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  • 1
    Publication Date: 2020-10-01
    Description: Predictive relationships for the ground motion in the Marmara region (northwestern Turkey) are parametrized after regressing three-component waveforms from regional earthquakes, in the frequency range: 0.4–15.0 Hz, and in the distance range: 10–200 km. The data set consists of 2400 three-component recordings from 462 earthquakes, recorded at 53 stations. Moment magnitudes, Mw, range between 2.5 and 7.2. The largest event for which we have waveforms available (Mw 7.2) occurred in Duzce on 1999 November 12. The aftershocks of that earthquake, together with the aftershocks of the 1999 August 17 Izmit event (Mw = 7.4), are included in the dataset. Regressions are performed, independently, on Fourier velocity spectra and on peak ground velocities, for a large number of sampling frequencies. A simple model is used to relate the logarithm of the measured ground motion to excitation, site, and propagation terms. Results obtained for peak velocities are used to define a piecewise continuous geometrical spreading function, g(r), a frequency-dependent Q(f ), and a distance-dependent duration function. The latter is used, through random vibration theory (RVT), in order to predict time-domain characteristics (i.e. peak values) of the ground motion. The complete model obtained for the peak ground motion was used to match the results of the regressions on the Fourier amplitudes. Fourier velocity spectra for the combined horizontal motion are best fit by a hinged quadrilinear geometrical spreading function for observations in the 10–200 km hypocentral distance ranges as a function of frequency: f 〈 1.0 Hz, r−1.2 for r ≤ 30 km; r−0.7 for 30 〈 r ≤ 60 km; r−1.4 for 60〈r ≤100 km; r−0.1 for r 〉100, f ≥1.0 Hz, r−1.0 for r ≤30 km; r−0.6 for 30〈r ≤ 60 km; r−0.9 for 60〈r ≤100 km; r−0.1 for r 〉100 km. The frequency-dependent crustal shearwave quality factor Q (f ) coefficient Q( f )=180 f 0.45. The T (5–75 per cent) duration window provides good agreement between observed and predicted peak values. By modelling the behaviour of the small earthquakes at high frequency, we also quantified a regional parameter κ = 0.055 s. Spectral models with one single-corner frequency (Brune), and with two-corner frequencies (Atkinson and Silva) fit the observed high-frequency excitation levels equallywell, whereas the model by Atkinson and Silva fits the low-frequency observations slightly better than Brune’s. RVT is used to predict the absolute levels of ground shaking, following Boore’s implementation of the stochastic ground motion model (Boore’s SMSIM codes). Our regional empirical predictive relationships are compared to the ones adopted in several regions of the world, from California to Western United States.
    Description: Published
    Description: 635-651
    Description: JCR Journal
    Description: reserved
    Keywords: attenuation ; ground motion scaling ; ground motion scaling ; Turkey ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 250 (1996), S. 750-760 
    ISSN: 1617-4623
    Keywords: Key words lys3a ; CpG island ; Transient expression ; Particle bombardment ; Immunocytochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  B- and C-hordein gene transcription is severely reduced in the endosperm of the regulatory barley mutant lys3a, and this is correlated with persistent hypermethylation of the promoters. In contrast, D-hordein is expressed at normal levels in the mutant. To confirm the connection between methylation and transcriptional activity, a genomic D-hordein clone was isolated and sequenced. The nucleotide composition of the promoter region revealed a CpG island and methylation analysis, using bisulphite treatment of genomic DNA, confirmed that the D-hordein promoter is unmethylated in endosperm and leaf tissue. Immunocytochemical studies localized D-hordein to the reticular component of protein bodies in both the wild-type Bomi and lys3a. Transient expression of GUS reporter gene constructs in barley endosperm, following transfection by particle bombardment revealed the D-hordein promoter to be 3–5 fold more active than B- or C-hordein promoters. Comparison of transient expression in Bomi and lys3a endosperm demonstrated that the activities of the unmethylated D-hordein and the Hor1-14 C-hordein promoters were equivalent, while the activities in the mutant of the Hor1-17 C-hordein and the Hor2-4 B-hordein promoters were reduced two- and tenfold, respectively. Methylation of plasmids in vitro prior to expression severely inhibited B- and D-hordein promoter activities. Based on these observations two categories of promoters for endosperm-specific expression of storage proteins are recognized and a model involving methylation and modulation of chromatin structure in the regulation by the Lys3 gene is presented.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 1992-05-01
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2015-10-22
    Description: The Shanxi rift system is one of the most active intraplate tectonic zones in the North China Block, resulting in devastating seismicity. Since 1303, the rift has experienced fifteen M s ≥ 6.5 earthquakes. Aiming at a better understanding of Coulomb stress evolution and its relationship with the seismicity in the rift system, we investigated the Coulomb stress changes due to coseismic slip and post-seismic relaxation processes following strong earthquakes as well as the interseismic tectonic loading since the 1303 Hongdong M s = 8.0 earthquake. Our calculation applies a specified regional medium model, takes the gravity effect into account and uses the fault geometry of the next event as the receiver fault in a given calculation. Our results show that nine out of 12 M s ≥ 6.5 earthquakes since the 1303 Hongdong earthquake and more than 82 per cent of small-medium instrumental events after the 1989 Datong-Yanggao M s = 6.1 earthquake fall into the total stress increased areas. Our results also reveal the different roles of the coseismic, post-seismic and interseismic Coulomb stress changes in the earthquake triggering process in the Shanxi rift system. In a short period after a strong event, the stress field changes are dominated by coseismic Coulomb stress due to sudden slip of the ruptured fault, while in the long term, the stress field is mainly dominated by the accumulation of interseismic tectonic loading. Post-seismic stress changes play an important role by further modifying the distribution of stress and therefore cannot be ignored. Based on the current stress status in the Shanxi rift system, the Linfen basin, southern and northern Taiyuan basin, Xinding basin and the north part of the rift system are identified as the most likely locations of large events in the future. The results of this study can provide important clues for the further understanding of seismic hazard in the Shanxi rift system and thus help guiding earthquake risk mitigation efforts in the future.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 5
