Active tectonics of eastern segment of the South Wagad Fault Zone, Kachchh, Western India

2020 ◽  
Author(s):  
Abhishek Lakhote ◽  
M.G. Thakkar ◽  
Raj Sunil Kandregula ◽  
Girish Ch Kothyari ◽  
Gaurav Chauhan
Keyword(s):  
Fault Zone ◽  
Active Tectonics ◽  
Western India ◽  
The South ◽  
Eastern Segment

scholarly journals Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 102
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitrios Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Activity ◽  
Volcanic Rocks ◽  
Active Tectonics ◽  
Normal Fault ◽  
Aegean Sea ◽  
Northern Margin ◽  
The North ◽  
Eastern Aegean ◽  
Half Graben

On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.

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).

scholarly journals Slip‐rate on the Main Köpetdag (Kopeh Dagh) Strike‐slip fault, Turkmenistan, and the active tectonics of the South Caspian

Tectonics ◽  
2021 ◽  
Author(s):  
Richard Thomas Walker ◽  
Y. Bezmenov ◽  
G. Begenjev ◽  
S. Carolin ◽  
N. Dodds ◽  
...  
Keyword(s):  
Active Tectonics ◽  
Slip Rate ◽  
Strike Slip ◽  
Strike Slip Fault ◽  
The South

scholarly journals New data on the palaeo–incisions network of the south–eastern Baltic Sea

Baltica ◽  
2014 ◽  
Vol 27 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Dmitrij Gerok ◽  
Leonora Živilė Gelumbauskaitė ◽  
Tom Flodén ◽  
Algimantas Grigelis ◽  
Albertas Bitinas
Keyword(s):  
Baltic Sea ◽  
Ice Sheet ◽  
The South ◽  
The Baltic Sea ◽  
Distinctive Features ◽  
South Eastern ◽  
Fracture Systems ◽  
Present Study Area ◽  
Eastern Segment ◽  
The Baltic

The present study area is located within the south–eastern segment of the Baltic Sea framed by 55o30’–56o30’ N and 19o00’–21o15’E. The area is re-visited with the aim to describe in more detail the geologic prerequisite and development of the palaeo–incisions as well as the timing of their subsequent infillings. The channels form distinctive features in the sedimentary bedrock along the outer limits of pre–Weichselian ice sheets, on average reaching depths into the bedrock of 50 m in the nearshore zone of Lithuania to 100 m along the slope to the Gotland depression in the west. The development of palaeo–incisions systems is governed by the easily eroded late Palaeozoic to Mesozoic bedrock of the present area. Only rare ocurrences of channels have been reported from the middle and lower parts of the Palaeozoic further west in the Baltic Sea. The present investigation supports a mechanism that the channels formed below the ice near the ice sheet margin by melt water erosion under high pressure. The channels start at random where a fracture in the ice develops forming outlet of water contained below the central part of the ice sheet. The channels often merge together in the direction of the ice margin, possibly gradually adapting to previous fracture systems in the bedrock. The investigated incisions were infilled prior to the advance of the Weichselian ice sheet and some have been reopened and repeatedly infilled.

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.

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