The Whittier Narrows, California Earthquake of October 1, 1987—Seismology

1988 ◽  
Vol 4 (1) ◽  
pp. 43-53 ◽  
Author(s):  
L. Jones ◽  
E. Hauksson
Keyword(s):  
Los Angeles ◽  
Los Angeles Basin ◽  
The West ◽  
Northern Margin ◽  
The North ◽  
Rupture Area ◽  
Largest Aftershock ◽  
Large Earthquakes ◽  
East West ◽  
Strike Slip Movement

The October 1, 1987 Whittier Narrows earthquake ( ML = 5.9) was located at 34° 3.0′N, 118° 4.8′W, at the northwestern end of the Puente Hills. The sequence ruptured a small part, 4 km by 5 km, of a previously unidentified, buried, thrust fault that strikes east-west and dips 25° down to the north. This fault may be part of a large system of thrust faults extending across the entire east-west length of the northern margin of the Los Angeles basin. The focus of the mainshock is deep, at 14 ± 1 km. The largest aftershock ( ML = 5.3) produced mostly strike-slip movement on a steeply dipping, northwest plane, that bounds the mainshock rupture area to the west. Enhancement of the Los Angeles basin seismic network would facilitate investigation of the potential of these faults for moderate-sized or large earthquakes.

scholarly journals Evidence of Unknown Paleo-Tsunami Events along the Alas Strait, West Sumbawa, Indonesia

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 46
Author(s):  
Bachtiar W. Mutaqin ◽  
Franck Lavigne ◽  
Patrick Wassmer ◽  
Martine Trautmann ◽  
Puncak Joyontono ◽  
...  
Keyword(s):  
Radiocarbon Dating ◽  
Pyroclastic Flows ◽  
Western Coast ◽  
Eastern Shore ◽  
Tsunami Deposits ◽  
The West ◽  
Marine Deposits ◽  
Sedimentary Records ◽  
The North ◽  
Large Earthquakes

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.

2019 Ridgecrest Earthquake Reveals Areas of Los Angeles That Amplify Shaking of High-Rises

2020 ◽  
Vol 91 (6) ◽  
pp. 3370-3380
Author(s):  
Monica D. Kohler ◽  
Filippos Filippitzis ◽  
Thomas Heaton ◽  
Robert W. Clayton ◽  
Richard Guy ◽  
...  
Keyword(s):  
Los Angeles ◽  
Strong Motion ◽  
Ground Level ◽  
Site Amplification ◽  
Seismic Network ◽  
Los Angeles Basin ◽  
High Rise ◽  
The North ◽  
South Central ◽  
San Fernando

Abstract The populace of Los Angeles, California, was startled by shaking from the M 7.1 earthquake that struck the city of Ridgecrest located 200 km to the north on 6 July 2019. Although the earthquake did not cause damage in Los Angeles, the experience in high-rise buildings was frightening in contrast to the shaking felt in short buildings. Observations from 560 ground-level accelerometers reveal large variations in shaking in the Los Angeles basin that occurred for more than 2 min. The observations come from the spatially dense Community Seismic Network (CSN), combined with the sparser Southern California Seismic Network and California Strong Motion Instrumentation Program networks. Site amplification factors for periods of 1, 3, 6, and 8 s are computed as the ratio of each station’s response spectral values combined for the two horizontal directions, relative to the average of three bedrock sites. Spatially coherent behavior in site amplification emerges for periods ≥3  s, and the maximum calculated site amplifications are the largest, by factors of 7, 10, and 8, respectively, for 3, 6, and 8 s periods. The dense CSN observations show that the long-period amplification is clearly, but only partially, correlated with the depth to basement. Sites with the largest amplifications for the long periods (≥3  s) are not close to the deepest portion of the basin. At 6 and 8 s periods, the maximum amplifications occur in the western part of the Los Angeles basin and in the south-central San Fernando Valley sedimentary basin. The observations suggest that the excitation of a hypothetical high-rise located in an area characterized by the largest site amplifications could be four times larger than in a downtown Los Angeles location.

Britain and the new UN agenda: towards global riot control?

