scholarly journals Mechanisms of the aftershocks of the Kern County, California, earthquake of 1952

1958 ◽  
Vol 48 (2) ◽  
pp. 133-146
Author(s):  
Markus Båth ◽  
Charles F. Richter
Keyword(s):  
Main Shock ◽  
Strike Slip ◽  
Kern County ◽  
The South ◽  
Longitudinal Waves ◽  
Left Hand ◽  
The North ◽  
Right Hand ◽  
First Motion ◽  
Strain Release

abstract Using directions of first motion of longitudinal waves recorded at near-by stations, the orientation of fault traces and the nature of fault motions have been deduced for fifty-seven earthquakes of the Kern County aftershock series. Unlike the main shock, the aftershocks exhibit considerable strike slip with left-hand strike slip dominating on and to the south of the White Wolf fault and right-hand strike slip and dip slip to the north of it. The two last-mentioned mechanisms represent a secondary strain release, beginning not earlier than thirty-seven hours after the main shock.

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 South Anyui suture: tectono-stratigraphy, deformations, and principal tectonic events

2009 ◽  
Vol 4 ◽  
pp. 201-221 ◽  
Author(s):  
S. D. Sokolov ◽  
G. Ye. Bondarenko ◽  
P. W. Layer ◽  
I. R. Kravchenko-Berezhnoy
Keyword(s):  
Active Continental Margin ◽  
Strike Slip ◽  
Passive Margin ◽  
The South ◽  
Asian Continent ◽  
Oblique Collision ◽  
North Asian Craton ◽  
The North ◽  
Continental Block ◽  
South Anyui Suture

Abstract. Geochronologic and structural data from the terranes of the South Anyui suture zone record a protracted deformational history before, during and after an Early Cretaceous collision of the passive margin of the Chukotka-Arctic Alaska continental block with the active continental margin of the North Asian continent. Preceding this collision, the island arc complexes of the Yarakvaam terrane on the northern margin of the North Asian craton record Early Carboniferous to Neocomian ages in ophiolite, sedimentary, and volcanic rocks. Triassic to Jurassic amphibolites constrain the timing of subduction and intraoceanic deformation along this margin. The protracted (Neocomian to Aptian) collision of the Chukotka passive margin with the North Asian continent is preserved in a range of structural styles including first north verging folding, then south verging folding, and finally late collisional dextral strike slip motions which likely record a change from orthogonal collision to oblique collision. Due to this collision, the southern passive margin of Chukotka was overthrust by tectonic nappes composed of tectono-stratigraphic complexes of the South Anyui terrane. Greenschists with ages of 115–119 Ma are related to the last stages of this collision. The postcollisional orogenic stage (Albian to Cenomanian) is characterized by sinistral strike slip faults and an extensional environment.

The arc of the Western Alps : understanding its kinematics and formation mechanisms based on new structural and paleomagnetic datas, and thermo-mechanical modelling.

2021 ◽  
Author(s):  
Quentin Brunsmann ◽  
Claudio Rosenberg ◽  
Nicolas Bellahsen ◽  
Laetitia Le Pourhiet
Keyword(s):  
Western Alps ◽  
Strike Slip ◽  
Rheological Parameters ◽  
The South ◽  
Adriatic Plate ◽  
The North ◽  
Field Evidence ◽  
Internal Zone ◽  
The Alps ◽  
East West

