DOCSLIB.ORG

Seismotectonic Characteristics of the Taiwan Collision-Manila Subduction Transition the Effect of Pre-Existing Structures

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Seismotectonic Characteristics of the Taiwan Collision-Manila Subduction Transition the Effect of Pre-Existing Structures Journal of Asian Earth Sciences 173 (2019) 113–120 Contents lists available at ScienceDirect Journal of Asian Earth Sciences journal homepage: www.elsevier.com/locate/jseaes Seismotectonic characteristics of the Taiwan collision-Manila subduction transition: The effect of pre-existing structures T ⁎ Shao-Jinn China,b, Jing-Yi Lina,b, , Yi-Ching Yeha, Hao Kuo-Chena, Chin-Wei Liangb a Department of Earth Sciences, National Central University, No. 300, Jhongda Rd., Jhongli City, Taoyuan 32001, Taiwan, ROC b Center for Environmental Studies, National Central University, No. 300, Jhongda Rd., Jhongli City, Taoyuan 32001, Taiwan, ROC ARTICLE INFO ABSTRACT Keywords: Based on the distribution of an earthquake swarm determined from an ocean bottom seismometer (OBS) network Collision deployed from 20 August to 5 September 2015 in the northernmost part of the South China Sea (SCS) and data Subduction from inland seismic stations in Taiwan, we resolved a ML 4.1 earthquake occurring on 1 September 2015 as a NE- Taiwan SW-trending left-lateral strike-slip event that ruptured along the pre-existing normal faults generated during the Manila SCS opening phases. The direction of the T-axes derived from the M 4.1 earthquake and the background Ocean bottom seismometer L seismicity off SW Taiwan present high consistency, indicating a stable dominant NW-SE tensional stress for the Passive margin subducted Eurasian Plate (EUP). The distinct stress variations on the two sides of these reactivated NE-SW trending features suggest that the presence of pre-existing normal faults and other related processes may lessen the lateral resistance between the Taiwan collision and Manila subduction system, and facilitate the slab-pull process for the subducting portion, which may explain the NW-SE tensional stress environment near the tran- sition boundary in the northernmost part of the SCS. 1. Introduction affect the seismogenic signature (Bent, 2002; Talwani and Rajendran, 1991). Although rifting-related normal faults originating from the SCS Generally, different tectonic environments can be characterized by opening are widespread off SW Taiwan (Lester et al., 2014; McIntosh distinct seismogenic behaviors, such as extensional mechanisms at mid- et al., 2013; Yang et al., 2006; Yeh et al., 2012), and are positively ocean ridges and underthrusting earthquakes along subduction systems. involved in the Taiwan orogeny (Rau et al., 2012), their influences on However, when several important tectonic procedures are interwoven, the offshore Taiwan seismogenic structures and the collision-subduc- seismic activity is complicated and indiscernible. Located near the tion process remain questionable. However, only a few moderate to northernmost tip of the South China Sea (SCS), western Taiwan and its large earthquakes have been recorded near the area in the past decades. SW offshore are withstanding the arc-continental collision to the north, Conducting relevant discussions is difficult due to the lack of micro- which forms the Taiwan orogen (Fig. 1), and the subduction process to seismic records for offshore SW Taiwan. In this study, with the de- the south, which constitutes the Manila subduction zone. The transition ployment of an ocean bottom seismometer (OBS) network, we collected between collision and subduction is suggested to occur near the SW information for a ML 4.1 earthquake and its related swarm occurring off Taiwan offshore area (Kao et al., 2000; Liu et al., 2004; Shyu et al., SW Taiwan, which is generally considered to be a seismically inactive 2005) where the obvious bathymetric morphology reveals the presence