    Publication Date: 2016-06-10
    Description: Published results of coda Q show a large variation in values. These variations are often claimed to be related to different tectonics, whereas they might just be related to using different assumptions in the processing, leading to different input parameters for the analysis. In this study, the effect of using different processing parameters is investigated and significant differences, particularly at low frequencies, are observed. We find a new set of optimal parameters, which we recommend using in future studies. Using a short lapse time of 30 s and optimal parameters, data from both similar and very different tectonic regions are used to calculate coda Q using the same program and the same parameters. The regions considered are eastern Anatolia, the Azores, Jan Mayen, northwestern and central Argentina, the Shanxi rift system in China, and southwestern Norway. We obtain the following relations: eastern Anatolia ( Q =88 f 0.66 ), Azores ( Q =86 f 0.70 ), Jan Mayen ( Q =90 f 0.72 ), northwestern and central Argentina ( Q =89 f 0.94 ), Shanxi rift system ( Q =99 f 0.89 ), and southwestern Norway ( Q =124 f 0.91 ). The results show that coda Q is very similar for regions of similar tectonics and significantly different for regions with varying tectonics. Using alternative, more common parameters gives different Q , but the regional differences remain, so which parameters to use to get correct coda Q values is still uncertain. However, coda Q can clearly distinguish different tectonic areas provided identical processing parameters are used, even if they are not optimal.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 6
    Publication Date: 2015-03-07
    Description: Earthquake focal mechanisms of the Shanxi rift system, North China, are investigated for the time period 1965–April 2014. A total of 143 focal mechanisms of M L ≥ 3.0 earthquakes were compiled. Among them, 105 solutions are newly determined in this study by combining the P -wave first motions and full waveform inversion, and 38 solutions are from available published data. Stress tensor inversion was then performed based on the new database. The results show that most solutions in the Shanxi rift system exhibit normal or strike-slip faulting, and the regional stress field is transtensional and dominated by NNW–SSE extension. This correlates well with results from GPS data, geological field observations and levelling measurements across the faults. Heterogeneity exists in the regional stress field, as indicated by individual stress tensor inversions conducted for five subzones. While the minimum stress axis ( 3 ) appears to be consistent and stable, the orientations, especially the plunges, of the maximum and intermediate stresses ( 1 and 2 ) vary significantly along the strike of the different subzones. Based on our results and combining multidisciplinary observations from geological surveys, GPS and cross-fault monitoring, a kinematic model is proposed for the Shanxi rift system, in which the rift is situated between two opposite rotating crustal blocks, exhibiting a transtensional stress regimes. This model illustrates the present-day stress field and its correlation to the regional tectonics, as well as the current crustal deformation of the Shanxi rift system. Results obtained in this study, may help to understand the geodynamics, neotectonic activity, active seismicity and potential seismic hazard in this region.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 7
    Publication Date: 2006-08-01
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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  • 8
    Publication Date: 2007-06-01
    Description: Jan Mayen is an active volcanic island situated along the mid-Atlantic Ridge north of Iceland. It is closely connected with the geodynamic processes associated with the interaction between the Jan Mayen Fracture Zone (JMFZ) and the slowly spreading Kolbeinsey and Mohns Ridges. Despite the significant tectonic activity expressed by the frequent occurrence of medium to large earthquakes, detailed correlation between individual events and the causative faults along the JMFZ has been lacking. Recently acquired detailed bathymetric data in the vicinity of Jan Mayen has allowed us to document such correlation for the first time. The earthquake of 14 April 2004 (M (sub w) 6), which occurred along the JMFZ, was studied in detail and correlated with the bathymetry. Locations of aftershocks within the first 12 hours after the mainshock outline a 10-km-long fault plane. Interactions between various fault systems are demonstrated through locations of later aftershocks, which indicate that supposedly normal fault structures to the north of the ruptured fault, in the Jan Mayen Platform, have been reactivated. Correlation of the waveforms shows that events located on these structures are significantly different from activity at neighboring structures. Coulomb stress modeling gives an explanation to the locations of the aftershocks but cannot reveal any information about their mechanisms.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 9
    Publication Date: 2007-06-01
    Description: Following the disastrous earthquakes in Izmit and Duzce along the North Anatolian fault in 1999, the earthquake hazard in the Istanbul area became a great concern. In this study we simulate strong ground motions caused by a scenario earthquake (M 7.5) in the Marmara Sea, and investigate the effect of varying the input parameters on the broadband frequency ground motion. