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>

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>

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>

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>

scholarly journals Three-dimensional deformation time series of glacier motion from multiple-aperture DInSAR observation

2019 ◽  
Vol 93 (12) ◽  
pp. 2651-2660 ◽  
Author(s):  
Sergey Samsonov
Keyword(s):  
Time Series ◽  
Surface Deformation ◽  
Ground Deformation ◽  
Three Dimensional ◽  
Data Sets ◽  
Ice Flow ◽  
The North ◽  
Glacier Ice ◽  
Deformation Component ◽  
3D Deformation

AbstractThe previously presented Multidimensional Small Baseline Subset (MSBAS-2D) technique computes two-dimensional (2D), east and vertical, ground deformation time series from two or more ascending and descending Differential Interferometric Synthetic Aperture Radar (DInSAR) data sets by assuming that the contribution of the north deformation component is negligible. DInSAR data sets can be acquired with different temporal and spatial resolutions, viewing geometries and wavelengths. The MSBAS-2D technique has previously been used for mapping deformation due to mining, urban development, carbon sequestration, permafrost aggradation and pingo growth, and volcanic activities. In the case of glacier ice flow, the north deformation component is often too large to be negligible. Historically, the surface-parallel flow (SPF) constraint was used to compute the static three-dimensional (3D) velocity field at various glaciers. A novel MSBAS-3D technique has been developed for computing 3D deformation time series where the SPF constraint is utilized. This technique is used for mapping 3D deformation at the Barnes Ice Cap, Baffin Island, Nunavut, Canada, during January–March 2015, and the MSBAS-2D and MSBAS-3D solutions are compared. The MSBAS-3D technique can be used for studying glacier ice flow at other glaciers and other surface deformation processes with large north deformation component, such as landslides. The software implementation of MSBAS-3D technique can be downloaded from http://insar.ca/.

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

Towards assessing the link between slow slip and seismicity with a Deep Learning approach

2020 ◽  
Author(s):  
Giuseppe Costantino ◽  
Mauro Dalla Mura ◽  
David Marsan ◽  
Sophie Giffard-Roisin ◽  
Mathilde Radiguet ◽  
...  
Keyword(s):  
Deep Learning ◽  
Subduction Zones ◽  
Surface Deformation ◽  
Short Term Memory ◽  
Ground Deformation ◽  
Japan Meteorological Agency ◽  
Joint Analysis ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Seismicity Rate

<p>The deployment of increasingly dense geophysical networks in many geologically active regions on the Earth has given the possibility to reveal deformation signals that were not detectable beforehand. An example of these newly discovered signals are those associated with low-frequency earthquakes, which can be linked with the slow slip (aseismic slip) of faults. Aseismic fault slip is a crucial phenomenon as it might play a key role in the precursory phase before large earthquakes (in particular in subduction zones), during which the seismicity rate grows as well as does the ground deformation. Geodetic measurements, e.g. the Global Positioning System (GPS), are capable to track surface deformation transients likely induced by an episode of slow slip. However, very little is known about the mechanisms underlying this precursory phase, in particular regarding to how slow slip and seismicity relate.</p><p>The analysis done in this work focuses on recordings acquired by the Japan Meteorological Agency in the Boso area, Japan. In the Boso peninsula, interactions between seismicity and slow slip events can be observed over different time spans: regular slow slip events occur every 4 to 5 years, lasting about 10 days, and are associated with a burst of seismicity (Hirose et al. 2012, 2014, Gardonio et al. 2018), whereas an accelerated seismicity rate has been observed over decades that is likely associated with an increasing shear stress rate (i.e., tectonic loading) on the subduction interface (Ozawa et al. 2014, Reverso et al. 2016, Marsan et al. 2017).</p><p>This work aims to explore the potential of  Deep Learning  for better characterizing the interplay between seismicity and ground surface deformation. The analysis is based on a data-driven approach for building a model for assessing if a link seismicity – surface deformation exists and to characterize the nature of this link. This has potentially strong implications, as (small) earthquakes are the prime observable, so that better understanding the seismicity rate response to potentially small slow slip (so far undetected by GPS) could help monitoring those small slow slip events. The statistical problem is expressed as a regression between some features extracted from the seismic data and the GPS displacements registered at one or more stations.</p><p>The proposed method, based on a Long-Short Term Memory (LSTM) neural network, has been designed in a way that it is possible to estimate which features are more relevant in the estimation process. From a geophysical point of view, this can provide interesting insights for validating the results, assessing the robustness of the algorithms and giving insights on the underlying process. This kind of approach represents a novelty in this field, since it opens original perspectives for the joint analysis of seismic / aseismic phenomena with respect to traditional methods based on more classical geophysical data exploration.</p>

Afterslip and slow slip events in the postseismic deformation of the 2016 Pedernales earthquake, Ecuador

2020 ◽  
Author(s):  
Frederique Rolandone ◽  
Jean-Mathieu nocquet ◽  
Patricia Mothes ◽  
Paul Jarrin ◽  
Mathilde Vergnolle
Keyword(s):  
Subduction Zones ◽  
Postseismic Deformation ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Plate Interface ◽  
Slow Slip Events ◽  
North East ◽  
Rupture Area ◽  
Slip Event ◽  
Seismic Swarms