area. The combination of the OBS and the Central Weather Bureau of a passive margin. Along this convergent belt, compressional stress (CWB) inland station data enables a better hypocenters localization and subparallel to the plate motion or the trench-normal direction should the determination of the focal mechanism for the ML 4.1 event. By dominate the regional seismicity. However, various seismogenic char- combining the regional seismicity distribution, the slab geometry and acteristics appear along this collision-subduction system (Hsu et al., the stress expression, we aim to discern the seismogenic environment 2009; Liao et al., 2008; Rau et al., 2012; Wu et al., 2009; Yang et al., along this Taiwan collision-Manila subduction system, which could be 2016), including high- and low-angle compression, trench-parallel and valuable for the estimation of tsunami and shaking hazards in Southeast trench-perpendicular extension and strike-slip effects. On the other Asia. hand, pre-existing structures inherited from ancient continental rifting process and changes in the nature of the lithosphere are thought to ⁎ Corresponding author at: Department of Earth Sciences, National Central University, Taiwan, ROC. E-mail address: [email protected] (J.-Y. Lin). https://doi.org/10.1016/j.jseaes.2019.01.014 Received 3 September 2018; Received in revised form 7 January 2019; Accepted 8 January 2019 Available online 17 January 2019 1367-9120/ © 2019 Elsevier Ltd. All rights reserved. S.-J. Chin et al. Journal of Asian Earth Sciences 173 (2019) 113–120 Fig. 1. Tectonic map and earthquake distribution of the northern-most South China Sea (SCS) and Taiwan orogen. Colored dots are earthquakes with ML >3(Wu et al., 2008, catalog updated until 2016); normal faults off SW Taiwan are modified from Yang et al. (2006) and Yeh et al. (2012). The black arrow represents the plate motion of the Philippine Sea Plate relative to the Eurasian Plate. Abbreviations in yellow rectangles represent the inland Central Weather Bureau (CWB) seismic stations used in this study. The two insets show the regional tectonics of the study area and the enlarged map for the distribution of the eight ocean bottom seismometers (OBSs). Yellow triangles show the OBSs. DF: Deformation front; EUP: Eurasian Plate; LA: Luzon Arc; LRTPB: Luzon-Ryukyu Transition Plate Boundary; MT: Manila Trench; PSP: Philippine Sea Plate; SCS: South China Sea. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) 2. Tectonic setting anomaly pattern, Hsu et al. (2004) interpreted an earlier stage of sea floor spreading occurring ∼37 Ma, which is bounded by the Lu- The active Taiwan orogen originating from arc-continent collision zon–Ryukyu transform plate boundary (LRTPB) to its east. The two between the Eurasian Plate (EUP) and the Philippine Sea Plate (PSP) sides of the LRTPB exhibit different tectonic environments. A relatively began approximately 5–6Ma(Teng, 1990; Tsai et al., 1977). The rapid thicker oceanic crust exists to the west, whereas a rifted continental convergence rates of 7 and 8.2 cm/yr revealed by plate reconstruction crust to the east (McIntosh et al., 2013). Based on seismic reflection (Seno et al., 1993) and geodetic analyses (Hsu et al., 2009; Yu et al., data, numerous normal faults, covered by syn-rift strata and postrift 1997), respectively, suggest an ongoing mountain building process in sediments, have been mapped for the entire northeastern portion of the the present. Due to the oblique convergence between the two plates, the SCS. Most of these faults cut through the upper crust, connecting from orogeny in the island propagates from north to south (Suppe, 1984). the seafloor to the detachment above the lower crust, or even down to Onshore and offshore southern Taiwan, where the EUP subducts east- the Moho (Lester et al., 2014; McIntosh et al., 2014; Yeh et al., 2012). ward beneath the PSP along the Manila Trench, are in an initial stage