The 30 October 2020 Samos earthquake (Mw 7.0) ruptured an east–west striking, north dipping normal fault located offshore the northern coast of Samos Island, previously inferred from the bathymetry ...and regional tectonics. This fault, reported in the fault-databases as the
North Samos
and/or
Kaystrios Fault
, ruptured with almost pure dip-slip motion, in a region where both active extension and strike-slip deformation coexist. Historical information for the area confirms that similar ~ Mw7 events had also occurred in the broader Samos area, though none of the recent (last ~ 300 years) mainshocks appears to have ruptured the same fault. The spatial and temporal distribution of relocated aftershocks indicates triggering of nearby strike-slip and normal fault segments, situated in the areas where static stress has increased due to the mainshock generation. The relocated aftershocks and the slip model indicate that the sequence ruptured the upper crust (mainly the depth range 3–15 km). The top of the rupture plane nearly reached the sea bottom, located at a depth of < 1 km. Slip is confined in mainly two asperities, both located up-dip from the hypocenter and at shallow depths. The average displacement is ~ 1 m and the peak slip is ~ 3.5 m for a shear modulus of 3.2e10 N/m
2
. While it is difficult to constrain the rupture velocity in the inversions, the model suggests a slow rupture speed of the order of 2.2 km/s. The resolved source duration is ~ 16 s, compatible with the ~ 32 km length of the fault that ruptured.
We present a dataset of 77 strong ground motion records within 200 km epicentral distance from the 30 October 2020, M7.0 Samos Island (Aegean Sea) earthquake, which affected Greece and Turkey. ...Accelerograms from National Networks of both countries have been merged into a single dataset, including metadata that have been uniformly derived using a common preliminary source model. Initial findings from the analysis and comparative examination of acceleration time histories, Fourier amplitude spectra and 5%-damped response spectra are discussed along with significant source, propagation path and site effects. The long-period amplifications observed in most records in Izmir bay triggered failures and severe damages in weak structures. Yet, the spectral accelerations are observed to lie below the current and previous design spectra corresponding to the damaged regions. Peak ground motions are used to construct a purely instrumental-based macroseismic intensity map, which is capable of reflecting the actual earthquake damage caused by this considerably large event. Finally, peak ground motions are compared to various ground motion models (GMMs) and deviations are highlighted. Our overall preliminary analysis reveals a strong energy signature of the Samos earthquake in the period range 0.5–1.5 s at many sites, both on rock and soil, whereas records in the heavily hit Izmir city, at an epicentral distance circa 70 km, provide strong indication for additional amplification due to basin effects. At relatively large distance from the earthquake source (> 120 km), several recorded amplitudes are significantly lower than those predicted by many GMMs, implying that further studies are necessary toward the improvement of regional attenuation models.
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•Simulations indicate a possible advance in the failure time of the Main Marmara Fault’s locked segment.•Dynamic triggering effects can increase the clock advance up to 1% of its ...recurrence time depending on the onset time.•Strong brittle-ductile coupling, smaller asperity size, and reduced clamping shorten the seismic cycle.
The Mw5.8 earthquake in the Marmara Sea west of the locked segment of the North Anatolian Fault sparked a debate on whether this event may trigger or advance the expected large (Mw>7) earthquake close to Istanbul in time. Its potential effect on the major earthquake cycle is analyzed using rate-and-state friction (RSF) dependent spring-slider models by considering miscellaneous views of friction and different simulation strategies. Dynamic and static effects are simulated using recorded seismic waveforms and computed static stress change. Results indicated that this moderate earthquake cannot produce instant triggering on the locked fault segment but can advance the failure time noticeably. Simulations display no sensitivity to the inertial damping term; thus, quasi-dynamic and full-dynamic approaches agree. On the other hand, strong brittle-ductile coupling, smaller asperity size, and reduced clamping due to normal stress variations shorten the seismic cycle and increase the induced failure time advances. If failure is far in time (>5% of the recurrence time), the long-term effect on the seismic cycle is static and especially exceeds Coulomb failure predictions considerably when the system is strongly coupled. If fault failure is close, which is likely in this case, dynamic effects lead to responses that differ among state laws. The Ruina (slip) law which has a weakening rate more consistent with the laboratory velocity step tests, shows the highest failure time advance (≈ 1% of the recurrence interval), implying that the failure time is more imminent than before for the locked fault segment beneath the Marmara Sea.
