstition Hills fault zone and nearby faults associated with the earthquakes of 24 November 1987

1989 ◽  
Vol 79 (2) ◽  
pp. 252-281
Author(s):  
R. V. Sharp ◽  
K. E. Budding ◽  
J. Boatwright ◽  
M. J. Ader ◽  
M. G. Bonilla ◽  
...  
Keyword(s):  
Fault Zone ◽  
Lateral Displacement ◽  
Vertical Displacement ◽  
Repeated Measurements ◽  
The South ◽  
Surface Rupture ◽  
Imperial Valley ◽  
The North ◽  
South Central ◽  
The Right

Abstract The M 6.2 Elmore Desert Ranch earthquake of 24 November 1987 was associated spatially and probably temporally with left-lateral surface rupture on many northeast-trending faults in and near the Superstition Hills in western Imperial Valley. Three curving discontinuous principal zones of rupture among these breaks extended northeastward from near the Superstition Hills fault zone as far as 9 km; the maximum observed surface slip, 12.5 cm, was on the northern of the three, the Elmore Ranch fault, at a point near the epicenter. Twelve hours after the Elmore Ranch earthquake, the M 6.6 Superstition Hills earthquake occurred near the northwest end of the right-lateral Superstition Hills fault zone. Surface rupture associated with the second event occurred along three strands of the zone, here named North and South strands of the Superstition Hills fault and the Wienert fault, for 27 km southeastward from the epicenter. In contrast to the left-lateral faulting, which remained unchanged throughout the period of investigation, the right-lateral movement on the Superstition hills fault zone continued to increase with time, a behavior that was similar to other recent historical surface ruptures on northwest-trending faults in the Imperial Valley region. We measured displacements over 339 days at as many as 296 sites along the Superstition Hills fault zone, and repeated measurements at 49 sites provided sufficient data to fit with a simple power law. Data for each of the 49 sites were used to compute longitudinal displacement profiles for 1 day and to estimate the final displacement that measured slips will approach asymptotically several years after the earthquakes. The maximum right-lateral slip at 1 day was about 50 cm near the south-central part of the North strand of Superstition Hills fault, and the predicted maximum final displacement is probably about 112 cm at Imler Road near the center of the South strand of the Superstition Hills fault. The overall distributions of right-lateral displacement at 1 day and the estimated final slip are nearly symmetrical about the midpoint of the surface rupture. The average estimated final right-lateral slip for the Superstition Hills fault zone is about 54 cm. The average left-lateral slip for the conjugate faults trending northeastward is about 23 cm. The southernmost ruptured member of the Superstition Hills fault zone, newly named the Wienert fault, extends the known length of the zone by about 4 km. The southern half of this fault, south of New River, expressed only vertical displacement on a sinuous trace. The maximum vertical slip by the end of the observation period there was about 25 cm, but its growth had not ceased. Photolineaments southeast of the end of new surface rupture suggest continuation of the Superstition Hills fault zone in farmland toward Mexico.

The Tejon Pass earthquake of October 22, 1916

1917 ◽  
Vol 7 (2) ◽  
pp. 51-60
Author(s):  
John Casper Branner
Keyword(s):  
Los Angeles ◽  
San Francisco ◽  
Fault Zone ◽  
Fault Line ◽  
The South ◽  
Epicentral Area ◽  
The North ◽  
San Andreas ◽  
North Side ◽  
To Come

Summary The area over which the shock was felt by persons at rest was 27,000 square miles or more, extending from Fresno on the north to San Diego on the south, and from Mojave to the coast. The epicenter seems to have been near the summit of the Tejon Pass, where the intensity reached VII or a little more, of the Rossi-Forel scale. At many places the shock was preceded by a pronounced roar like thunder or a high wind. Wherever the direction of the sound was noted it appeared to come from the epicentral area. The region is too thinly populated and our data are too meager to enable us to outline the area of high intensity with confidence, but the following facts seem to be fairly well established: The shock or shocks were produced by movement on the fault line that passes through the Tejon Pass and follows thence east-southeast along the axes of Leonas Valley and Anaverde Valley and northwestward through Cuddy Canyon and Cuddy Valley. The topographic evidence of the fault in the Tejon Pass is very pronounced, but there is topographic evidence of another fault that branches off from the Tejon Pass fault about a mile and a half northwest of Tejon Pass and runs east-northeast from the northwest corner of Los Angeles county, passing along the north side of Castac Lake. The depression occupied by Castac Lake seems to have been formed by a downthrow on the south side of this fault. It has been supposed that the fault through Tejon Pass was a southward prolongation of the San Andreas fault near San Francisco. The identity of these faults is far from being evident. The topography, the distribution of earthquake shocks, and the method of fracture along the fault zones all suggest a series of overlapping faults rather than one continuous fault. Mr. Hamlin says on this subject: “This fault is not a long continuous fracture, but rather a fault zone with numerous branches. Dropped blocks are not uncommon along this zone, some being a mile or more wide and twice as long.” The forms of the isoseismals of this particular earthquake, however, suggest definite relations to this fault zone.

