Surface effects and tectonic setting of the 13 December 1982 North Yemen earthquake

1987 ◽  
Vol 77 (6) ◽  
pp. 2018-2037
Author(s):  
George Plafker ◽  
Robert Agar ◽  
A. H. Asker ◽  
M. Hanif
Keyword(s):  
Main Shock ◽  
Arabian Peninsula ◽  
Tectonic Setting ◽  
Tectonic Activity ◽  
Active Volcanism ◽  
The North ◽  
Surface Displacements ◽  
Southwestern Margin ◽  
Surface Manifestation ◽  
Epicentral Region

Abstract The North Yemen earthquake (Mb = 6.0) of 13 December 1982 is the first earthquake in the southern Arabian Peninsula known to be accompanied by surface displacements. The extensive destruction and loss of lives resulted entirely from widespread collapse of unreinforced masonry and mud brick structures; maximum Modified Mercalli intensity was probably VII to VIII. The only surface manifestation of tectonic activity was the occurrence of earthquake-related extensional ground cracks in the epicentral region. The cracks occur mainly in four relatively continuous north- to northwest-trending linear zones that range from a few hundred meters to 15 km in length and in irregular areas of polygonal extension cracks. The area within which the cracks occur is 22.5 km long by about 10 km wide. Continued dilation across some cracks was measured almost 1 month after the main shock. Seismicity and active volcanism in this region are inferred to reflect slow extension of the southwestern margin of the Arabia plate perpendicular to the Red Sea spreading axis.

St. Elias, Alaska, earthquake of February 28, 1979: Tectonic setting and precursory seismic pattern

1980 ◽  
Vol 70 (5) ◽  
pp. 1595-1606
Author(s):  
Omar J. Perez ◽  
Klaus H. Jacob
Keyword(s):  
Seismic Activity ◽  
Main Shock ◽  
Tectonic Setting ◽  
Space Time ◽  
North American Plate ◽  
Rupture Zone ◽  
The North ◽  
The Pacific ◽  
Time Patterns ◽  
Large Earthquakes

abstract The St. Elias earthquake of February 28, 1979 and two earlier earthquakes in the St. Elias Range, Alaska, are shown to have involved thrust motion on gently NNW-dipping faults associated with subduction of the Pacific beneath the North American Plate. The space-time patterns of the seismicity located within and in the immediate vicinity of the rupture zone of the St. Elias event in the 16-yr period prior to it, indicate approximately 6.3 yr of relative quiescence before the main shock, interrupted by a burst of seismic activity about 3 yr prior to the event. This observed seismic pattern resembles those reported for other large earthquakes, and therefore, we suggest that the preceding burst of activity may have been a precursor.

scholarly journals Analysis of tectonic activity of the North Anatolian Fault based on SBInSAR method

2018 ◽  
Vol 55 ◽  
pp. 00005 ◽  
Author(s):  
Karolina Owczarz
Keyword(s):  
North Anatolian Fault ◽  
Synthetic Aperture ◽  
Tectonic Activity ◽  
Sar Images ◽  
Synthetic Aperture Radar Interferometry ◽  
The North ◽  
Tectonic Faults ◽  
Surface Displacements ◽  
Active Tectonic ◽  
Small Baseline

The North Anatolian Fault situated in Turkey is one of the longest and most active tectonic faults in the world. The paper presents an analysis of tectonic activity in its area based on the method of Small Baseline Synthetic Aperture Radar Interferometry. For this purpose 73 satellite SAR images and specialized software GMT5SAR were used with implement the SBAS algorithm. In addition, the most important aspects of data processing and their final products were presented, which determined the surface displacements occurring in the surveyed area from 1 January 2014 to 1 March 2017. The displacements of the SBAS surface area ranged from -10 cm to +10 cm. Based on the obtained results and their analysis, the author also assessed the suitability of SBInSAR technology for areas of land displacement.

scholarly journals Statherian (ca. 1714–1680 Ma) Extension-Related Magmatism and Deformation in the Southwestern Korean Peninsula and Its Geological Significance: Constraints from the Petrological, Structural, Geochemical and Geochronological Studies of Newly Identified Granitoids

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 557
Author(s):  
Byung-Choon Lee ◽  
Weon-Seo Kee ◽  
Uk-Hwan Byun ◽  
Sung-Won Kim
Keyword(s):  
Korean Peninsula ◽  
Tectonic Setting ◽  
Alkali Feldspar ◽  
Ductile Deformation ◽  
Southwestern Part ◽  
The North ◽  
Deformation Event ◽  
Geochemical Analyses ◽  
A Minor ◽  
T Values

