scholarly journals New data on the latest stress state of the earth’s crust on Sakhalin Island (based on structural and geomorphological indicators of tectonic stress)

2020 ◽  
Vol 4 (4) ◽  
pp. 372-383
Author(s):  
L.A. Sim ◽  
◽  
P.A. Kamenev ◽  
L.M. Bogomolov ◽  
◽  
...  
Keyword(s):  
Stress State ◽  
Crustal Deformation ◽  
Field Measurements ◽  
Field Work ◽  
Tectonic Stress ◽  
Strike Slip ◽  
The West ◽  
North Eastern ◽  
Central Sakhalin Fault ◽  
Entire Island

To verify the ideas about neotectonic and modern stresses of Sakhalin, we analyze structural and geomorphological signs of the stress state of this region, discovered during field work in 2019–2020. Along with updated field measurements using the structural-geomorphological method, data on crustal deformation based on GPS/GLONASS measurements are presented. Data from geophysical studies (seismological and borehole methods) are given. The identification of three types of areas with different geodynamic regime: transtension, transpression and strike – slip (simple shift) is confirmed. Variations of the current stress field at the boundaries of regions with different geodynamic regime for the formation of new faults are noted. Northern Sakhalin has specific directions of compression axes of neotectonic stresses, expressed in North-Eastern orientations, in contrast to the prevailing sublatitudinal orientations on the entire island. Studies have shown that in the south of Sakhalin, the border between the Amur and Okhotsk microplates runs along the West Sakhalin fault rather than the Central Sakhalin fault.

scholarly journals Study on the relationship between multi-stage strike-slip mechanism and basin evolution in Fangzheng fault depression

2018 ◽  
Vol 22 (4) ◽  
pp. 335-339
Author(s):  
Jingfeng Wu ◽  
Qi'an Meng ◽  
Xiaofei Fu ◽  
Yuling Ma ◽  
Meifeng Sun ◽  
...  
Keyword(s):  
Seismic Data ◽  
Structural Characteristics ◽  
Stage Structure ◽  
Tectonic Stress ◽  
Strike Slip ◽  
The West ◽  
Lateral Strike Slip ◽  
Slip Mechanism ◽  
Pull Apart Basin ◽  
Multi Stage

Fangzheng fault depression is controlled by the northern of the Tan-Lu fault zone. It undergoes multi-stage strike-slip, extrusion modification, and erosion of the thermal uplift, forming a tectonic pattern of uplifts connected with sags. Through the regional dynamic analysis, the study of the activity law of the western Pacific plate has clarified the formation and transformation of the regional tectonic stress field. Under the background of the multi-stage of the strike-slip mechanism in the northern part of the Tan-lu fault, the Fangzheng fault depression has a characteristic of the “left-lateral strike-slip pull-apart basin, right-lateral strike-slip extrusion transformation.” According to the difference of the strike-slip, the Fangzheng fault depression has divided into two parts: the East fault depression and the West fault depression. The seismic data, seismic attribute analysis, and geological modeling techniques have applied to analyze the two fault depressions, the East fault depression has actively controlled by the strike-slip activity, and the structure is complex. The seismic data quality is poor; the structure of the West Fault Depression is the opposite and structural characteristics of asymmetrical difference strike-slip in the East and West fault depressions. Interpretation of seismic sections through a slippery background, the strike-slip attributes of the whole fault depression from south to north are segmented, and the strike-slip mechanism from east to west is different. Under the control of the multi-stage strike-slip mechanism, the Fangzheng fault depression is divided into six stages of strike-slip evolution, corresponding to the six different stages of the strike-slip control basin, the formation process of the asymmetric difference strike-slip fault basin is clarified, which provides a reference for the study of the strike-slip pull-apart basin with multi-stage structure.

