Seismogenic structures of the collision-subduction zone in the eastern Taiwan

The Taiwan orogenic belt is relatively young and active with an ongoing arc-continent collision since the middle Miocene. In this study, we systematically investigate the use of seismic tomography, focal-mechanism and distribution of earthquakes to analysis the seismogenic patterns in the collision-subduction zone in the eastern Taiwan, which can be delineated five seismogenic zones of the Longitudinal Valley Fault Seismic Zone (LVFZ), the Central Range Fault Seismic Zone (CRFZ), the Backbone Range Seismic Zone (BRSZ), the Ludao-Lanyu Fault Seismic Zone (LLFZ), and the Wadati-Benioff Seismic Zone (WBSZ).The LVFZ and CRFZ, formed along the collision zone between the Philippine Sea and the Eurasian Plates, earthquake focal mechanisms show P axes distributed in direction of 285-335&#176;, reflecting the compressive stress field due to the collision. The LVSZ is the collisional boundary between the Philippine Sea and Eurasian plates. The LLFZ is a high-angle, east-dipping reverse fault separating the Luzon Volcanic Arc and the North Luzon Trough. The Eurasian plate (the South China Sea oceanic crust) subducts beneath the Philippine Sea plat in the southeastern Taiwan forming the WBSZ to a depth of 160 km.The CRFZ, located along the eastern limb of Backbone Range, is formed by a zone of west-dipping reverse fault. In addition, the earthquakes on the BRSZ generated by normal and strike-slip faults at about 5-15 km depth which occur in response to left-lateral transtensional deformation by the collision. Earthquake focal mechanisms show P and T axes distributed in direction of 280-330&#176; and 20-70&#176;, respectively.

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Earthquake Focal Mechanisms in the New Madrid Seismic Zone

Seismological Research Letters ◽

10.1785/0220130140 ◽

2014 ◽

Vol 85 (2) ◽

pp. 257-267 ◽

Cited By ~ 10

Author(s):

G. A. Johnson ◽

S. P. Horton ◽

M. Withers ◽

R. Cox

Keyword(s):

Focal Mechanisms ◽

New Madrid Seismic Zone ◽

Seismic Zone ◽

Earthquake Focal Mechanisms ◽

New Madrid

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Time Variations in Earthquake Focal Mechanisms of the Racha-Dzhava Seismic Zone

Izvestiya Atmospheric and Oceanic Physics ◽

10.1134/s0001433819110136 ◽

2019 ◽

Vol 55 (11) ◽

pp. 1726-1733

Author(s):

L. A. Shumlianskaya ◽

V. Yu. Burmin

Keyword(s):

Focal Mechanisms ◽

Seismic Zone ◽

Earthquake Focal Mechanisms ◽

Time Variations

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Distributed earthquake focal mechanisms in the Aegean Sea

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.16842 ◽

2018 ◽

Vol 40 (3) ◽

pp. 1125 ◽

Cited By ~ 3

Author(s):

A. Kiratzi ◽

C. Benetatos ◽

Z. Roumelioti

Keyword(s):

Aegean Sea ◽

Strike Slip ◽

Focal Mechanisms ◽

Normal Faulting ◽

Small Magnitude ◽

The North ◽

Earthquake Focal Mechanisms ◽

Reverse Faulting ◽

Different Types ◽

Transform Fault Zone

Nearly 2,000 earthquake focal mechanisms in the Aegean Sea and the surroundings for the period 1912- 2006, for 1.5 <M<7.5, and depths from 0 to 170 km, indicate a uniform distribution and smooth variation in orientation over wide regions, even for the very small magnitude earthquakes. ~ 60% of the focal mechanisms show normal faulting, that mainly strikes ~E-W. However, a zone ofN-S normal faulting runs the backbone of Albanides-Hellenides. Low-angle thrust and reverse faulting is confined in western Greece (Adria-Eurasia convergence) and along the Hellenic trench (Africa-Eurasia). In the central Aegean Sea the effect of the propagating tip of the North Anatolian Fault into the Aegean Sea is pronounced and strike-slip motions are widely distributed. Shearing does not cross central Greece. Strike-slip motions reappear in the Cephalonia-Lefkada Transform Fault zone and in western Péloponnèse, which shows very complex tectonics, with different types of faulting being oriented favourably and operating under the present stress-field. Moreover, in western Péloponnèse the sense of the observed shearing is not yet clear, whether it is dextral or sinistral, and this lack of data has significant implications for the orientation of the earthquake slip vectors compared to the GPS obtained velocity vectors.

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SITE RESPONSE CHARACTERISTICS OF H/V SPECTRUM BY MICROTREMOR SINGLE STATION OBSERVATIONS AT PALU CITY, INDONESIA

Journal of Applied Geology ◽

10.22146/jag.7202 ◽

2015 ◽

Vol 5 (1) ◽

Author(s):

Pyi Soe Thein ◽

Subagyo Pramumijoyo ◽

Kirbani Sri Brotopuspito ◽

Wahyu Wilopo ◽

Junji Kiyono ◽

...

