Detecting Transient Creep Events on the Ismetpasa Segment of the North Anatolian Fault with Continuous GNSS Time Series

2021 ◽  
Author(s):  
Alpay Özdemir ◽  
Uğur Doğan ◽  
Jorge Jara ◽  
Romain Jolivet ◽  
Semih Ergintav ◽  
...  
Keyword(s):  
Time Series ◽  
Sampling Rate ◽  
Slip Rate ◽  
Principal Component ◽  
Temporal Variations ◽  
North Anatolian Fault ◽  
Seismogenic Zone ◽  
Aseismic Slip ◽  
The North ◽  
Gnss Time Series

<p>Twenty six years after the Mw 7.3 Bolu/Gerede Earthquake of 1944, Ambraseys (1970) first recognized, in the offset of a manmade wall constructed across the fault in 1957, the signature of slow aseismic slip along the central segment of the North Anatolian Fault (NAF). Following this discovery, many studies have characterized the behaviour of this aseismic slip with land- and space-based geodetic techniques, and with creepmeters. It is now recognized that the rate of aseismic slip decreases logarithmically from more than 3 cm/yr in the years following the Gerede Earthquake to approximately 6±2 mm/yr today. Of this rate, approximately 1.2 mm/year is residual afterslip and the remainder appears to be linear creep interrupted by creep events. In the last two decades, InSAR allowed the derivation of maps of ground velocities that indicates aseismic slip extends along a 100-km-long section of the fault, with a spatially variable aseismic slip rate, reaching its peak value approximately 15-24 km east of the city of Ismetpasa. Furthermore, creepmeter measurements and InSAR time series indicate that surface aseismic slip in the region of Ismetpasa is largely episodic, alternating between quiescent periods and transient episodes of relatively rapid aseismic slip. These observations raise questions about how slip accommodates tectonic stress along the fault with significant implications in terms of hazard along the seismogenic zone.</p><p> In July 2016, we established ISMENET (Ismetpasa Continuous GNSS Network) to monitor spatial and temporal variations in the aseismic slip rate and detect slow slip events along the fault. ISMENET stations are distributed along 120 km long segment of the fault. In order to explore the shallow, fine spatio-temporal behavior of aseismic slip, 19 stations are located within 200 m to 10 km of the fault with 30 and 1 sec sampling rate. We analysed the GNSS time series to extract the signature of aseismic slip using a principal component analysis to reduce the influence of non-tectonic noise. We compared results with creep events quantified by creepmeters.</p><p>Keywords: Ismetpasa, Aseismic slip, GNSS, PCA, Time Series Analysis, NAFZ</p>

Detecting Transient Creep Events on the Ismetpasa Segment of the North Anatolian Fault with Continous GNSS Time Series

2020 ◽  
Author(s):  
Alpay Özdemir ◽  
Uğur Doğan ◽  
Jorge Jara ◽  
Ziyadin Çakır ◽  
Romain Jolivet ◽  
...  
Keyword(s):  
Time Series ◽  
Slip Rate ◽  
Principal Component ◽  
Temporal Variations ◽  
North Anatolian Fault ◽  
Seismogenic Zone ◽  
Aseismic Slip ◽  
Slow Slip Events ◽  
The North ◽  
Gnss Time Series