scholarly journals 30. Fireball radiants of the 1st–15th centuries

1968 ◽  
Vol 33 ◽  
pp. 308-318 ◽  
Author(s):  
I.S. Astapović ◽  
A. K. Terenteva
Keyword(s):  
Middle Ages ◽  
Ecliptic Plane ◽  
Meteor Shower ◽  
The South ◽  
13Th Century ◽  
Large Area ◽  
Process Data ◽  
Retrograde Motion ◽  
Julian Calendar ◽  
The North

The works of E. Biot, published by the Institut National de France in 1848, made it possible to study material recorded in volumes 191 and 192 of the well-known 13th-century Encyclopaedia of Ma Touan-lin as well as records from other sources. They contain observational data of 24 centuries (especially from the 11th century) on more than 1500 fireballs, with descriptions of their positions with respect to the stars as well as descriptions of their physical, kinematic and other properties. The observation dates of the lunar calendar have been converted by Biot into dates of the Julian Calendar.We have been able to process data on 1220 fireballs. As a result of this radiants were obtained for 153 meteor showers, seven of which belong to great showers. Out of the remaining 146 radiants of the minor showers, 80 radiants are more certain than the remainder.The radiants were deduced from observations on dates recorded in short intervals from several years to several decades. First the dates of visibility were obtained along with the activity and radiants of great showers which are still active. In the Leonid shower, with retrograde motion, a shift of visibility dates to a much later period has been noted corresponding to a forward motion of the orbit's node, whereas a retrograde motion of the node is observed in the Quadrantids (i < 90°). In the Lyrids and Perseids, whose orbits are nearly perpendicular to the ecliptic plane, the nodes experienced no perturbations, and the visibility epochs for the showers remained the same during a period of 1000 years and longer. The motion of apsides resulted in a shift of the radiant; the increase of the ecliptical latitude indicated secular augmentation of the orbit's inclination (Geminids, η-Aquarids, Orionids, Leonids). The radiant of the Perseids was located in Cassiopeia, where the radiant of the present-day Cassiopeids is to be found. It appears that the Perseid stream began to cross the orbit of the Earth in 830 A.D.In the δ-Aquarids the North branch was active, while there is no evidence that the South branch had existed earlier than 900 years ago. The Virginids, Librids, Scorpionids, Sagittarids and Aurigids were quite appreciable and their studies furnish much interesting data. Particularly active were the Taurids; their North and South branches were observed over 1000 years back. The South Taurids were about half as active as the North Taurids (at present this relation is reversed). Very active were the Cygnids (July–August), which presented at that time a compact shower, now disrupted into a series of minor showers with radiants spread over a large area of the celestial sphere. Of definitive interest is the radiant of the great meteor shower observed in 1037 (August 21 by the Julian Calendar, September 9 by the Gregorian Calendar, 1950–0), α = 324°, δ = + 1°(1950–0).Some of the showers active in these early centuries are now unknown; on the other hand, some showers which are well known now were not observed in the Middle Ages. In the past millennium only those streams have survived whose orbits were so situated with respect to the orbits of the outer planets, that they were not subjected to any considerable perturbations produced by these planets.

Seismotectonics of the Ionian-Akarnania Block (IAB) and Western Greece deduced from a local seismic deployment.

2020 ◽  
Author(s):  
Antoine Haddad ◽  
Athanassios Ganas ◽  
Ioannis Kassaras ◽  
Matteo Lupi
Keyword(s):  
Fault Zone ◽  
Velocity Model ◽  
Focal Mechanisms ◽  
Seismogenic Zone ◽  
The South ◽  
S Wave ◽  
North West ◽  
The North ◽  
Short Period ◽  
Western Greece

&lt;p&gt;From July 2016 to May 2017, we deployed a local seismic network composed of 15 short-period seismic stations to investigate the ongoing seismotectonic deformation of Western Greece with emphasis on the region between Ambrakikos Gulf (to the north) and Kyparissia (to the south). The network was deployed to investigate the behavior of key crustal blocks in western Greece, such as the Ionian-Akarnania Block (IAB).&lt;/p&gt;&lt;p&gt;After applying automatic P- and S- wave phase picking we located 1200 local earthquakes using HypoInverse and constrained five 1D velocity model by applying the error minimization technique. Events were relocated using HypoDD and 76&amp;#160; focal mechanisms were computed for events with magnitudes down to M&lt;sub&gt;L&lt;/sub&gt; 2.3 using first motion polarities.&lt;/p&gt;&lt;p&gt;We combined the calculated focal mechanisms and the relocated seismicity to shed light on the IAB block boundaries. Three boundaries highlighted by previous studies were also evidenced :&lt;/p&gt;&lt;p&gt;-The north-west margin of the block, the Cephalonia Transform Fault, Europe&amp;#8216;s most active fault. NW-striking dextral strike-slip motion was recognized for this fault near the Gulf of Myrtos and the town of Fiskardo.&lt;/p&gt;&lt;p&gt;- The south-east margin is the Movri-Amaliada right-lateral Fault Zone, activated during the Movri Mt. M&lt;sub&gt;w&lt;/sub&gt; 6.4 earthquake sequence.&lt;/p&gt;&lt;p&gt;- The Ambrakikos Gulf (a young E-W rift) and the NW-striking left-lateral Katouna-Stamna Fault zone depict the north and north-eastern margins of the IAB block.&lt;/p&gt;&lt;p&gt;Seismicity lineaments and focal mechanisms define theKyllini-Cephalonia left-lateral fault, which is also highlighted by bathymetry data. We interpret this fault as the south-western margin of IAB separating an aseismic area observed between Cephalonia and Akarnania from a seismogenic zone north of Zakynthos Island and bridging NW Peloponnese with Cephalonia.&lt;/p&gt;

Research progress on the Zhongnan-Liyue Fault Zone in the South China Sea Basin

2020 ◽  
Author(s):  
Ziying Xu ◽  
Jun Wang ◽  
Hongfang Gao ◽  
Yongjian Yao
Keyword(s):  
Spatial Distribution ◽  
South China Sea ◽  
Fault Zone ◽  
South China ◽  
The South China Sea ◽  
Magnetic Data ◽  
Tectonic Deformation ◽  
The South ◽  
China Sea ◽  
The North

&lt;p&gt;We give a review of the up-to-date research situation about The Zhongnan-Liyue Fault Zone (ZLFZ), than analyze the spatial distribution and tectonic deformation feature of the ZLFZ based on the geophysical data including topographic, seismic, gravity and magnetic data. The results show that the ZLFZ has obvious north-south segmentation characteristics in in the South China Sea Basin. The north section, which is between northwest sub-basin and east sub-basin, is a narrow zone with the width of ~16 km, and is NNW trend from 18&amp;#176;N,115.5&amp;#176;E to 17.5&amp;#176;N,116&amp;#176;E. Meanwhile ,the south section, which is between southwest sub-basin and east sub-basin, is a wide zone with the width of 60-80 km, and is NNW trend from the east of ZhongshaBank to the west of LiyueBank. The main fault of the ZLFZ is NNW trend along the seamounts ridge of Zhongnan. the ZLFZ of transition region is NNE trend from the north section to the south section. According the sub-basin&amp;#8217;s sedimentary thickness and oceanic crust thickness exist obvious difference, on both sides of the ZLFZ, we speculate that the ZLFZ play an important role on geological structure of sub-basin. According to the chang of crustal structure, We speculate that the ZLFZ is at least a crustal fracture zone.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Key words: &lt;/strong&gt;South China Sea Basin; Zhongnan-Liyue Fault Zone; Spatial distribution; Tectonic deformation&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Foundation item:&lt;/strong&gt; National Natural Science Foundation of China (41606080, 41576068); The China Geological Survey Program (GZH201400202, 1212011220117, DD20160138, 1212011220116).&lt;/p&gt;

scholarly journals Nutrient regimes control phytoplankton ecophysiology in the South Atlantic

2014 ◽  
Vol 11 (2) ◽  
pp. 463-479 ◽  
Author(s):  
T. J. Browning ◽  
H. A. Bouman ◽  
C. M. Moore ◽  
C. Schlosser ◽  
G. A. Tarran ◽  
...  
Keyword(s):  
Photochemical Efficiency ◽  
South Atlantic ◽  
The South ◽  
Southern Boundary ◽  
The North ◽  
Incubation Experiments ◽  
Circumpolar Current ◽  
Control Patterns ◽  
The Antarctic ◽  
Fe Addition

Abstract. Fast Repetition Rate fluorometry (FRRf) measurements of phytoplankton photophysiology from an across-basin South Atlantic cruise (as part of the GEOTRACES programme) characterised two dominant ecophysiological regimes which were interpreted on the basis of nutrient limitation. South of the South Subtropical Convergence (SSTC) in the northern sub-Antarctic sector of the Antarctic Circumpolar Current (ACC) in the Eastern Atlantic Basin, waters are characterised by elevated chlorophyll concentrations, a dominance by larger phytoplankton cells, and low apparent photochemical efficiency (Fv / Fm). Shipboard 24 h iron (Fe) addition incubation experiments confirmed that Fe stress was primarily responsible for the low Fv / Fm, with Fe addition to these waters, either within the artificial bottle additions or naturally occurring downstream enrichment from Gough Island, significantly increasing Fv / Fm values. To the north of the SSTC at the southern boundary of the South Atlantic Gyre, phytoplankton are characterised by high values of Fv / Fm which, coupled with the low macronutrient concentrations and increased presence of picocyanobacteria, are interpreted as conditions of Fe replete, balanced macronutrient-limited growth. Spatial correlation was found between Fv / Fm and Fe:nitrate ratios, supporting the suggestion that the relative supply ratios of these two nutrients can control patterns of limitation and consequently the ecophysiology of phytoplankton in subtropical gyre and ACC regimes.

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