of Since the area between the northernmost Manila subduction zone collision (Huang et al., 1997; Kao et al., 2000; Reed et al., 1992). and southern Taiwan is considered a transition from subduction to in- The subducting oceanic crust in the SCS initially broke ∼32 Ma itial collision, previous works have used available seismological and based on the interpretation of marine magnetic lineations (Briais et al., geological data to obtain a better understanding of the boundary and 1993; Taylor and Hayes, 1983). Given a northeast-trending magnetic the tectonic processes occurring in the vicinity of this transition (e.g., 114 S.-J. Chin et al. Journal of Asian Earth Sciences 173 (2019) 113–120 Fig. 2. Vertical component waveforms recorded by the OBSs and inland stations and the focal mechanism of the 2015 ML 4.1 earthquake. Station codes are shown in left panel; the azimuths and polarities of first arrivals are shown in the right panel. Eakin et al., 2014; Huang et al., 2004; Liu et al., 1997; 2004; Yu, 2004). August to 5 September 2015 with a small spacing of 3.3–10.8 km (inset By using focal mechanisms, Kao et al. (2000) illustrated a clear Wadati- in Fig. 1). This OBS network was originally designed to monitor the Benioff zone to the south of 21.5°N. However, along with a lack of ground motion around some degassing spots located in the continental subduction-related seismicity, the Manila Trench loses its bathymetric slope of the NE tip of the SCS. However, the occurrence of the 1 Sep- definition north of 21.5°N, and its tectonic identity becomes unclear. tember 2015, ML 4.1 earthquake makes the network the best device to The connection between a typical collision zone and a subduction area further investigate the tectonic environment of this relatively inactive is the so-called deformation front (DF). The DF extends NNW from the seismic area. MicrOBS, the OBS we used in this study was developed by northern edge of the Manila Trench to the foot of the continental slope, the French Research Institute for Exploitation of the Sea (Ifremer) and progressively turns to a NNE-SSW direction before it enters inland (Auffret et al., 2004). Each MicrOBS contains one hydrophone and Taiwan and connects to the mountain belt (Fig. 1).
Load more

Recommended publications
  • ISC Data Cited in Research Publications in 2019
    ISC data cited in research publications in 2019 This list is a result of a special effort to put together a collection of scientific papers published during 2019 that used ISC data. The list is by no means exhaustive. The ISC has become such a familiar name that many researchers sadly fail to reference their use of the ISC data. To track publications that use one or more of the ISC dataset and services, we set up automatic alerts with Google Scholar for scientific papers that refer to ISC. The Google Scholar alerts return matches with different ways to refer to the ISC as normally done by authors, such as “International Seismological Centre”, “International Seismological Center”, “ISC-GEM”, “ISC-EHB” and “EHB” + ”seismic”. No doubt many more references can be found by using different search phrases. Below are the bibliographic references to the ~280 works in year 2019 as gathered by Google Scholar. The references to articles published in journals are listed first, followed by the references to other types of publications (e.g., chapters in books, reports, thesis, websites). The references are sorted by journal name. The vast majority of the references below belong to journal articles. Radulian, M., Bălă, A., Ardeleanu, L., Toma-Dănilă, D., Petrescu, registered earthquakes in the Arctic regions, Arctic Environmental L. and Popescu, E. (2019). Revised catalogue of earthquake Research, 19, 3, 123-128, http://doi.org/10.3897/issn2541- mechanisms for the events occurred in Romania until the end of 8416.2019.19.3.123. twentieth century: REFMC, Acta Geod. Geoph., 54, 1, 3-18, Turova, A.P.