<p>Twenty six years after the Mw 7.3 Gerede Earthquake in1944, Ambraseys (1970) first recognized, in the offset of a manmade wall, the signature of slow aseismic slip along the central segment of the North Anatolian Fault (NAF). Following this discovery, many studies characterized the behavior of aseismic slip with land-and space-based geodetic techniques, including creepmeters. It is now well recognized that the aseismic slip rate decreases logarithmically from more than 3 cm/yr in the years following the Gerede Earthquake to approximately 6±2 mm/yr today. In the last two decades, InSAR allowed deriving maps of ground velocities suggesting that aseismic slip extends along a 100-km-long section of the fault. Furthermore, aseismic slip rate varies in space along strike, reaching its peak value approximately 15-24 km east of the city of Ismetpasa. Furthermore, creepmeter measurements and InSAR time series indicate that aseismic slip in the region of Ismetpasa behaves episodically rather than continuously, alternating quiescent periods and transient episodes of relatively rapid aseismic slip. These observations raise questions about how slip accommodates tectonic stress along the fault with significant implications in terms of hazard along the seismogenic zone.</p><p> </p><p>In order to monitore spatial and temporal variations in the aseismic slip rate and to detect slow slip events along the fault, we have established ISMENET -Ismetpasa Continuous GNSS Network- in July 2016. ISMENET stations are distributed over approximately 120 km along strike. In order to explore the shallow, fine spatio-temporal behavior of aseismic slip, stations are located within 200 m to 10 km of the fault. We process GNSS data with the Bernese (V5.2) and GAMIT/GLOBK (V10.7) GNSS software. We analyze the GNSS time series to extract the signature of aseismic slip using a principal component analysis to reduce the influence of non-tectonic noises.</p><p> </p><p>Keywords: Ismetpasa, Aseismic slip, GNSS, PCA, Time Series Analysis, NAFZ</p>

Slow slip events along the North Anatolian Fault

2021 ◽  
Author(s):  
Romain Jolivet ◽  
Bertrand Rouet-Leduc ◽  
Jorge Jara ◽  
Manon Dalaison ◽  
Claudia Hulbert ◽  
...  
Keyword(s):  
Time Series ◽  
Fault Plane ◽  
Slip Rate ◽  
North Anatolian Fault ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Temporal Scales ◽  
Slow Slip Events ◽  
Spatial And Temporal Scales ◽  
The North

<p>While some faults remain locked for tens to hundreds of years, some active faults slip slowly, either continuously or episodically. The discovery of slow, generally silent, slip at the turn of the century led to a profound modification of our understanding of the mechanics of faulting, shedding light on the dynamics of fault slip. Such dynamics areis controlled by the past history of stress along the fault plane (i.e. historical ruptures), fluids circulating in the crust and the rheology of the crust and fault plane. Understanding the influence of these different factors requires dense observations, as suggested by the large range of spatial and temporal scales involved in the control of the slip velocity along a fault. Specifically, the smallest scales of slow slip have beenwere inferred by the observation of tremors or low frequency events, interpreted as the chatter of a fault plane while it slips slowly. We are missing direct observations of such kilometer-scale slow slip events and continental creeping faults are an obvious target for such observationsfor such observations.</p><p> </p><p>Aseismic slip along the North Anatolian Fault was recognized in the 1960’s by the observation of offset man-made features without earthquakes recorded. Following these early observations, multiple geodetic studies focused on recording aseismic slip and analyzed the average rate of shallow slow slip in the vicinity of the town of Ismetpasa. GPS, InSAR and creepmeter data all converge toward an aseismic slip rate reaching 1 cm/yr in places, with significant along- strike variations. Furthermore, earlyHowever, creepmeter measurements in the 80’s, confirmed by records from a more recent instrument, suggest aseismic slip is currently episodic, occurring in bursts of slip. Recent InSAR data from the Cosmo-SkyMed constellation captured a month-long slow slip event with a maximum of 2 cm/yr of slip.</p><p> </p><p>We propose to analyze the geodetic record to search for slow slip events over the 2015-2020 period. We take advantage of a dense network of continuous GNSS stations installed in 2017 and of time series of Sentinel 1 SAR data to identify at least 3 slow slip events along the North Anatolian Fault. Thanks to the dense temporal sampling of the GNSS records, we describe faithfullyobserve the onset of slow slip. We use a deep learning algorithm to extract the surface signature of the slow slip events from the InSAR time series, highlighting a slow rupture front propagating along strike. We compare the occurrences of slow slip events with the local fault geometry, the average distribution of kinematic coupling and the historical seismicity. We discuss the mechanical implications of such detailed description of slow slip along an active fault. In conclusion, while slow slip rate averaged over periods longer than 2-3 years seems constant over the last 40 years, identification of slow slip events suggests this apparently constant rate results from slow slip events over multiple spatial and temporal scales.</p>