Seismic and geodetic response to crustal deformation in Krísuvík volcanic system, southwest Iceland

2020 ◽  
Author(s):  
Revathy M. Parameswaran ◽  
Ingi Th. Bjarnason ◽  
Freysteinn Sigmundsson
Keyword(s):  
Stress Field ◽  
Crustal Deformation ◽  
High Energy ◽  
Strike Slip ◽  
Normal Faults ◽  
Seismic Zone ◽  
The South ◽  
The West ◽  
Volcanic System ◽  
Geothermal Activity

<p>The Reykjanes Peninsula (RP) is a transtensional plate boundary in southwest Iceland that marks the transition of the Mid-Atlantic Ridge (MAR) from the offshore divergent Reykjanes Ridge (RR) in the west to the South Iceland Seismic Zone (SISZ) in the east. The seismicity here trends ~N80°E in central RP and bends to ~N45°E at its western tip as it joins RR. Seismic surveys, geodetic studies, and recent GPS-based kinematic models indicate that the seismic zone is a collection of strike-slip and normal faults (e.g., Keiding et al., 2008). Meanwhile, the tectonic processes in the region also manifest as NE-SW trending volcanic fissures and normal faults, and N-S oriented dextral faults (e.g., Clifton and Kattenhorn, 2006). The largest of these fissure and normal-fault systems in RP is the Krísuvík-Trölladyngja volcanic system, which is a high-energy geothermal zone. The seismicity here predominantly manifests RP’s transtentional tectonics; however, also hosts triggered events such as those following the 17 June 2000 Mw6.5 earthquake in the SISZ (Árnadottir et al., 2004) ~80 km east of Krísuvík. Stress inversions of microearthquakes from 1997-2006 in the RP indicate that the current stress state is mostly strike-slip with increased normal component to the west, indicating that the seismicity is driven by plate diverging motion (Keiding et al., 2009). However, the geothermal system in Krísuvík is a potential secondary source for triggered seismicity and deformation. This study uses seismic and geodetic data to evaluate the activity in the Krísuvík-Trölladyngja volcanic system. The seismic data is used to identify specific areas of focused activity and evaluate variations in the stress field associated with plate motion and/or geothermal activity over space and time. The data used, within the time period 2007-2016, was collected by the the South Icelandic Lowland (SIL) seismic network operated and managed by the Iceland Meterological Office (IMO). Furthermore, variations in seismicity are compared to crustal deformation observed with TerraSAR-X images from 2009-2019. Crustal changes in the Krísuvík area are quantified to develop a model for corresponding deformation sources. These changes are then correlated with the stress-field variations determined with seismic analysis.</p>

Ketilidian structure and the rapakivi suite between Lindenow Fjord and Kap Farvel, South-East Greenland

2000 ◽  
pp. 50-59
Author(s):  
Brian Chadwick ◽  
Adam A. Garde ◽  
John Grocott ◽  
Ken J.W. McCaffrey ◽  
Mike A. Hamilton
Keyword(s):  
Coastal Region ◽  
Field Work ◽  
Natural Environment Research Council ◽  
East Greenland ◽  
The North ◽  
Tectonic Processes ◽  
Field Investigations ◽  
North Eastern ◽  
Bad Weather ◽  
North Eastern Part

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Chadwick, B., Garde, A. A., Grocott, J., McCaffrey, K. J., & Hamilton, M. A. (2000). Ketilidian structure and the rapakivi suite between Lindenow Fjord and Kap Farvel, South-East Greenland. Geology of Greenland Survey Bulletin, 186, 50-59. https://doi.org/10.34194/ggub.v186.5215 _______________ The southern tip of Greenland is underlain by the Palaeoproterozoic Ketilidian orogen (e.g. Chadwick & Garde 1996; Garde et al. 1998a). Field investigations in the summer of 1999 were focused on the structure of migmatites (metatexites) and garnetiferous granites (diatexites) of the Pelite Zone in the coastal region of South-East Greenland between Lindenow Fjord and Kap Farvel (Figs 1, 2). Here, we first address the tectonic evolution in the Pelite Zone in that region and its correlation with that in the Psammite Zone further north. Then, the structure and intrusive relationships of the rapakivi suite in the Pelite Zone are discussed, including particular reference to the interpretation of the controversial outcrop on Qernertoq (Figs 2, 8). Studies of the structure of the north-eastern part of the Julianehåb batholith around Qulleq were continued briefly from 1998 but are not addressed here (Fig. 1; Garde et al. 1999). The field study was keyed to an interpretation of the Ketilidian orogen as a whole, including controls of rates of thermal and tectonic processes in convergent settings. Earlier Survey field work (project SUPRASYD, 1992–1996) had as its principal target an evaluation of the economic potential of the orogen (Nielsen et al. 1993). Ensuing plate-tectonic studies were mainly funded in 1997–1998 by Danish research foundations and in 1999 by the Natural Environment Research Council, UK. The five-week programme in 1999 was seriously disrupted by bad weather, common in this part of Greenland, and our objectives were only just achieved. Telestation Prins Christian Sund was the base for our operations (Fig. 2), which were flown with a small helicopter (Hughes MD-500).

Outflow ignimbrite sheets from Late Carboniferous calderas, Currabubula Formation, New South Wales, Australia

1983 ◽  
Vol 120 (5) ◽  
pp. 487-503 ◽  
Author(s):  
J. McPhie
Keyword(s):  
New South ◽  
Sedimentary Facies ◽  
Late Carboniferous ◽  
The West ◽  
Pyroclastic Deposits ◽  
Flow Units ◽  
South Wales ◽  
Accretionary Lapilli ◽  
North Eastern ◽  
Thickness Variations

SummaryRegionally mappable, silicic, outflow ignimbrite sheets are interbedded with fluvial volcanogenic conglomerates and sandstones of the Late Carboniferous Currabubula Formation of north-eastern N.S.W. Four of the most widespread of these ignimbrites are described and defined as members. The oldest member is comprised of many thin, originally non-welded flow units. Interbedded accretionary lapilli horizons may indicate phreatomagmatic activity at vent during the eruption in addition to local rain-flushing of co-ignimbrite ash clouds. Of the three other members, two are multiple flow-unit sheets, 160–180 m in aggregate thickness. Substantial portions of these sheets were originally welded. The remaining member is a simple welded ignimbrite characterized by abundant spherulites and lithophysae. Irregular pre-eruption topography and contemporaneous erosion were responsible for thickness variations of the ignimbrite sheets. Some palaeovalleys, now delineated by the ignimbrites, persisted in spite of repeated pyroclastic influxes. Relic pumice, shards and crystal fragments are ubiquitous components of the sedimentary facies of the Currabubula Formation, and were probably derived from originally poorly consolidated pyroclastic deposits such as airfall ash layers and non-welded ignimbrites. No surface trace of the sources of these ignimbrites exists. However, internal facies, thickness variations and volumes of the ignimbrites indicate that they periodically emanated from a multiple-caldera terrain which was continuously active during the Late Carboniferous, and located several kilometres to the west of present exposures.

Rampart seismic zone of central Alaska

1983 ◽  
Vol 73 (3) ◽  
pp. 813-829
Author(s):  
P. Yi-Fa Huang ◽  
N. N. Biswas
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
B Value ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Lithospheric Plate ◽  
Normal Faults ◽  
Seismic Zone ◽  
The West ◽  
Fault Plane Solutions

abstract This paper describes the characteristics of the Rampart seismic zone by means of the aftershock sequence of the Rampart earthquake (ML = 6.8) which occurred in central Alaska on 29 October 1968. The magnitudes of the aftershocks ranged from about 1.6 to 4.4 which yielded a b value of 0.96 ± 0.09. The locations of the aftershocks outline a NNE-SSW trending aftershock zone about 50 km long which coincides with the offset of the Kaltag fault from the Victoria Creek fault. The rupture zone dips steeply (≈80°) to the west and extends from the surface to a depth of about 10 km. Fault plane solutions for a group of selected aftershocks, which occurred over a period of 22 days after the main shock, show simultaneous occurrences of strike-slip and normal faults. A comparison of the trends in seismicity between the neighboring areas shows that the Rampart seismic zone lies outside the area of underthrusting of the lithospheric plate in southcentral and central Alaska. The seismic zone outlined by the aftershock sequence appears to represent the formation of an intraplate fracture caused by regional northwest compression.