The 2020 M7.0 Samos earthquake had occurred on the north of Samos Island; however, structural damage was observed in İzmir-Bayraklı, which is located approximately 65 km away from the epicenter. ...Strong ground motions recorded in İzmir Bay showed unique site amplifications, mostly due to the interaction between the basin and deep alluvial deposit response. The objective of this study is to evaluate the predictive performance of current ground motion models (GMMs) for estimating the recorded strong motions, especially the recordings over or near the Bayraklı-Bornova basin. 66 strong motion stations from Turkey with rupture distance (RRUP) < 200 km are used in the residual analysis, considering the ambiguities in the magnitude and depth to the top of the rupture estimations. Event terms of the earthquake for tested GMMs are found to be small and lie within the expected scatter, except for T = 0.5–1.5 s spectral accelerations. Event-specific distance attenuation for RRUP<100 km is consistent with the median predictions of current GMMs; however, the distance scaling for 100 km<RRUP<200 km are significantly different at high frequencies, indicating faster attenuation for Southwestern Anatolia. Relatively long period (0.5–1.5 s) spectral energy is present in both soft sites on the Bayraklı-Bornova basin and rock/stiff-soil sites on the basin edge and these stations contribute significantly to the positive event terms at T = 0.5–1.5 s. For sites within the basin or close to the basin edge, factors such as the direction of the rupture front, basin width and depth, and the seismic structure of the basin contribute to the ground motion variability.
•The structural damage from 2020 Samos Eq. was observed in İzmir-Bayraklı, which is located 65 km away from the epicentre.•The event terms of the earthquake are found to be small, except for T=1 sec, based on the analysis of 66 stations from AFAD.•Distance scaling at high frequencies indicates faster attenuation when compared to current GMMs for large distances.•Mid-period (0.5-1.5 sec) spectral energy is present in soft sites over the İzmir basin and rock sites on the basin edge.•For sites within the basin or close to the basin edge, the variability in recorded ground motions is significant.
Evaluating the distribution patterns of surface temperature data at Very Long Baseline Interferometry (VLBI)/Global Positioning System (GPS) co-located sites w.r.t. normality is one of the most ...important issues in modeling surface temperature data over long periods. Such evaluation can generate algorithms for filling in missing data at measurement sites. Some algorithms in the literature, such as those in the study of Cho et al. J Coast Res 65. doi: 10. 2112/SI65-321. 1, (
2013
), require trend, harmonic, and residual components to fill in the missing data. Trend and harmonic components estimate an optimal model that can be used to assist such algorithms when filling in missing data. The present study is based on the investigation of the normal distribution of the residuals of a surface temperature time series at VLBI/GPS co-located sites, after removing the trend and seasonal effects through harmonic components (inter-daily variations). This study uses surface temperature data collected from the VLBI/GPS co-located sites of two different regions in Europe: Matera (Italy) and Wettzell (Germany). The data collected from these sites form a time series, and time series analyses and conventional
k-sigma
outlier detection are implemented on these data sets before subjecting them to goodness of fit tests for normality. The residual components of the time series are acquired through a decomposing trend and signal effect from the original time series, assuming that the residuals of the time series are normally distributed. In testing the hypothesis that an observed frequency distribution fits the normal distribution, the following tests are used: Pearson
χ
2
, Kolmogorov-Smirnov, Anderson-Darling, Shapiro-Wilk or Shapiro-Francia, D’Agostino, Jarque-Bera, skewness, and kurtosis tests. Some graphical methods are also applied to support the results of the goodness of fit tests for normality. Some proposals on the application of the goodness of fit tests are put forward, such as the evaluation of the estimation model for trend and harmonic components by considering the properties of the implemented goodness of fit tests. The results of this study can be used to determine the optimal model for estimating trend and harmonic components. The output of the present study is expected to have an important role in modeling surface temperature distributions at co-located VLBI/GPS sites for filling in missing data. Above all, meteorological data, such as temperature, pressure, and humidity, are of specific interest for modeling tropospheric delay, the main error factor in positioning in space geodesy, which in turn makes investigations on the distribution of meteorological data more attractive in geoscience.
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