    [Show full text]
  • Seismic Response of SDOF Systems Under Doublet Earthquakes
    Seismic response of SDOF systems under doublet earthquakes *Saman Yaghmaei-Sabegh1) 1) Department of Civil Engineering, University of Tabriz, Tabriz, Iran 1) [email protected] ABSTRACT A single event scenario has been adopted in seismic design process of buildings by current design codes however seismic sequences may influence the structural safety. On 11th August 2012, two earthquakes took place in East-Azerbaijan province in the north-western part of Iran. In this study, effect of different features of this special seismic sequence that is named “doublet events” has been considered in the analysis. Artificial earthquake ground motion sequences are constructed based on real single events and results are compared with real sequences in terms of displacement time history. Results of analysis would help to highlight the effect of such type of motion in seismic evaluation of structures. 1. INTRODUCTION Based on observations in the past, the seismic events with strong or moderate intensity levels may be followed by aftershocks with considerable level of intensity. Large aftershocks after the mainshocks of the 2010 Haiti (Mw=7.0), 2010 Chile (Mw=8.8), 2008 Sichuan, China (Mw=8.0), 2011 Tohoku (Mw=9.0), 2009 L’Aquila, Italy earthquakes caused considerable structural and non-structural damages in suffering regions. Building seismic design codes does not typically provide any explicit guideline to consider seismic sequences effect on analysis or design procedures. A large body of literature exists about seismic sequences effects (or multiple events) on nonlinear behavior of buildings (Parisi and Augenti 2013; Zhai et al. 2013; Penna et al 2014). However, Seismic sequences studies have frequently been focused on mainshock-aftershock events in the past.
    [Show full text]
  • Damage and Ground Motion of the 26 December 2006 Pingtung Earthquakes, Taiwan
    Terr. Atmos. Ocean. Sci., Vol. 19, No. 6, 641-651, December 2008 doi: 10.3319/TAO.2008.19.6.641(PT) Damage and Ground Motion of the 26 December 2006 Pingtung Earthquakes, Taiwan Kou-Liang Wen1, 2, 3, *, Yu-Wen Chang 2, Che-Min Lin1, Hsien-Jen Chiang1, and Ming-Wey Huang 3 1 Institute of Geophysics, National Central University, Chung-Li, Taiwan, ROC 2 National Center for Research on Earthquake Engineering, National Applied Research Laboratories, Taipei, Taiwan, ROC 3 National S&T Center for Disaster Reduction, National Applied Research Laboratories, Taipei, Taiwan, ROC Received 7 January 2008, accepted 26 September 2008 ABSTRACT Two consecutive large earthquakes eight minutes apart occurred offshore of Hengchun, Pingtung County of Taiwan at night on 26 December 2006. The seismic intensity in the Kaohsiung and Pingtung areas reached 5 according to the Central Weather Bureau’s intensity scale making them the strongest earthquakes in the Hengchun area in a century. These earthquakes were felt throughout Taiwan. Because the earthquakes were located not far offshore, seismic instruments at the Taipower’s Nuclear Power Plant No. 3 (NPP3) registered their largest motions since recording commenced at the site. As a result, unit 2 of NPP3 was shut down while Unit 1 remained operating at full capacity. Other damage that occurred during the Earthquake Doublet included building collapse, rock falls, structure and non-structural damage to buildings, fire, and damage to utilities such as gas, electricity, and telephone lines; liquefaction was also noted. In this paper, the shakemaps based on the source parameters and real-time observations were predicted and compared with the recorded shakemaps.
    [Show full text]
  • Ionospheric and Atmospheric Perturbations Due to Two Major Earthquakes (M [ 7.0)
    J. Earth Syst. Sci. (2021) 130:149 Ó Indian Academy of Sciences https://doi.org/10.1007/s12040-021-01650-x (0123456789().,-volV)(0123456789().,-volV) Ionospheric and atmospheric perturbations due to two major earthquakes (M [ 7.0) 1, 2 2 SANJAY KUMAR *, PRASHANT KUMAR SINGH ,ROHTASH KUMAR , 1 1 AKSINGH and R P SINGH 1Atmospheric Research Laboratory, Department of Physics, Banaras Hindu University, Varanasi 221 005, India. 2Department of Geo-Physics, Banaras Hindu University, Varanasi 221 005, India. *Corresponding author. e-mail: [email protected] MS received 16 October 2020; revised 10 March 2021; accepted 25 March 2021 The perturbation produced in the atmosphere/ionosphere associated with earthquake precursors during seismic activity of two major earthquakes which occurred on (1) 24 June 2019 in Indonesia (M = 7.3) and (2) on 19 August 2018 at Ndoi, Fiji (M = 8.2), are studied. Based on statistical analysis of total electron content (TEC) data, the presence of ionospheric perturbations 5 days before and after the main shock are found, which depends on the distance as well as direction of observation point from the epicentre. In general, ionospheric perturbations after the EQ at all the stations are found larger than that before the EQ. Probable mechanisms behind these perturbations associated with EQ are also being discussed. The ionospheric perturbations are observed at stations which are at larger distances from the epicentre, but not observed over other stations in different directions which are comparatively closer to the epicentre. These results suggest that seismic induced ionospheric anomaly is not isotropic in nature. Ozone data from three satellites: AIRS, OMI, and TOMS-like and MERRA-2 model are also analyzed 5 days before the EQ day and compared to the monthly average level.