1991 ◽  
Vol 17 (1) ◽  
pp. 95-105
Author(s):  
Giorgios Kostakos ◽  
A. J. R. Groom ◽  
Sally Morphet ◽  
Paul Taylor
Keyword(s):  
Cold War ◽  
International Security ◽  
General Assembly ◽  
Significant Extent ◽  
The West ◽  
The North ◽  
The Cold War ◽  
Riot Control ◽  
Peace And War ◽  
East West

The fading away of the Cold War has allegedly shifted the attention of the Western members of the United Nations, as demonstrated by General Assembly speeches, towards issues like the environment, drugs and terrorism. The new issues moving towards the top of the international security agenda are more elusive than the traditional Peace- and War-related ones; nobody has control of a ‘button’ regarding these issues. An overall assessment of the situation shows that there is a great variety of actors involved, both governmental and non-governmental. It is also increasingly recognized that the East has similar interests to the West. As a result, the East–West divide is being bridged to a significant extent, while the North–South divide is being defined in new ways.

The Late Cenozoic evolution of the Aksu basin (Isparta Angle; SW Turkey). New insights

2011 ◽  
Vol 182 (2) ◽  
pp. 133-148 ◽  
Author(s):  
André Poisson ◽  
Fabienne Orszag-Sperber ◽  
Erdal Kosun ◽  
Maria-Angella Bassetti ◽  
Carla Müller ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Normal Faults ◽  
The West ◽  
Shallow Marine ◽  
Northern Margin ◽  
Sea Level Fluctuations ◽  
Marine Deposits ◽  
The North ◽  
Sw Turkey ◽  
Isparta Angle

Abstract The Mio-Pliocene basins around the Antalya gulf in SW Turkey developed above the Tauric Mesozoic platforms on which the Antalya nappes had been thrusted (in Late Cretaceous-Paleocene times). The closure of the initial Isparta Angle during these events (E-W compression) initiated the N-S orientation of the main structural lines, which persisted later and explains the orientation of the Aksu basin in contrast with the E-W orientation of the eastern Neo-gene Mediterranean basins. The area, and all southwestern Turkey, became emergent at the end of the Oligocene and were the site of shallow-marine carbonate deposits in the Chattian-Aquitanian, giving way to the wide Lycian basin in Burdigalian-Langhian times. The progressive emplacement of the Lycian nappes from the north over this basin provoked first its subsidence and then its emersion when the nappes attained their final position over the Bey Daglari platform in Langhian times. Coinciding, or in response to the Lycian nappes emplacement, the Aksu basin was initiated as an elongated N-S graben which was filled by thick accumulations of terrestrial and marine deposits(including coral reefs), which derived from the erosion of the Lycian allochton and its basement (Langhian?, Serravallian and Tortonian times). The syn-sedimentary tectonics : reactivation of the normal faults along the west margin of the basin, the continuous uplift of the neighbouring continental areas (beginning of the Aksu thrust), governed the geometry of the basin. As a result and due to the uplift of its northern margin, the Aksu basin migrated towards the south and in Messinian times it was reduced to a narrow gulf along the eastern margin of which the Gebiz limestones were deposited as fringing coral reefs. The age of these limestones has been debated. Our new data allow us to attribute them to the Messinian. The drastic retreat of the sea at the end of this period, provoked the erosion of large parts of the Messinian deposits and the formation of deep canyons on land and under the sea down to the Antalya abyssal plain, in which evaporites were deposited. During the Zanclean transgression, the Eskiköy-Kargi canyon was filled by coarse clastics of a Gilbert delta derived from the northern continental area following a model well known elsewhere in the Mediterranean basins. Southward, shallow-marine sands and marls unconformably cover the remnants of the Messinian deposits and the emergent areas of the southern Antalya gulf. After Zanclean times (end of Pliocene?), the Aksu basin was deformed, due to the west-directed Aksu compressional event (end of the Aksu thrust). Quaternary terraces of the Aksu river at various altitudes, as well as the terraces of the Antalya tufa can be related to sea level fluctuations.

scholarly journals The North Greenland fold belt in eastern Nansen Land

1985 ◽  
Vol 126 ◽  
pp. 69-78
Author(s):  
J.D Friderichsen ◽  
H.-J Bengaard
Keyword(s):  
Lower Cambrian ◽  
Upper Cretaceous ◽  
Field Work ◽  
Strike Slip ◽  
Fold Belt ◽  
Clastic Rocks ◽  
The North ◽  
Major Strike ◽  
East West ◽  
Strike Slip Movement

Field work in 1984 shows that Nansen Land consists of clastic rocks of the carbonaceous Paradisfjeld Group and terrigeneous rocks of the Polkorridoren Group; both are lower Cambrian in age and deposited in a slope and fan environment. Two major Ellesmerian (Devonian to Carboniferous) phases of deformation gave rise to east-west trending folds and schistosities. Three phases of Eurekan (upper Cretaceous to Tertiary) deformation, associated with dyke intrusion, are recognised. The second of these may be related to transpression on the Harder Fjord fault zone, though no major strike-slip movement seems to have taken place.