scholarly journals Temporal and spatial patterns on serra, Scomberomorus brasiliensis (Teleostei, Scombridae), catches from the fisheries on the Maranhão coast, Brazil

2001 ◽  
Vol 61 (4) ◽  
pp. 541-546 ◽  
Author(s):  
V. da BATISTA ◽  
N. N. FABRÉ
Keyword(s):  
Spatial Patterns ◽  
Relative Abundance ◽  
West Coast ◽  
The West ◽  
Temporal And Spatial Patterns ◽  
Eastern Brazil ◽  
North Eastern ◽  
Displacement Pattern ◽  
Temporal And Spatial ◽  
Demersal Species

The displacement pattern of the serra, Scomberomorus brasiliensis, in North-eastern Brazil was analyzed from landing data recorded from the fleet fishing serra. Serra fishery has two seasons: from September to February (demersal species plus serra), and from March to August (almost only large amounts of serra). S. brasiliensis relative abundance increases similarly along the coast from March, but decreases first on the West coast from June. Records indicate that serra is near the coast at least until September/October in Eastern grounds. From October to March (strongest spawning season) there is no record of shoals on the coast. We concluded that the Maranhão coast is just a part of the migration circuit of S. brasiliensis that may exceed 300 nautical miles.

scholarly journals Structural connections between Urals and West Siberia: the common stage on the boundary of Permian and Triassic periods

2019 ◽  
Vol 488 (3) ◽  
pp. 294-297
Author(s):  
V. N. Smirnov ◽  
K. S. Ivanov
Keyword(s):  
West Siberia ◽  
Strike Slip ◽  
Middle Urals ◽  
The Urals ◽  
The West ◽  
Open Part ◽  
The Middle Urals ◽  
Eastern Zone ◽  
Structural Connections ◽  
The Common

40Ar/39Ar-dating of the micas from the schists and blastomylonites collected from the fault which separates the Eastern zone of the Middle Urals dipped under the cover of the West Siberian plate from the open part of the geologic structures of the Urals, showed that the last phase of deformation was represented by a submeridional sinistral strike-slip faults with the age of 251 Ma. The appearance of the analyzed deformations practically exactly coincides in time with the formation of the grabens of meridional strike at the base of the West Siberian plate. 

scholarly journals The geology of the north-eastern corner of Greenland - photogeological studies and 1993 field work

1994 ◽  
Vol 161 ◽  
pp. 21-33
Author(s):  
H.F Jepsen ◽  
J.C Escher ◽  
J.D Friderichsen ◽  
A.K Higgins
Keyword(s):  
Field Work ◽  
Tectonic Activity ◽  
Mobile Belt ◽  
North East ◽  
The North ◽  
Upper Proterozoic ◽  
North Eastern ◽  
Field Season ◽  
Upper Boundary ◽  
Middle Proterozoic

Late Archaean and Early Proterozoic crust-forming events in North-East and eastern North Greenland were succeeded by Middle Proterozoic sedimentation and volcanic activity; Late Proterozoic through Tertiary sedimentation was interrupted by several periods of tectonic activity, including the Caledonian orogeny in East Greenland and the Mesozoic deformation of the Wandel Hav mobile belt. Photogeological studies helped pinpoint areas of special interest which were investigated during the short 1993 field season. Insights gained during field work include: the nature of the crystalline basement terrain in the Caledonian fold belt, redefinition of the upper boundary of the Upper Proterozoic Rivieradal sandstones, revision of Caledonian nappe terminology, and the northern extension of the Caledonian Storstrømmen shear zone.

Sign in / Sign up

Export Citation Format

Share Document