    [Show full text]
  • On the Segmentation of the Cephalonia–Lefkada Transform Fault Zone (Greece) from an Insar Multi-Mode Dataset of the Lefkada 2015 Sequence
    remote sensing Article On the Segmentation of the Cephalonia–Lefkada Transform Fault Zone (Greece) from an InSAR Multi-Mode Dataset of the Lefkada 2015 Sequence Nikos Svigkas 1,2,3,* , Simone Atzori 2, Anastasia Kiratzi 1 , Cristiano Tolomei 2 , Andrea Antonioli 2, Ioannis Papoutsis 3, Stefano Salvi 2 and Charalampos (Haris) Kontoes 3 1 Department of Geophysics, Faculty of Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 2 Osservatorio Nazionale Terremoti, Istituto Nazionale di Geofisica e Vulcanologia, 00143 Roma, Italy 3 Institute of Space Applications and Remote Sensing, National Observatory of Athens, 15236 Athens, Greece * Correspondence: [email protected] Received: 17 July 2019; Accepted: 6 August 2019; Published: 8 August 2019 Abstract: We use Interferometric Synthetic Aperture Radar (InSAR) to study the Cephalonia–Lefkada Transform Fault Zone (CTF) in the Ionian Sea. The CTF separates continental subduction to the north from oceanic subduction to the south, along the Hellenic Subduction Zone. We exploit a rich multi-modal radar dataset of the most recent major earthquake in the region, the 17 November 2015 Mw 6.4 event, and present new surface displacement results that offer additional constraints on the fault segmentation of the area. Based on this dataset, and by exploiting available information of earthquake relocation, we propose a new rupture process for the 2015 sequence, complementary to those published already. Our modelling includes an additional southern fault segment, oblique to the segment related with the mainshock, which indicates that the CTF structure is more complex than previously believed. Keywords: InSAR; fault segmentation; Cephalonia–Lefkada Transform Fault; seismology 1. Introduction The Cephalonia–Lefkada Transform Fault Zone (CTF) in western Greece (Figure1a), connects two different subducting regimes: subduction of continental lithosphere to the north, with subduction of oceanic lithosphere to the south [1].
    [Show full text]
  • Fault Model of the 2012 Doublet Earthquake, Near the Up-Dip End Of
    Kubota et al. Progress in Earth and Planetary Science (2019) 6:67 Progress in Earth and https://doi.org/10.1186/s40645-019-0313-y Planetary Science RESEARCH ARTICLE Open Access Fault model of the 2012 doublet earthquake, near the up-dip end of the 2011 Tohoku-Oki earthquake, based on a near-field tsunami: implications for intraplate stress state Tatsuya Kubota1,2* , Ryota Hino2, Daisuke Inazu3 and Syuichi Suzuki2 Abstract On December 7, 2012, an earthquake occurred within the Pacific Plate near the Japan Trench, which was composed of deep reverse- and shallow normal-faulting subevents (Mw 7.2 and 7.1, respectively) with a time interval of ~10 s. It had been known that the stress state within the plate was characterized by shallow tensile and deep horizontal compressional stresses due to the bending of the plate (bending stress). This study estimates the fault model of the doublet earthquake utilizing tsunami, teleseismic, and aftershock data and discusses the stress state within the incoming plate and spatiotemporal changes seen in it after the 2011 Tohoku-Oki earthquake. We obtained the vertical extents of the fault planes of deep and shallow subevents as ~45–70 km and ~5 (the seafloor)–35 km, respectively. The down-dip edge of the shallow normal-faulting seismic zone (~30–35 km) deepened significantly compared to what it was in 2007 (~25 km). However, a quantitative comparison of the brittle strength and bending stress suggested that the change in stress after the Tohoku-Oki earthquake was too small to deepen the down-dip end of the seismicity by ~10 km.