<p>The Alps have an overall East-West orientation, which changes radically in their western termination, where they rotate southward into a N-S strike, and then eastward into an E-W strike, forming the arc of the Western Alps. This arc is commonly inferred to have formed during collision, due to indentation of the Adriatic plate into the European continental margin. Several models attempted to provide a kinematic explanation for the formation of this arched, lateral end of the Alps. Indeed, the radial nature of the transport directions observed along the arc of the Western Alps cannot be explained by a classic convergence model.<br>For more than 50 years the formation of this arc was been associated to westward-directed indentation of Adria, accommodated along East-West oriented strike-slip faults, a sinistral one in the South of the arc and a dextral one in the North. The dextral one correspond to the Insubric Fault. The sinistral strike-slip zone, inferred to be localized along the «Stura corridor» (Piedmont, Italy) would correspond to a displacement of 100 to 150 km according to palaeogeographical, and geometric analyses. However, field evidence is scarce and barely documented in the literature.<br>Vertical axis rotations of the Adriatic indenter also inferred to be syn-collisional could have influenced the acquisition of the morphology of the arc. Paleomagnetic analyses carried out in the Internal Zone and in the Po plain suggest a southward increading amount of counter-clockwise rotation of the Adriatic plate and the Internal Zone, varying from 20°-25° in the North to nearly 120° in the South.<br>Dextral shear zones possibly accommodating this rotation in some conceptual models is observed in several places below the Penninic Front and affect the Argentera massif to the south. However, the measured displacement quantities do not appear to be equivalent to those induced by such rotations.<br>The present study aims to constrain the kinematic evolution of the arc of the Western Alps through a multidisciplinary approach. The first aspect of this project is the structural analysis of the area (Stura corridor) inferred to accommodate large sinistral displacements allowing for the westward indentation of the Adriatic indenter. We discuss the general lack of field evidence supporting sinistral strike-slip movements, in contrast to large-scale compilation of structures suggesting the possible occurrence of such displacement. The second part consists of a palaeomagnetic study, in which new data are integred with a compilation of already existing data. This compilation shows that several parts of the arc in the External Zone did not suffer any Cenozoic rotations, hence suggesting that a proto-arc already axisted at the onset collision, as suggested by independent evidence of some paleogeographic reconstruction. Finally, 2D and 3D thermo-mechanical modeling in using the pTatin3D code is used to test which structural (geometrical), and rheological parameters affected the first-order morphology of the Western Alpin arc and its kinematics. The synthesis of these different approaches allows us to propose a new model explaining the kinematics and the mechanisms of formation of the Western Alps arc.</p>

Strain partitioning around an indenter during oroclinal bending: kinematics of the Circum-Moesian fault system of the Carpatho-Balkanides

2021 ◽  
Author(s):  
Nemanja Krstekanic ◽  
Liviu Matenco ◽  
Uros Stojadinovic ◽  
Ernst Willingshofer ◽  
Marinko Toljić ◽  
...  
Keyword(s):  
Large Scale ◽  
Strike Slip ◽  
Fault System ◽  
Normal Faults ◽  
Strain Partitioning ◽  
The South ◽  
The Carpathians ◽  
The North ◽  
Moesian Platform ◽  
Parallel Extension

<p>The Carpatho-Balkanides of south-eastern Europe is a double 180° curved orogenic system. It is comprised of a foreland-convex orocline, situated in the north and east and a backarc-convex orocline situated in the south and west. The southern orocline of the Carpatho-Balkanides orogen formed during the Cretaceous closure of the Alpine Tethys Ocean and collision of the Dacia mega-unit with the Moesian Platform. Following the main orogen-building processes, the Carpathians subduction and Miocene slab retreat in the West and East Carpathians have driven the formation of the backarc-convex oroclinal bending in the south and west. The orocline formed during clockwise rotation of the Dacia mega-unit and coeval docking against the Moesian indenter. This oroclinal bending was associated with a Paleocene-Eocene orogen-parallel extension that exhumed the Danubian nappes of the South Carpathians and with a large late Oligocene – middle Miocene Circum-Moesian fault system that affected the orogenic system surrounding the Moesian Platform along its southern, western and northern margins. This fault system is composed of various segments that have different and contrasting types of kinematics, which often formed coevally, indicating a large degree of strain partitioning during oroclinal bending. It includes the curved Cerna and Timok faults that cumulate up to 100 km of dextral offset, the lower offset Sokobanja-Zvonce and Rtanj-Pirot dextral strike-slip faults, associated with orogen parallel extension that controls numerous intra-montane basins and thrusting of the western Balkans units over the Moesian Platform. We have performed a field structural study in order to understand the mechanisms of deformation transfer and strain partitioning around the Moesian indenter during oroclinal bending by focusing on kinematics and geometry of large-scale faults within the Circum-Moesian fault system.</p><p>Our structural analysis shows that the major strike-slip faults are composed of multi-strand geometries associated with significant strain partitioning within tens to hundreds of metres wide deformation zones. Kinematics of the Circum-Moesian fault system changes from transtensional in the north, where the formation of numerous basins is controlled by the Cerna or Timok faults, to strike-slip and transpression in the south, where transcurrent offsets are gradually transferred to thrusting in the Balkanides. The characteristic feature of the whole system is splaying of major faults to facilitate movements around the Moesian indenter. Splaying towards the east connects the Circum-Moesian fault system with deformation observed in the Getic Depression in front of the South Carpathians, while in the south-west the Sokobanja-Zvonce and Rtanj-Pirot faults splay off the Timok Fault. These two faults are connected by coeval E-W oriented normal faults that control several intra-montane basins and accommodate orogen-parallel extension. We infer that all these deformations are driven by the roll-back of the Carpathians slab that exerts a northward pull on the upper Dacia plate in the Serbian Carpathians. However, the variability in deformation styles is controlled by geometry of the Moesian indenter and the distance to Moesia, as the rotation and northward displacements increase gradually to the north and west.</p>

