Bimaterial interfaces at the Karadere segment of the North Anatolian Fault, northwestern Turkey

Najdahmadi, Bita; Bohnhoff, Marco; Ben‐Zion, Yehuda

doi:10.1002/2015jb012601

Cited by 34 publications

(39 citation statements)

References 78 publications

(158 reference statements)

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“…9). This contrast is not as large as across the San Andreas fault south of Hollister (McGuire & Ben-Zion 2005), but is comparable to values obtained for the San Andreas fault around San Gorgonio Pass , Hayward fault (Allam et al 2014b) and North Anatolian fault (Najdahmadi et al 2016). The obtained value reflects an average velocity contrast over the top 20 km of the crust.…”

Section: Discussionsupporting

confidence: 63%

“…Similar to previous studies (e.g. Allam et al 2014b;Najdahmadi et al 2016), we examine HPM in displacement seismograms with consecutive moving time windows of length 0.1 s (20 samples) that overlap by 1 sample. For each window, all three components of motion are combined in a 20×3 matrix, the covariance of the matrix is computed (Bulut et al 2012) and the largest eigenvalue and eigenvector of the covariance matrix (major axis of the polarization ellipse) are obtained.…”

Section: Resultsmentioning

confidence: 99%

“…13 and geological mapping near Hog Lake southeast of the array (Dor et al 2006). Stations at larger distance from the fault may record, in addition to the phases analysed in this work, also P and S body waves reflected within a low velocity fault zone layer (Yang et al 2014) and waves reflected from bimaterial fault interfaces to off-fault stations (Najdahmadi et al 2016). A recent deployment of a longer aperture array across the Clark fault at the same location of the BB array (Lin et al 2016) provides opportunities for analysing these and other signals indicative of the inner structure of the fault.…”

Section: Discussionmentioning

confidence: 99%

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Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Ben‐Zion

Ross

et al. 2017

Geophysical Journal International

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S U M M A R YLocal and teleseismic earthquake waveforms recorded by a 180-m-long linear array (BB) with seven seismometers crossing the Clark fault of the San Jacinto fault zone northwest of Anza are used to image a deep bimaterial interface and core damage structure of the fault. Delay times of P waves across the array indicate an increase in slowness from the southwest most (BB01) to the northeast most (BB07) station. Automatic algorithms combined with visual inspection and additional analyses are used to identify local events generating fault zone head and trapped waves. The observed fault zone head waves imply that the Clark fault in the area is a sharp bimaterial interface, with lower seismic velocity on the southwest side. The moveout between the head and direct P arrivals for events within ∼40 km epicentral distance indicates an average velocity contrast across the fault over that section and the top 20 km of 3.2 per cent. A constant moveout for events beyond ∼40 km to the southeast is due to off-fault locations of these events or because the imaged deep bimaterial interface is discontinuous or ends at that distance. The lack of head waves from events beyond ∼20 km to the northwest is associated with structural complexity near the Hemet stepover. Events located in a broad region generate fault zone trapped waves at stations BB04-BB07. Waveform inversions indicate that the most likely parameters of the trapping structure are width of ∼200 m, S velocity reduction of 30-40 per cent with respect to the bounding blocks, Q value of 10-20 and depth of ∼3.5 km. The trapping structure and zone with largest slowness are on the northeast side of the fault. The observed sense of velocity contrast and asymmetric damage across the fault suggest preferred rupture direction of earthquakes to the northwest. This inference is consistent with results of other geological and seismological studies.