    [Show full text]
  • Doublet Earthquake Triggering for the April 2014 Events in the Solomon Islands
    SSS05-P05 Japan Geoscience Union Meeting 2019 Doublet Earthquake Triggering for the April 2014 Events in the Solomon Islands *Calvin Luiramo Qwana1, Masatoshi Miyazawa2, James Mori2 1. Graduate School of Science, Kyoto University, 2. DPRI, Kyoto Univ. In 2014 at 20:14 (UTC) on April 12th and 12:36 on April 13th, a doublet earthquake with moment magnitudes of M7.6 and M7.4, respectively occurred near Makira Island (San Cristobal) in the Solomon Islands. The depths of the events were 27 km and 37 km, respectively (GCMT). To understand the interrelation between the first (M7.6) and second (M7.4) events , we check the role of Coulomb stress triggering on aftershocks that follow the M7.6 main shock and the coulomb failure stress changes on both of the focal mechanism nodal planes for the second event. To understand if the coulomb stress triggering played a role in the evolution of the triggered event M7.4 earthquake, we evaluate the transient aftershocks from the M7.6 to see if it promoted failure on the rupture plane for the second event (M7.4). We evaluate the doublet source process of the events and recover the slip distribution on each of the faults. We use an iterative inversion method by Kikuchi and Kanamori (1991) for the teleseismic P waveforms recorded from more than 20 stations of the Global Seismographic Network in a distance range of 30° to 90°. A fault plane with fixed strike and dip is placed in the region of the earthquake hypocenter and divided into subfaults, and a constant rupture velocity of 2.5 km/s is assumed.
    [Show full text]
  • IRIS Citations, 2019
    Abers, G. A., Adams, A. N., Haeussler, P. J., Roland, E., Shore, P. J., Wiens, D. A., Schwartz, S. Y., Sheehan, A. F., Shillington, D. J., Webb, S., & Worthington, L. L. (2019). Examining Alaska’s earthquakes on land and sea. EOS, 100. https://doi.org/https://doi.org/10.1029/2019EO117621 Abers, G. A., Mann, M. E., Daly, K. A., Castaneda, R. A. S., & Christensen, D. H. (2019). Oblique subduction at the end of the Aleutian slab beneath the Wrangell Volcanic Field. AGU. Aderhold, K., Bradley, A. C., Busby, R., Gomberg, J., & Bostock, M. (2019). Sea ice and the Alaska Transportable Array. Seismological Research Letters, 90(2B), 1038. https://doi.org/http://dx.doi.org/10.1785/0220190061 Aderhold, K., Busby, R., Woodward, R., Vernon, F., Frassetto, A., & Hedlin, M. (2019). Observing the ‘Spheres with the EarthScope Transportable Array. AGU. Adimah, N. I., & Padhy, S. (2019). Ambient noise Rayleigh wave tomography across the Madagascar island. Geophysical Journal International, 220(3), 1657-1676. https://doi.org/10.1093/gji/ggz542 Aflaki, M., Mousavi, Z., Ghods, A., Shabanian, E., Vajedian, S., & Akbarzadeh, M. (2019). The 2017 Mw 6 Sefid Sang earthquake and its implication for the geodynamics of NE Iran. Geophysical Journal International, 218(2), 1227-1245. https://doi.org/10.1093/gji/ggz172 Afonso, J. C., Salajegheh, F., Szwillus, W., Ebbing, J., & Gaina, C. (2019). A global reference model of the lithosphere and upper mantle from joint inversion and analysis of multiple data sets. Geophysical Journal International, 217(3), 1602-1628. https://doi.org/10.1093/gji/ggz094 Agrawal, M., Pulliam, J., Sen, M.