Caledonian strike-slip terrane accretion in W. Ireland: insights from very low-grade metamorphism (illite–chlorite crystallinity and b0parameter)

2009 ◽  
Vol 147 (2) ◽  
pp. 281-298 ◽  
Author(s):  
A. H. N. RICE ◽  
D. M. WILLIAMS
Keyword(s):  
High Pressure ◽  
Strike Slip ◽  
Low Grade ◽  
The South ◽  
Intermediate Pressure ◽  
The North ◽  
Show Evidence ◽  
Shelf Sediments ◽  
Terrane Accretion ◽  
Back Arc

AbstractAnalysis of pelites with detrital white-micas in the Clew Bay–Galway Bay segment of the Irish Caledonides indicates that b0data from whole-rock and < 2 μm fractions generally show differences smaller than the errors of the method, irrespective of (001) illite crystallinity values, probably due to metamorphic recrystallization. Intermediate pressure metamorphism of the Ordovician–Silurian Clew Bay Group indicates slow subduction, allowing partial thermal re-equilibration before exhumation. In contrast, the Croagh Patrick Group Laurentian shelf-sediments underwent high-pressure alteration, suggesting rapid subduction/exhumation, synchronous with strike-slip faulting. The Murrisk Group, which underwent high-intermediate pressure metamorphism in an Ordovician back-arc, forms a separate terrane to the Croagh Patrick Group to the north and also to the Ordovician Lough Nafooey and Tourmakeady groups and Rosroe Formation in the south, in which low-intermediate pressure alteration occurred. These, together with the Silurian North Galway Group, may have undergone heating due to movement over or deposition on the hot Gowlaun Detachment as the Connemara Dalradian was exhumed. The South Connemara Group also underwent a high-pressure alteration, consistent with its inferred subduction environment. Evidence of contact alteration, due to known or inferred buried late- to post-Caledonian granitoid plutons, has been found in the Clew Bay, Louisburg–Clare Island, Croagh Patrick, Murrisk and South Connemara groups. These show evidence of lower-pressure alteration than the surrounding country-rocks.

A Wall-painting at Idsworth, Hants, and a Liturgical Graffito

1945 ◽  
Vol 25 (1-2) ◽  
pp. 43-47 ◽  
Author(s):  
F. Wormald
Keyword(s):  
Fourteenth Century ◽  
Wall Painting ◽  
Left Hand ◽  
The North ◽  
Right Hand ◽  
Wild Man ◽  
North Wall ◽  
Full Consideration

On the north wall of the chancel of the small chapel at Idsworth, on the borders of Hampshire and Sussex, is a fine fourteenth-century wall-painting executed in distemper in red and yellow on a white ground. The composition is divided into two broad horizontal bands by a narrow zigzag band. In the top half is a scene with huntsmen, dogs, and a wild man, and what appears to be the arrest of St. John Baptist. In the lower part is St. John Baptist put in prison and a long scene showing Salome dancing a sword-dance before Herod and Herodias (pl. I). The scene of the huntsmen and the wild man requires rather closer examination, because it is commonly and wrongly described as showing a scene from the life of St. Hubert.On the extreme left of the picture are the remains of horsemen and dogs, then there is a figure of a crowned man winding a horn with his left hand and holding in his right hand a long bow which he rests on the ground. Behind him are two men. At his feet are dogs, and in front of him to his left are three men who bend down towards an old man covered with long hair who is emerging from some bushes on all fours. The attribution of this scene to the legend of St. Hubert requires full consideration, because an examination of the lives of that saint printed in the Acta Sanctorum yields no indication of any legend bearing the remotest resemblance to this scene. There seems, moreover, to be every indication that the whole painting represents something quite different.

scholarly journals XXIX. Conjectures on an antient Tomb in Salisbury Cathedral. By Mr. Gough

Archaeologia ◽  
1809 ◽  
Vol 2 (2) ◽  
pp. 188-193
Author(s):  
Gough
Keyword(s):  
Lower Half ◽  
The South ◽  
The West ◽  
South Side ◽  
Left Hand ◽  
Right Hand ◽  
Fourth Arch