A geodetic exploration of the behavior of aseismic slip along the central section of the North Anatolian fault

2020 ◽  
Author(s):  
Jorge Jara ◽  
Alpay Ozdemir ◽  
Angelique Benoit ◽  
Romain Jolivet ◽  
Ziyadin Çakir ◽  
...  
Keyword(s):  
Time Series ◽  
Ground Deformation ◽  
North Anatolian Fault ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Central Section ◽  
Slow Slip Events ◽  
The North ◽  
Aseismic Deformation ◽  
Over Time

<p>Many geodetic evidence suggest aseismic slip along active faults is more common than previously thought. Furthermore, aseismic slip during the interseismic period seems to be made of intermittent slow slip events, corresponding to episodes of loading and releasing of tectonic stress over time. However, although our capabilities of detection and location of aseismic deformation have significantly increased together with the growth in available geodetic data, the physical mechanisms governing slow slip remain unknown.</p><p>We explore the spatial and temporal behavior of aseismic deformation in the vicinity of the small town of Ismetpasa, located along the central section of the North Anatolian Fault (Turkey). We combine InSAR and GNSS data acquired over the last 10 years to locate and quantify aseismic slip in the subsurface. We process SAR images (ALOS and Sentinel-1) acquired from 2007 to 2018 to build time series of ground deformation and maps of ground velocity. We confirm the presence of a 100 km-long creeping section, at rates of 10-20 mm/yr. Along this section, slip is not constant and decreases over time as formerly observed over the last 60 years. Furthermore, via a detailed analysis of our geodetic time series, we detect 3 major episodes of aseismic slip between 2015 and 2018, with durations ranging from 6 months to 1 year and magnitudes between 4.6 - 5.2. These results are compared with time series obtained from a network of GNSS permanent stations we have installed in the region (17 stations, period 2016 - 2019). As a conclusion, aseismic slip along this section of the North Anatolian Fault is characterized by slow slip events rather than by a constant, steady-state aseismic slip rate. We discuss the potential implications in terms of mechanics of slow slip along the NAF.</p>

scholarly journals Temporal variations of the fractal properties of seismicity in the western part of the north Anatolian fault zone: possible artifacts due to improvements in station coverage

1995 ◽  
Vol 2 (3/4) ◽  
pp. 147-157 ◽  
Author(s):  
A. O. Öncel ◽  
Ö. Alptekin ◽  
I. Main
Keyword(s):  
Fault Zone ◽  
Statistical Significance ◽  
Rock Fracture ◽  
Aegean Sea ◽  
B Value ◽  
Temporal Variations ◽  
North Anatolian Fault ◽  
North Anatolian Fault Zone ◽  
The North ◽  
Northern Aegean Sea

Abstract. Seismically-active fault zones are complex natural systems exhibiting scale-invariant or fractal correlation between earthquakes in space and time, and a power-law scaling of fault length or earthquake source dimension consistent with the exponent b of the Gutenberg-Richter frequency-magnitude relation. The fractal dimension of seismicity is a measure of the degree of both the heterogeneity of the process (whether fixed or self-generated) and the clustering of seismic activity. Temporal variations of the b-value and the two-point fractal (correlation) dimension Dc have been related to the preparation process for natural earthquakes and rock fracture in the laboratory These statistical scaling properties of seismicity may therefore have the potential at least to be sensitive short- term predictors of major earthquakes. The North Anatolian Fault Zone (NAFZ) is a seismicallyactive dextral strike slip fault zone which forms the northern boundary of the westward moving Anatolian plate. It is splayed into three branches at about 31oE and continues westward toward the northern Aegean sea. In this study, we investigate the temporal variation of Dc and the Gutenberg-Richter b-value for seismicity in the western part of the NAFZ (including the northern Aegean sea) for earthquakes of Ms > 4.5 occurring in the period between 1900 and 1992. b ranges from 0.6-1.6 and Dc from 0.6 to 1.4. The b-value is found to be weakly negatively correlated with Dc (r=-0.56). However the (log of) event rate N is positively correlated with b, with a similar degree of statistical significance (r=0.42), and negatively correlated with Dc (r=-0.48). Since N increases dramatically with improved station coverage since 1970, the observed negative correlation between b and Dc is therefore more likely to be due to this effect than any underlying physical process in this case. We present this as an example of how man-made artefacts of recording can have similar statistical effects to underlying processes.

scholarly journals An aseismic slip transient on the North Anatolian Fault

2016 ◽  
Vol 43 (7) ◽  
pp. 3254-3262 ◽  
Author(s):  
Baptiste Rousset ◽  
Romain Jolivet ◽  
Mark Simons ◽  
Cécile Lasserre ◽  
Bryan Riel ◽  
...  
Keyword(s):  
North Anatolian Fault ◽  
Aseismic Slip ◽  
The North

Locking Behavior of Main Marmara Fault in Western Turkey During Interseismic Period

2020 ◽  
Author(s):  
Zeynep Yılmaz ◽  
Ali Özgün Konca ◽  
Semih Ergintav
Keyword(s):  
3D Structure ◽  
Slip Rate ◽  
Fault Slip ◽  
North Anatolian Fault ◽  
Gps Data ◽  
Strain Accumulation ◽  
Sea Of Marmara ◽  
Western Turkey ◽  
The North ◽  
Fault Slip Rate

<p>The North Anatolian Fault (NAF) produced multiple earthquakes of M>7 throughout the 20th century, while the part of NAF beneath Sea of Marmara did not rupture during this period. Analysis of the Main Marmara Fault's interseismic behavior, the most active branch of the North Anatolian Fault in this region, in terms of locking depth and fault slip rate is critical for evaluating the region's seismic risk with a population of more than 20 million, as it provides information about the seismic moment deficit that may release in a potential future earthquake.</p><p>In this study, we modeled the Main Marmara Fault's interseismic locking with realistic geometry and 3D structure including sedimentary basins, by implementing a 3D finite element approach and using interseismic GPS velocities. We have optimized the fits with GPS data by evaluating cases where each fault segment is constrained by a fault slip rate below a predefined locking depth ranging from 0 to 20 km. Preliminary models reveal that a difference in locking depth is required between the Western Marmara and the eastern end of the Ganos Segment entering the Sea of Marmara. This result, which is consistent with seismicity studies and other previous studies using 1D profiles shows that the strain accumulation under Western Marmara is less and that the locking depths or couplings are not similar in these two segments. For the Princes' Islands Segment, further analysis is required due to complexity in the GPS data. Recent earthquakes along Silivri also indicate that the strain accumulation is complex with most mechanisms showing significant thrust component. We have also calculated various possible strain accumulation patterns and compared the strain rate field around the Main Marmara Fault. Our results show that in most cases the change in the seismicity of each segment is consistent with the interseismic behavior associated with its fault locking.</p><p>(This research has been supported by Boğaziçi University Scientific Research Projects Coordination Unit. Project Number: 15022, 2019)</p>

scholarly journals Towards Reliable Velocities of Permanent GNSS Stations

2016 ◽  
Vol 100 (1) ◽  
pp. 17-26
Author(s):  
Janusz Bogusz ◽  
Anna Klos ◽  
Marta Gruszczynska ◽  
Maciej Gruszczynski
Keyword(s):  
Time Series ◽  
Singular Spectrum Analysis ◽  
Principal Component ◽  
North East ◽  
Temporal Correlations ◽  
The North ◽  
Spatio Temporal ◽  
Permanent Station

Abstract In the modern geodesy the role of the permanent station is growing constantly. The proper treatment of the time series from such station lead to the determination of the reliable velocities. In this paper we focused on some pre-analysis as well as analysis issues, which have to be performed upon the time series of the North, East and Up components and showed the best, in our opinion, methods of determination of periodicities (by means of Singular Spectrum Analysis) and spatio-temporal correlations (Principal Component Analysis), that still exist in the time series despite modelling. Finally, the velocities of the selected European permanent stations with the associated errors determined following power-law assumption in the stochastic part is presented.

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