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Section: Discussionsupporting

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Ben‐Zion

Ross

et al. 2017

Geophysical Journal International

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“…Observed FZHW and these relations were used in various studies to image properties of bimaterial fault interfaces at sections of the San Andreas fault in California (e.g. McGuire & Ben-Zion 2005;Zhao et al 2010;Share & Ben-Zion 2016), the North Anatolian fault in Turkey (Bulut et al 2012;Najdahmadi et al 2016) and other faults (e.g. Hough et al 1994;Zhao & Peng 2008;Yang et al 2015).…”

Section: Methodsmentioning

confidence: 99%

Internal structure of the San Jacinto fault zone at Jackass Flat from data recorded by a dense linear array

Qiu

Ben‐Zion

Ross

et al. 2017

Geophysical Journal International

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S U M M A R YThe internal structure of the Clark fault in the trifurcation area of the San Jacinto fault zone is imaged using seismograms recorded by a dense linear array (Jackass Flat, JF) crossing the surface trace of the fault and an adjacent array (TR) to the SW. Delay times between phase arrivals associated with ∼3500 local earthquakes and nine teleseismic events are used to estimate velocity variations within the arrays. The teleseismic P waves travel faster beneath the TR than the JF array, in contrast to larger scale tomographic results. Statistical analysis of local P-wave delay times indicates that the entire JF array, with an aperture of ∼400 m, is inside a low-velocity damage zone. This low-velocity zone is bounded on the NE side by a shallow bimaterial interface generating fault zone head waves, and it contains an inner zone of more intense damage generating fault zone trapped waves. The P-wave velocity contrast across the local bounding bimaterial interface is 10-15 per cent. The trapping structure is associated with a width of ∼200 m, S-wave velocity reduction of ∼35 per cent with respect to the surrounding rock, Q-value of ∼20 and depth of ∼3.5 km. The imaging results suggest that the main seismogenic fault is near the SW end of the JF array, in agreement with a prominent geomorphologic feature. The existence of intense local damage on the crustal block with faster larger scale velocity at depth is consistent with common propagation of earthquake ruptures in the area to the NW.

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“…1) revealed additional information on the structure of its two strands. The presence of different lithologies bounding the northern branch of the NAFZ has been inferred by Bulut et al [2012] and Najdahmadi et al [2016] by tracking fault head waves caused by the presence of a bimaterial interface. This is also consistent with a change in Moho signature and depth observed in the Istanbul Zone and has been attributed to either the presence of a thicker crust (Frederiksen et al [2015]) or a weak Moho underlain by a highly anisotropic layer [2015]).…”

Section: Introductionmentioning

confidence: 99%

Constraints on North Anatolian Fault zone width in the crust and upper mantle from S-wave teleseismic tomography

Papaleo¹,

Cornwell²,

Rawlinson³

2018

Preprint

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Abstract.We present high resolution S-wave teleseismic tomography images of the western segment of the North Anatolian Fault (NAFZ) in Turkey using teleseismic data recorded during the deployment period of the DANA array. The array comprised 66 stations with a nominal station spacing of 7 km, thus permitting a horizontal and vertical resolution of approximately 15 km. We use the current S-wave results with previously published P-wave teleseismic tomography to produce maps of relative V P /V S anomalies, which we use to highlight the difference in overall composition of the three terranes separated by the northern (NNAF) and southern (SNAF) branches of the NAFZ. Our results show a narrow S-wave low velocity anomaly beneath the northern branch of the NAFZ extending from the upper crust, where it has a width of ∼10 km, to the lower crust, where it widens to ∼30 km. This low velocity zone most likely extends into the upper mantle, where we constrain its width to be ≤50 km and interpret it as indicative of localised shear beneath the NNAF; this structure is similar to what has been observed for the NAFZ west of 32• and therefore we propose that the structure of the NNAF is similar to that of the NAFZ in the east. The SNAF does not show a very strong signature in our images and we conclude that it is most likely rooted in the crust, possibly accommodating deformation related to rotation of the Armutlu/Almacik Blocks situated between the two NAFZ branches. Keypoints:• An ∼15-km resolution teleseismic S-wave velocity model constrains width and depth of the North Anatolian Fault in the crust and upper mantle

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Bimaterial interfaces at the Karadere segment of the North Anatolian Fault, northwestern Turkey

Cited by 34 publications

References 78 publications

Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Internal structure of the San Jacinto fault zone at Blackburn Saddle from seismic data of a linear array

Internal structure of the San Jacinto fault zone at Jackass Flat from data recorded by a dense linear array

Constraints on North Anatolian Fault zone width in the crust and upper mantle from S-wave teleseismic tomography

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