On the south side of the nave of Salisbury cathedral, under the fourth arch from the west, lies a monument of blue speckled marble, with the figure of a bishop in pontificalibus, his right hand lifted up to give the blessing, his left hand holding the crosier. On the perpendicular sides or edge all round is cut an inscription in large capitals; and on the front of the robe, another in letters somewhat similar. The slab lay to deeply bedded in the stone foundation on which the pillars of the nave rest, that the first of these inscriptions had entirely escaped the notice of the curious, or if any had noticed it, the lower half of the letters being out of sight, rendered it unintelligible. Last summer I procured it to be raised, and the pavement disposed round it in such a manner, that it can henceforth receive no injury, but will remain the second oldest monument in that church, if the conjectures I have formed upon it are founded in truth.

scholarly journals XXIX. Conjectures on an antient Tomb in Salisbury Cathedral. By Mr. Gough

Archaeologia ◽  
1773 ◽  
Vol 2 (1) ◽  
pp. 188-193
Author(s):  
Gough
Keyword(s):  
Lower Half ◽  
The South ◽  
The West ◽  
South Side ◽  
Left Hand ◽  
Right Hand ◽  
Fourth Arch

On the south side of the nave of Salisbury cathedral, under the fourth arch from the west, lies a monument of blue speckled marble, with, the figure of a bishop in pontificalibus, his right hand lifted up to give the blessing, his left hand holding the crosier. On the perpendicular sides or edge all round is cut an inscription, in large capitals; and, on the front of the robe, another in letters somewhat similar. The slab lay to deeply bedded in the stone foundation on which the pillars of the nave reft, that the first of these inscriptions had intirely escaped the notice of the curious, or if any had noticed it, the lower half of the letters being out of sight, rendered it unintelligible. Last summer I procured it to be raised, and the pavement disposed round it in such a manner, that it can henceforth receive no injury, but will remain the second oldest monument in that church, if the conjectures I have formed upon it are founded in truth.

scholarly journals The Manix (California) earthquake of April 10, 1947*

1947 ◽  
Vol 37 (3) ◽  
pp. 171-179
Author(s):  
C. F. Richter
Keyword(s):  
Main Shock ◽  
Strike Slip ◽  
Probable Error ◽  
Origin Time ◽  
Left Hand

Summary Instrumental epicenter and origin time for the Manix earthquake are 34°58′ N, 116° 32′ W., 07:58:04 P.S.T. (15:58:04 G.C.T.), April 10, 1947. The probable error of location does not exceed a few kilometers. Certain aftershocks originated south of the main shock. Initial recorded compressions and dilatations are consistent with left-hand strike-slip on a previously identified fault which trends about N 70° E. Trace phenomena, to be reported later, were produced. Other effects, including damage, in the heavily shaken area are described.

scholarly journals TALDYK EARTHQUAKE on November 17, 2015 with KR=14.1, Mw=5.5 (Kyrgyzstan)

2021 ◽  
pp. 340-348
Author(s):  
A. Frolova ◽  
V. Grebennikova ◽  
N. Bagmanova ◽  
A. Berezina ◽  
E. Pershina ◽  
...  
Keyword(s):  
Focal Mechanism ◽  
Main Shock ◽  
Strike Slip ◽  
Complete Analysis ◽  
Depth Interval ◽  
Macroseismic Data ◽  
The South ◽  
Emergency Situations ◽  
The Third

Information on the earthquake with KR=14.1, which occurred in Kyrgyzstan on November 17, 2015, is presented. Its epicenter is related to the South Fergana zone of the Osh region, in which felt earthquakes with intensity up to I=8–9 occurred repeatedly. This event was named Taldyk according to the settlement nearest to the epicenter. The earthquake was accompanied by numerous aftershocks: for the first day, 189 events were registered, for the second – 196, for the third – 84. Most part of the aftershocks is localized within the depth interval of 12–13 km, which is practically equal to the depth of the main shock (h=13 km). The focal mechanism of the main shock has a reverse type with strike-slip components. No serious investigation of the consequences of this earthquake carried out. Some macroseismic data are received from field reports of the station operators. For a more complete analysis of the possible impact of this earthquake and, first of all, for the needs of the Ministry of Emergency Situations of Kyrgyzstan Republic, a map of theoretical isoseismals was created.

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