In this study, petrological, structural, geochemical, and geochronological analyses of the Statherian alkali feldspar granite and porphyritic alkali feldspar granite in the southwestern part of the Korean Peninsula were conducted to examine petrogenesis of the granitoids and their tectonic setting. Zircon U-Pb dating revealed that the two granites formed around 1.71 Ga and 1.70–1.68 Ga, respectively. The results of the geochemical analyses showed that both of the granites have a high content of K2O, Nb, Ta, and Y, as well as high FeOt/MgO and Ga/Al ratios. Both granites have alkali-calcic characteristics with a ferroan composition, indicating an A-type affinity. Zircon Lu-Hf isotopic compositions yielded negative εHf(t) values (−3.5 to −10.6), indicating a derivation from ancient crustal materials. Both granite types underwent ductile deformation and exhibited a dextral sense of shear with a minor extension component. Based on field relationships and zircon U-Pb dating, it was considered that the deformation event postdated the emplacement of the alkali feldspar granite and terminated soon after the emplacement of the porphyritic alkali feldspar granite in an extensional setting. These data indicated that there were extension-related magmatic activities accompanying ductile deformation in the southwestern part of the Korean Peninsula during 1.71–1.68 Ga. The Statherian extension-related events are well correlated with those in the midwestern part of the Korean and eastern parts of the North China Craton.

scholarly journals Increasing benthic vent formation: a threat to Japan’s ancient lake

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michio Kumagai ◽  
Richard D. Robarts ◽  
Yasuaki Aota
Keyword(s):  
Lake Biwa ◽  
Autonomous Underwater Vehicle ◽  
Tohoku Earthquake ◽  
Water Source ◽  
Tectonic Activity ◽  
Drinking Water Source ◽  
Sudden Increase ◽  
The North ◽  
Slow Earthquakes ◽  
Near Future

AbstractAn autonomous underwater vehicle (AUV) was deployed in Lake Biwa from 2000 to 2012. In December 2009, ebullition of turbid water was first found in the deepest area (> 90 m) of the North Basin. Follow-up investigations in April and December 2010 and January 2012 confirmed the existence of benthic vents similar to the vents observed in other deep lakes. Importantly, vent numbers per unit travel distance in Lake Biwa dramatically increased from only two vents (0.37 vents km−1) in December 2009 to 54 vents (5.28 vents km−1) in January 2012, which could be related to recent tectonic activity in Japan, e.g., the M9.1 Tohoku earthquake in March 2011 and slow earthquakes along the Nankai Trough from 2006 to 2018. Continuous back-up investigations from 2014 to 2019 revealed additional benthic vents in the same area. The sudden increase in benthic vent activity (liquid and gaseous ebullitions) have significant potential to alter lake biogeochemistry and, ultimately, degrade Japan’s major drinking water source and may be a harbinger of major crustal change in the near future.

The San Salvador Earthquake of October 10, 1986—Seismological Aspects and Other Recent Local Seismicity

1987 ◽  
Vol 3 (3) ◽  
pp. 419-434 ◽  
Author(s):  
Randall A. White ◽  
David H. Harlow ◽  
Salvador Alvarez
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
Vertical Plane ◽  
Aftershock Sequence ◽  
Central American ◽  
Fault Plane Solution ◽  
San Salvador ◽  
The North ◽  
Volcanic Chain ◽  
Plane Solution

The San Salvador earthquake of October 10, 1986 originated along the Central American volcanic chain within the upper crust of the Caribbean Plate. Results from a local seismograph network show a tectonic style main shock-aftershock sequence, with a magnitude, Mw, 5.6. The hypocenter was located 7.3 km below the south edge of San Salvador. The main shock ruptured along a nearly vertical plane toward the north-northeast. A main shock fault-plane solution shows a nearly vertical fault plane striking N32\sz\E, with left-lateral sense of motion. This earthquake is the second Central American volcanic chain earthquake documented with left-lateral slip on a fault perpendicular to the volcanic chain. During the 2 1/2 years preceeding the earthquake, minor microseismicity was noted near the epicenter, but we show that this has been common along the volcanic chain since at least 1953. San Salvador was previously damaged by a volcanic chain earthquake on May 3, 1965. The locations of six foreshocks preceding the 1965 shock show a distinctly WNW-trending distribution. This observation, together with the distribution of damage and a fault-plane solution, suggest that right-lateral slip occurred along a fault sub-parallel with Central American volcanic chain. We believe this is the first time such motion has been documented along the volcanic chain. This earthquake was also unusual in that it was preceded by a foreshock sequence more energetic than the aftershock sequence. Earlier this century, on June 08, 1917, an Ms 6.4 earthquake occurred 30 to 40 km west of San Salvador Volcano. Only 30 minutes later, an Ms 6.3 earthquake occurred, centered at the volcano, and about 35 minutes later the volcano erupted. In 1919 an Ms 6 earthquake occurred, centered at about the epicenter of the 1986 earthquake. We conclude that the volcanic chain is seismically very active with variable styles of seismicity.