Keyword(s):

Environmental Planning ◽

Site Response ◽

Vertical Motion ◽

Fault System ◽

Seismic Zone ◽

Eurasian Plate ◽

Predominant Period ◽

The North ◽

Single Station ◽

Central Sulawesi

In this study, we estimated predominant period of an H/V spectrum in Palu City, Indonesia, by using microtremor single station observations. Sulawesi Island, eastern Indonesia, is located at the junction between the converging Pacific-Philippine, Indo- Australian Plates and the Eurasian Plate. One of the major structures in Central Sulawesi is the Palu- Koro Fault system, which extends NNW-SSE direction and cross-cuts Sulawesi along more than 300 km from the North Sulawesi trench passing southward through Palu Bay then turn to the southeast, connecting to the Matano and Lawanopo Faults and further eastward both faults join to Tolo trench. Several earthquakes have been known along Palu-Koro Fault system such as Gimpu earthquake (1905), Kulawi earthquake (1907), Kantewu earthquake (1934), and offshore Donggala earthquake (1968) which caused tsunami that destroyed 800 houses and killed 200 people at Donggala district. Palu City, located at the northern tip of Palu depression, is a capital of the Central Sulawesi Province. It is located in the active seismic zone of the Palu-Koro fault. Spectral ratios for horizontal and vertical motion (H/V) from single-station microtremor records were used to identify the predominant periods of the ground vi- brations. Understanding the parameters of predominant period[s] and seismichazard is important for mitigation and environmental planning of the Palu region. Keywords: H/V spectrum, predominant period[s], microtremor single station observation

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Mini-sosie high-resolution reflection survey of the Cottonwood Grove fault in northwestern Tennessee

Bulletin of the Seismological Society of America ◽

10.1785/bssa0780020838 ◽

1988 ◽

Vol 78 (2) ◽

pp. 838-854

Author(s):

John L. Sexton ◽

Paul B. Jones

Keyword(s):

High Resolution ◽

Middle Eocene ◽

Strike Slip ◽

New Madrid Seismic Zone ◽

Reverse Fault ◽

Seismic Zone ◽

Registered Trademark ◽

The North ◽

Paleozoic Rocks ◽

New Madrid

Abstract The Cottonwood Grove fault is located within a portion of the New Madrid seismic zone in northwestern Tennessee. Focal mechanism studies indicate that this area is a seismic transition zone. To the southwest is a southwest-northeast seismic trend in which movements along deeper seated faults is predominantly right-lateral strike-slip. To the north is a southeast-northwest seismic trend in which reverse and normal faulting predominate. The Cottonwood Grove fault is buried beneath the poorly consolidated sediments of the Mississippi embayment. The fault, as identified by an earlier Vibroseis ®* survey is a northeast-southwest trending, eastward-dipping reverse fault with approximately 75 m (245 ft) of displacement on the Paleozoc-Cretaceous boundary. A Mini-Sosie™† high-resolution seismic reflection survey was conducted through the village of Cottonwood Grove along the previously surveyed Vibroseis line to improve estimates of the age, geometry, and displacements of the Cottonwood Grove fault. Results of the Mini-Sosie survey reveal that displacements across the major fault are relatively consistent within Cretaceous, Paleocene, and middle Eocene sedimentary rocks. In upper Eocene and younger rocks, however, there is no evidence for faulting. Our interpretation includes a previously undetected secondary fault at the boundary between upper Cretaceous and Paleocene rocks. Also included in our interpretation of the subsurface profile through Cottonwood Grove is an Eocene age channel feature located 2 km east of the Cottonwood Grove fault. In addition, the Paleozoic-Cretaceous boundary is interpreted to be an erosional surface with no intrusives included in the Paleozoic rocks. Synthetic seismogram modeling, detailed gravity survey data, and theoretical gravity calculations support this interpretation, and indicate that shallow intrusive bodies within Paleozoic rocks are not needed to explain the observed data. Seismic reflections which would be expected if the intrusives were present are not observed, and the observed Bouguer gravity anomaly can be explained by use of irregularities on the erosional Paleozoic bedrock surface along with sedimentary features within the post-Paleozoic sediments. These data suggest that Cottonwood Grove fault formed during middle Eocene time and that since that time, any major movement on deeper faults has been predominantly strike-slip with little or no vertical reactivation. This interpretation is consistent with the prevailing hypotheses relating current seismicity of the New Madrid seismic zone to the contemporary regional compressive stress field acting on zones of weakness associated with the Precambrian Reelfoot Rift Complex. ®* Registered trademark of Conoco, Inc. ™† Registered trademark of Société Nationale Elf Aquitane (Production).

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An Update of Studies of the Bootheel Lineament in the New Madrid Seismic Zone, Southeastern Missouri and Northeastern Arkansas

Seismological Research Letters ◽

10.1785/gssrl.63.3.277 ◽

1992 ◽

Vol 63 (3) ◽

pp. 277-284 ◽

Cited By ~ 9

Author(s):

Eugene S. Schweig ◽

Ronald T. Marple ◽

Yong Li

Keyword(s):

Surface Deformation ◽

Shear Zones ◽

Surface Expression ◽

Seismic Zone ◽

Near Surface ◽

Ground Failure ◽

The North ◽

Seismogenic Structures ◽

New Madrid Earthquakes ◽

New Madrid

Abstract Five trenches across the Bootheel lineament, a possible surface expression of one of the coseismic faults of the great New Madrid earthquakes of 1811 and 1812, indicate that ground failure took place along this 135-km-long feature, probably in 1811 or 1812. The morphology and en echelon pattern of the north-northeast-trending lineament are suggestive of strike-slip displacement on a fault. Three trenches cross portions of the lineament along which liquefied sand was injected. Vertically displaced strata were observed in two of these trenches, but the displacement could be due to collapse caused by the removal of liquefied sand from below. Shear zones exposed in two other trenches do not appear to be directly related to liquefaction and may represent near-surface deformation associated with deeper deformation along potentially seismogenic structures.

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