<p>In subduction zones, slip along the plate interface occurs in various modes including earthquakes, steady slip, and transient accelerated aseismic slip during either Slow Slip Events (SSE) or afterslip. We analyze continuous GPS measurements along the central Ecuador subduction segment to illuminate how the different slip modes are organized in space and time in the zone of the 2016 Mw 7.8 Pedernales earthquake. The early post-seismic period (1 month after the earthquake) shows large and rapid afterslip developing at discrete areas of the megathrust and a slow slip event remotely triggered (∼100 km) south of the rupture of the Pedernales earthquake. We find that areas of large and rapid early afterslip correlate with areas of the subduction interface that had hosted SSEs in years prior to the 2016 earthquake. Areas along the Ecuadorian margin hosting regular SSEs and large afterslip had a dominant aseismic slip mode that persisted throughout the earthquake cycle during several years and decades: they regularly experienced SSEs during the interseismic phase, they did not rupture during the 2016 Pedernales earthquake, they had large aseismic slip after it. Four years after the Pedernales earthquake, postseismic deformation is still on-going. Afterslip and SSEs are both involved in the postseimsic deformation. Two large aftershocks (Mw 6.7 & 6.8) occurred after the first month of postseismic deformation in May 18, and later in July 7 2016 two other large aftershocks (Mw 5.9 & 6.3) occurred, all were located north east of the rupture. They may have triggered their own postseismic deformation. Several seismic swarms were identified south and north of the rupture area by a dense network of seismic stations installed during one year after the Pedernales earthquakes, suggesting the occurrence of SSEs. Geodetically, several SSEs were detected during the postseismic deformation either in areas where no SSEs were detected previously, or in areas where regular seismic swarms and repeating earthquakes were identified. The SSEs may have been triggered by the stress increment due to aftershocks or due to afterslip.</p>

scholarly journals Short-Term Interaction between Silent and Devastating Earthquakes in Mexico

2020 ◽  
Author(s):  
Víctor Cruz-Atienza ◽  
Josué Tago ◽  
Carlos Villafuerte ◽  
Meng Wei ◽  
Ricardo Garza-Girón ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Seismic Waves ◽  
Regional Scale ◽  
Slow Slip ◽  
Aseismic Slip ◽  
Short Term ◽  
Plate Interface ◽  
Slow Slip Events ◽  
Large Earthquakes

Abstract Triggering of large earthquakes on a fault that hosts aseismic slip or, conversely, triggering of slow slip events (SSE) by passing seismic waves involves seismological questions with major hazard implications. Just a few observations plausibly suggest that such interactions actually happen in nature. In this study we show that three recent devastating earthquakes in Mexico are likely related to SSEs, describing a cascade of events interacting with each other on a regional scale via quasi-static and/or dynamic perturbations. Such interaction seems to be conditioned by the transient memory of Earth materials subject to the “traumatic” stressing produced by the seismic waves of the great Mw8.2 Tehuantepec earthquake, which strongly disturbed the aseismic beating over a 650 km long segment of the subduction plate interface. Our results imply that seismic hazard in large populated areas is a short-term evolving function of seismotectonic processes that are often observable.

scholarly journals A preliminary catalogue of Hikurangi, New Zealand, Slow Slip Earthquakes, from January 2000 to February 2014

2021 ◽  
Author(s):  
◽  
B. Peter Baxter
Keyword(s):  
New Zealand ◽  
Temporal Evolution ◽  
Processing Route ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Slip Rates ◽  
The North ◽  
General Terms ◽  
Significant Step

<p>This thesis documents processing carried out on cGPS data from 115 sites in the North Island and the top of the South Island of New Zealand in order to produce a catalogue of slow slip events (SSEs) for the Hikurangi Margin covering the period Jan 2000 to Feb 2014. It covers the background to the concept of SSEs and the reporting to date on their occurrence along the Margin, the methods used in the processing and analysis, the results of each significant step, and discussion of the results.  It has been shown that the processing route adopted in this work has reduced the average noise levels in the cGPS data by up to 67%, and has eliminated virtually all correlated (“pink”) noise, thus enabling the detection of small-amplitude events (~ 2mm in cGPS signals).  One hundred and fifty events are catalogued in total, of which 137 are considered likely to be SSEs or similar. The catalogue includes estimates of the uncertainty in each parameter and is thus considered the most comprehensive to date. Sixteen of the inversion results were able to be directly compared with published information and showed satisfactory agreement on location and equivalent moment magnitudes.  The important aspects of the project that have been developed further than has been documented to date in the literature include: partitioning of the secular velocity field over the margin to allow the underlying tectonic signal to be better understood; detailed characterization of the temporal evolution of the SSEs; the identification of approximately 40 events that show slips in the opposite direction to that expected; and some preliminary conclusions concerning event scaling.  One of the objectives of the project was to identify whether there were fundamental differences in the characteristics of SSEs in the northeast and southwest of the margin. On the basis of the analyses to date, it appears that the events form a continuum, at least in terms of depth, temporal evolution, source slip rates and scaling, but in general terms the events in the southwest have been confirmed to be of longer duration than those in the northeast.  The project has identified further work that needs to be carried out or is ongoing in order to maximize the value of these new results.</p>

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