    [Show full text]
  • Seismic Response of SDOF Systems Under Doublet Earthquakes
    Seismic response of SDOF systems under doublet earthquakes *Saman Yaghmaei-Sabegh1) 1) Department of Civil Engineering, University of Tabriz, Tabriz, Iran 1) [email protected] ABSTRACT A single event scenario has been adopted in seismic design process of buildings by current design codes however seismic sequences may influence the structural safety. On 11th August 2012, two earthquakes took place in East-Azerbaijan province in the north-western part of Iran. In this study, effect of different features of this special seismic sequence that is named “doublet events” has been considered in the analysis. Artificial earthquake ground motion sequences are constructed based on real single events and results are compared with real sequences in terms of displacement time history. Results of analysis would help to highlight the effect of such type of motion in seismic evaluation of structures. 1. INTRODUCTION Based on observations in the past, the seismic events with strong or moderate intensity levels may be followed by aftershocks with considerable level of intensity. Large aftershocks after the mainshocks of the 2010 Haiti (Mw=7.0), 2010 Chile (Mw=8.8), 2008 Sichuan, China (Mw=8.0), 2011 Tohoku (Mw=9.0), 2009 L’Aquila, Italy earthquakes caused considerable structural and non-structural damages in suffering regions. Building seismic design codes does not typically provide any explicit guideline to consider seismic sequences effect on analysis or design procedures. A large body of literature exists about seismic sequences effects (or multiple events) on nonlinear behavior of buildings (Parisi and Augenti 2013; Zhai et al. 2013; Penna et al 2014). However, Seismic sequences studies have frequently been focused on mainshock-aftershock events in the past.
    [Show full text]
  • Characteristics on Fault Coupling Along the Solomon Megathrust Based On
    PUBLICATIONS Geophysical Research Letters RESEARCH LETTER Characteristics on fault coupling along the Solomon 10.1002/2016GL070188 megathrust based on GPS observations Key Points: from 2011 to 2014 • We deployed the first continuous GPS network at the Western Solomon Yu-Ting Kuo1, Chin-Shang Ku1,2, Yue-Gau Chen1, Yu Wang3, Yu-Nung Nina Lin4, Ray Y. Chuang5, Islands since 2011 2 6 2 1,2 • GPS record reveals significantly Ya-Ju Hsu , Frederick W. Taylor , Bor-Shouh Huang , and Hsin Tung different interseismic coupling ratios 1 2 between two adjacent segments on Department of Geosciences, National Taiwan University, Taipei, Taiwan, Institute of Earth Sciences, Academia Sinica, the Solomon megathrust Taipei, Taiwan, 3Earth Observatory of Singapore, Nanyang Technological University, Singapore, 4CGG, Singapore, • We identify a semipermanent asperity 5Department of Geography, National Taiwan University, Taipei, Taiwan, 6Institute for Geophysics, University of Texas at and a potential barrier to rupture, Austin, Austin, Texas, USA each corresponding to the subduction of geological features Abstract The Solomon megathrust along the western Solomon arc generated two megathrust earthquakes Supporting Information: in the past decade (Mw 8.1 in 2007 and Mw 7.1 in 2010). To investigate the interseismic deformation and • Supporting Information S1 inferred coupling on the megathrust, we deployed the first continuous GPS network in the Western Solomon Islands. Our 2011–2014 GPS data and the back slip inversion model show coupling ratio as high as 73% along Correspondence to: the southeastern 2007 rupture segment but only 10% on average along the segment of 2010 event. Based on Y.-G. Chen, [email protected] the spatial distribution of coseismic slip, aftershock clusters, derived coupling pattern, and paleogeodetic records, we discovered the former as a semipermanent asperity and the latter as a potential megathrust barrier.