Volcanic History and Tectonics of the North Langjökull Region, Central Iceland

1973 ◽  
Vol 10 (2) ◽  
pp. 164-179 ◽  
Author(s):  
J. D. A. Piper
Keyword(s):  
Late Pleistocene ◽  
Volcanic Activity ◽  
Active Zone ◽  
Ice Sheet ◽  
North Coast ◽  
Crustal Growth ◽  
Transform Fault ◽  
Active Volcanism ◽  
The North ◽  
Lava Pile

The geology of the area around the northern part of the Langjökull ice sheet in central Iceland is outlined. This area includes the termination of the western neovolcanic zone, two silicic centers, and basaltic interglacial, intraglacial, and postglacial volcanoes. The lava succession becomes older to the northwest of the area where the zone of young volcanoes gives away to a pile of lavas of pre-Bruhnes epoch age which dip at low angles towards the active zone.This active zone undergoes a change in strike from NE–SW to north–south near latitude 64 °55′N and the volcanoes north of this are smaller in volume than those on the southern extension of the zone. The area of Bruhnes epoch activity dies out above latitude 65 °10′N but much of the area between here and the north coast of Iceland was a line of volcanic activity during the preceding Matuyama epoch.The northern part of the western active zone in Iceland became inactive in late Pleistocene times, and the southern part of the zone is an area of continuing crustal growth. The zone of active volcanism does not terminate against a transform fault and crustal growth is accommodated by deformation of the crustal plate. Lines of crustal growth which subsequently die out can be invoked to explain the anticline and syncline structures in the lava pile and the currently-active Snaefellsnes zone in western Iceland.

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 The Zagreb (Croatia) M5.5 Earthquake on 22 March 2020

Geosciences ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 252 ◽  
Author(s):  
Snježana Markušić ◽  
Davor Stanko ◽  
Tvrtko Korbar ◽  
Nikola Belić ◽  
Davorin Penava ◽  
...  
Keyword(s):  
Structural Engineering ◽  
Main Shock ◽  
Residential Buildings ◽  
Tectonic Setting ◽  
Time Lapse ◽  
Earthquake Sequence ◽  
Epicentral Area ◽  
Local Soil ◽  
Seismic Amplification ◽  
Zagreb Area

On 22 March 2020, Zagreb was struck by an M5.5 earthquake that had been expected for more than 100 years and revealed all the failures in the construction of residential buildings in the Croatian capital, especially those built in the first half of the 20th century. Because of that, extensive seismological, geological, geodetic and structural engineering surveys were conducted immediately after the main shock. This study provides descriptions of damage, specifying the building performances and their correlation with the local soil characteristics, i.e., seismic motion amplification. Co-seismic vertical ground displacement was estimated, and the most affected area is identified according to Sentinel-1 interferometric wide-swath data. Finally, preliminary 3D structural modeling of the earthquake sequence was performed, and two major faults were modeled using inverse distance weight (IDW) interpolation of the grouped hypocenters. The first-order assessment of seismic amplification (due to site conditions) in the Zagreb area for the M5.5 earthquake shows that ground motions of approximately 0.16–0.19 g were amplified at least twice. The observed co-seismic deformation (based on Sentinel-1A IW SLC images) implies an approximately 3 cm uplift of the epicentral area that covers approximately 20 km2. Based on the preliminary spatial and temporal analyses of the Zagreb 2020 earthquake sequence, the main shock and the first aftershocks evidently occurred in the subsurface of the Medvednica Mountains along a deep-seated southeast-dipping thrust fault, recognized as the primary (master) fault. The co-seismic rupture propagated along the thrust towards northwest during the first half-hour of the earthquake sequence, which can be clearly seen from the time-lapse visualization. The preliminary results strongly support one of the debated models of the active tectonic setting of the Medvednica Mountains and will contribute to a better assessment of the seismic hazard for the wider Zagreb area.

scholarly journals Geological region by multi-signal method of gravity anomaly data in central Vietnam area

2021 ◽  
Vol 62 (5) ◽  
pp. 43-54
Author(s):  
Hong Thi Phan ◽  
Petrov Aleksey Vladimirovich ◽  
Phuong Minh Do ◽  
Luu Truong Nguyen ◽  
Keyword(s):  
Central Area ◽  
Tectonic Activity ◽  
Horizontal Gradient ◽  
Spectral Correlation ◽  
Sliding Windows ◽  
The North ◽  
Central Vietnam ◽  
Two Dimensional Filtering ◽  
Calculation Results ◽  
Signal Method

This paper presents the research results of applying the combined method of probabilistic statistical approaches, energy density spectral correlation, two-dimensional filtering in dynamic sliding windows, full horizontal gradient and heterogeneous axis tracking method to process and interpret the Bughe gravitational anomaly field in central area Vietnam. The calculation results have shown the superiority of the twodimensional filter in dynamic sliding windows compared to the filters in fixed windows in GEOSOFT software, GMT software. According to the physical characteristics of the field, the study area was divided into 13 homogeneous classes, this result is consistent with the geological-tectonic data in the area. In the north and northeast, the stabilized rock layers are characterized by homogeneous layers that extend in the northwestsoutheast direction. In the south and southwest, there is complex tectonic activity characterized by high density rock layers overlain by low density rock layers in each fault band with different directions of development. This suggests that there may be deeply buried mineral deposits of magmatic origin in central area Vietnam.

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