scholarly journals Origin and age of the Shenshan tectonic mélange in the Jiangshan-Shaoxing-Pingxiang Fault and late Early Paleozoic juxtaposition of the Yangtze Block and the West Cathaysia terrane, South China

2021 ◽  
Author(s):  
Lijun Wang ◽  
Kexin Zhang ◽  
Shoufa Lin ◽  
Weihong He ◽  
Leiming Yin
Keyword(s):  
South China ◽  
Strike Slip ◽  
Carbonaceous Shale ◽  
Early Paleozoic ◽  
Yangtze Block ◽  
The West ◽  
Northern Margin ◽  
The North ◽  
Tectonic Mélange ◽  
Different Parts

When and how the Yangtze Block (Yangtze) and the West Cathaysia terrane (West Cathaysia) in South China were amalgamated are critical to a better understanding of the Neoproterozoic to early Paleozoic tectonic evolution of South China and remain highly debatable. A key to this debate is the tectonic significance of the Jiangshan-Shaoxing-Pingxiang (JSP) Fault, the boundary between Yangtze and West Cathaysia. The Shenshan mélange along the JSP Fault has the typical block-in-matrix structure and is composed of numerous shear zone-bounded slivers/lenses of rocks of different types and ages that formed in different tectonic environments, including middle to late Tonian volcanic and volcanogenic sedimentary rocks (turbidite) of arc/back-arc affinity, a series of middle Tonian ultramafic to mafic plutonic rocks of oceanic island basalt affinity, a carbonaceous shale that was deposited in a deep marine environment, and a red mudstone. U-Pb zircon ages and acritarch assemblages (Leiosphaeridia-Brocholaminaria association) found in the turbidite confirm its Tonian age, and fossils from the carbonaceous shale (Asteridium-Comasphaeridium and Skiagia-Celtiberium-Leiofusa) constrains its age to the Early to Middle Cambrian. Field relationships and available age data leave no doubt that the ultramafic-mafic rocks are exotic blocks (rather than intrusions) in the younger metasedimentary rocks. We conclude that the Shenshan mélange is not an ophiolitic mélange, but rather a tectonic mélange that formed as a result of movement along the JSP Fault in the early Paleozoic. We suggest that Yangtze and West Cathaysia were two separate microcontinents, were accreted to two different parts of the northern margin of Gondwana in the early Early Paleozoic, and juxtaposed in the late Early Paleozoic through strike-slip movement along the JSP Fault. We further suggest that the ca. 820 Ma collision in the Jiangnan Orogen took place between Yangtze and a (micro)continent that is now partly preserved as the Huaiyu terrane and was not related to West Cathaysia. We compare our model for South China with the accretion of terranes in the North American Cordillera and propose a similar model for the relationship between the Avalon and Meguma terranes in the Canadian Appalachians, i.e., the two terranes were accreted to two different parts of the Laurentian margin and were later juxtaposed through margin-parallel strike slip faulting.

scholarly journals Generasjoner imellom: Holdninger til familiens ansvar øst og vest i Europa

2019 ◽  
Vol 33 (0) ◽  
pp. 34
Author(s):  
Katharina Herlofson ◽  
Svein Olav Daatland ◽  
Marijke Veenstra
Keyword(s):  
Western Europe ◽  
Family Responsibility ◽  
The West ◽  
Older Parents ◽  
North West ◽  
The North ◽  
And Gender ◽  
Almost All ◽  
Eastern And Western Europe ◽  
East West

The article addresses the strength and character of family responsibility norms in Eastern and Western Europe. The strength is measured by the level of support for filial and parental responsibilities (i.e., adult children’s obligations towards older parents and vice-versa) and the character is indicated by the priority given to the older or the younger generation. For the analyses, we employ data from thirteen Eastern and Western European countries participating in the Generations and Gender Survey. In general, family norms are stronger in the East than in the West, but it is difficult to establish where to draw a dividing line. The contrast between the two extremes, Norway and Sweden in the north-west and Georgia in the south-east, is striking. The remaining countries line up quite close along the geographical diagonal (from Scandinavia to Georgia). The character of the norms is less clearly distributed – whereas almost all countries in Eastern Europe give priority to the older generation, the picture in the West is more mixed. The results partly confirm earlier conclusions about east-west differences in family responsibility norms, but adding more countries to the analyses has revealed a more complex and ambiguous picture than presented in previous studies.