    [Show full text]
  • Is the Eastern Denali Fault Still Active? Minhee Choi, David W
    https://doi.org/10.1130/G48461.1 Manuscript received 24 April 2020 Revised manuscript received 30 November 2020 Manuscript accepted 3 December 2020 © 2021 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license. Published online 5 February 2021 Is the Eastern Denali fault still active? Minhee Choi, David W. Eaton and Eva Enkelmann Department of Geoscience, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada ABSTRACT rocks, ranging from Cambrian to Late Triassic The Denali fault, a transcurrent fault system that extends from northwestern Canada age, while the Wrangellia terrane is a late Paleo- across Alaska toward the Bering Sea, is partitioned into segments that exhibit variable zoic island-arc assemblage overlain by Mesozo- levels of historical seismicity. A pair of earthquakes (M 6.2 and 6.3) on 1 May 2017, in ic flood basalts and sedimentary rocks (Cobbett proximity to the Eastern Denali fault (EDF), exhibited source mechanisms and stress con- et al., 2016). During the Jurassic and Cretaceous, ditions inconsistent with expectations for strike-slip fault activation. Precise relocation of the Insular superterrane was intruded by several ∼1500 aftershocks revealed distinct fault strands that are oblique to the EDF. Calculated older arcs, and later by the active Wrangell arc, patterns of Coulomb stress show that the first earthquake likely triggered the second one. which has migrated from southeast to northwest The EDF parallels the Fairweather transform, which separates the obliquely colliding Ya- since 28 Ma (Beranek et al., 2017). kutat microplate from North America. In our model, inboard transfer of stress is deforming The Yakutat microplate is presently mov- and shortening the mountainous region between the EDF and the Fairweather transform.
    [Show full text]
  • Nonlinear Response Analysis of SDOF Systems Subjected to Doublet
    Engineering Structures 110 (2016) 281–292 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Nonlinear response analysis of SDOF systems subjected to doublet earthquake ground motions: A case study on 2012 Varzaghan–Ahar events ⇑ Saman Yaghmaei-Sabegh a, , Jorge Ruiz-García b a Department of Civil Engineering, University of Tabriz, Tabriz, Iran b Facultad de Ingeniería Civil, Universidad Michoacana de San Nicolás de Hidalgo, Edificio C, Planta Baja, Ciudad Universitaria, 58040 Morelia, Mexico article info abstract Article history: A moderate earthquake ground motion with moment magnitude (Mw) 6.4 took place in the North- Received 28 February 2015 Western area of Iran on August 11, 2012, which was followed by an aftershock (Mw = 4.9) just 6 min Revised 14 November 2015 later. Eleven minutes after the first event, the affected area was struck by another moderate seismic event Accepted 19 November 2015 (Mw = 6.3) coming from a different seismogenic source. Earthquake ground motions of this special type Available online 29 December 2015 of seismic sequence were recorded in the cities of Varzaghan and Ahar. Therefore, the first part of this study investigated the energy distribution and frequency content characteristics of the Varzaghan– Keywords: Ahar earthquake ground motions records through wavelet transform analysis. The second part of this Doublet earthquake ground motion study presents the results of the nonlinear response of SDOF systems subjected to as-recorded Strength reduction factor Ductility demand Varzaghan–Ahar seismic sequences. The nonlinear response was measured in terms of constant- SDOF ductility strength reduction factors, R, and inelastic displacement ratios, IDR, which were compared with Wavelet analysis predictive capabilities of previously proposed predictive expressions that take into account seismic sequences.
    [Show full text]