Shallow Creep Along the 1999 Izmit Earthquake Rupture (Turkey) From GPS and High Temporal Resolution Interferometric Synthetic Aperture Radar Data (2011–2017)

Abstract

Characterizing the spatiotemporal evolution of creep is essential to constrain fault slip budget and understand creep mechanism. Studies based on interferometric synthetic aperture radar and Global Positioning System (GPS) satellite observations until 2012 have shown that the central segment of the 17 August 1999 Mw 7.4 Izmit earthquake on the North Anatolian Fault began slipping aseismically following the event. In the present study, we combine new interferometric synthetic aperture radar time series, based on TerraSAR‐X and Sentinel 1A/B radar images acquired over the period 2011–2017, with near‐field GPS measurement campaigns performed every 6 months from 2014 to 2016. The mean velocity fields reveal that creep on the central segment of the 1999 Izmit fault rupture continues to decay, more than 19 years after the earthquake, in overall agreement with models of postseismic afterslip decaying logarithmically with time for a long period of time. Along the fault section that experienced supershear velocity rupture during the Izmit earthquake creep continues with a rate up to ~ 8 mm/year. A significant transient accelerating creep is detected in December 2016 on the Sentinel‐1 time series, near the maximum creep rate location, associated with a total surface slip of 10 mm released in 1 month only. Additional analyses of the vertical velocity fields show a persistent subsidence on the hanging wall block of the Golcuk normal fault that also ruptured during the Izmit earthquake. Our results demonstrate that afterslip processes along the North Anatolian Fault east‐southeast of Istanbul are more complex than previously proposed as they vary spatiotemporally along the fault.

Does Deep Tectonic Tremor Occur in the Central‐Eastern Mediterranean Basin?

“…The absence of triggered tremor in the eastern Marmara Sea agrees with the absence of LFE/tremor activity accompanying the ∼50-daylong SSE along the Çınarcık Fault (Martínez-Garzón et al, 2019). The absence of ambient tremor associated with the ∼50-daylong SSE could be explained in two different ways: (1) the SSE occurred at shallow depth, consistent with the observation of shallow SSEs along adjacent segments of the North Anatolian Fault (Aslan et al, 2019;Rousset et al, 2016); or (2) the SSE occurred at the down-dip limit of the seismogenic zone, and thereby exhibited a similar behavior to that of long-term SSEs. The occurrence of shallow SSEs along adjacent segments of the North Anatolian Fault would support the shallow origin of the signal.…”

“…Izmit (Aslan et al, 2019) and the 1944 Ismetpasa earthquakes (Rousset et al, 2016). On 25 June 2016, a ~50-daylong SSE was recorded along the Çınarcık Fault below the eastern Sea of Marmara, which was interpreted as the strain release equivalent of a Mw 5.8 at the depth of 9 km (Martínez-Garzón et al, 2019).…”

“…The analysis of recent, high temporal resolution, geodetic data revealed the existence of temporal fluctuations of the creep rate with detection of accelerating bursts of shallow (i.e., 0–5 km) creep events along the segments of the North Anatolian Fault that ruptured during the 1999 Izmit (Aslan et al., 2019) and the 1944 Ismetpasa earthquakes (Rousset et al., 2016). On June 25, 2016, a ∼50‐daylong SSE was recorded along the Çınarcık Fault below the eastern Sea of Marmara, which was interpreted as the strain release equivalent of a M w 5.8 at the depth of 9 km (Martínez‐Garzón et al., 2019).…”

Surface creep rate distribution along the Philippine fault, Leyte Island, and possible repeating of Mw ~ 6.5 earthquakes on an isolated locked patch

“…For that purpose, we first show results of Synthetic Aperture Radar (SAR) interferometry (InSAR) timeseries analysis, which gives indication of fault creep along most part of the Philippine fault in northern Leyte. InSAR time-series analysis or stacking analysis using multiple SAR images has been successfully used to detect fault creeps including the San Andreas fault zone (e.g., Bürgmann et al 1998;Lindsey et al 2014a), Ismetpasa area of the North Anatolian fault (Çakir et al 2005;Kaneko et al 2013), Izmit section of the North Anatolian fault (Aslan et al 2019;Cakir et al 2012;Hussain et al 2016), Chaman fault (Fattahi and Amelung 2016), El Pilar fault in Venezuela (Pousse Beltran et al 2016), Haiyuan fault in China (Jolivet et al 2012), and Longitudinal Valley fault in Taiwan (Hsu and Bürgmann 2006). Next, we show that the slip of the 2017 Ormoc earthquake occurred on the only locked portion of the fault in northern Leyte, by performing a fault slip model inversion and comparing the result with the creep distribution.…”

Creep Burst Coincident With Faulting in Marble Observed in 4‐D Synchrotron X‐Ray Imaging Triaxial Compression Experiments

“…Creep rates measured in major continental faults using time-lapse satellite interferometry indicate that slow slip events can have a wide range of slip surface areas and durations (Jolivet et al, 2015). Some slow slip events can occur on a fault tens of years after a major earthquake (Aslan et al, 2019). Slow slip events can trigger seismicity (Lohman & McGuire, 2007) and may control the nucleation process before some major earthquakes (Bouchon et al, 2011).…”