V.—Two Bronze Age Cairns in South Wales: Simondston and Pond Cairns, Coity Higher Parish, Bridgend

Archaeologia ◽  
1938 ◽  
Vol 87 ◽  
pp. 129-180 ◽  
Author(s):  
Cyril Fox
Keyword(s):  
Bronze Age ◽  
East Side ◽  
The West ◽  
Northern Margin ◽  
The North ◽  
Outstanding Feature ◽  
South Wales ◽  
The Town

In the angle between the rivers Ogwr and Ewenny on the northern margin of the Vale of Glamorgan, east of the town of Bridgend, Brackla Hill (287 ft.) is the outstanding feature. Its pastoral slopes are linked to higher ground on the north by a saddle, on the east side of which there is a gentle fall to a tributary of the Ewenny, and on the west to a rivulet which flows into the Ogwr. Coity village lies at the point where the saddle merges into the upland.

scholarly journals A reconstruction of Iberia accounting for W-Tethys/N-Atlantic kinematics since the late Permian-Triassic

2020 ◽  
Author(s):  
Paul Angrand ◽  
Frédéric Mouthereau ◽  
Emmanuel Masini ◽  
Riccardo Asti
Keyword(s):  
Plate Boundary ◽  
Strike Slip ◽  
Late Permian ◽  
Seismic Profiles ◽  
The West ◽  
Geological Evidence ◽  
The North ◽  
Kinematic Evolution ◽  
Well Data ◽  
Strike Slip Movement

Abstract. The West European kinematic evolution results from the opening of the West Neotethys and the Atlantic oceans since the late Paleozoic and the Mesozoic. Geological evidence shows that the Iberian domain well preserved the propagation of these two rift systems and is therefore key to significantly advance our understanding of the regional plate reconstructions. The Late Permian-Triassic tectonic evolution of Iberian rift basins shows that they have accommodated significant extension, but this tectonic stage is often neglected in most plate kinematic models, leading to the overestimation of the movements between Iberia and Europe during the subsequent Mesozoic (Early Cretaceous) rift phase. By compiling existing seismic profiles and geological constraints along the North Atlantic margins, including well data over Iberia, as well as recently published kinematic and paleogeographic reconstructions we propose a coherent kinematics model of Iberia that considers both the Neotethyan and Atlantic evolutions. Our model shows that the Europe-Iberia plate boundary was a domain of distributed and oblique extension made of two rift systems, in the Pyrenees and in the Iberian intra-continental basins. It differs from standard models that consider left-lateral strike-slip movement localized only in the northern Pyrenees in introducing a significant strike-slip movement south of Ebro accounting for Late Permian-Triassic extension and by emphasizing the need for an Ebro microcontinent. At a larger scale it emphasizes the role played by the late Permian-Triassic rift and magmatism, as well as strike-slip faulting in the evolution of the western Neotethyan Ocean and their control on localization of the Atlantic rift.

scholarly journals Ambient noise Love wave attenuation tomography for the LASSIE array across the Los Angeles basin

2021 ◽  
Vol 7 (22) ◽  
pp. eabe1030
Author(s):  
Xin Liu ◽  
Gregory C. Beroza ◽  
Lei Yang ◽  
William L. Ellsworth
Keyword(s):  
Los Angeles ◽  
Wave Attenuation ◽  
Plate Boundary ◽  
Seismic Attenuation ◽  
Supplementary Information ◽  
Los Angeles Basin ◽  
The North ◽  
Attenuation Structure ◽  
Earthquake Faults ◽  
Seismic Attenuation Tomography

The Los Angeles basin is located within the North America–Pacific plate boundary and contains multiple earthquake faults that threaten greater Los Angeles. Seismic attenuation tomography has the potential to provide important constraints on wave propagation in the basin and to provide supplementary information on structure in the form of the distribution of anelastic properties. On the basis of the amplitude information from seismic interferometry from the linear LASSIE array in the Los Angeles basin, we apply station-triplet attenuation tomography to obtain a 2D depth profile for the attenuation structure of the uppermost 0.6 km. The array crosses four Quaternary faults, three of which are blind. The attenuation tomography resolves strong attenuation (shear attenuation Qs ~ 20) for the fault zones and is consistent with sharp boundaries across them.

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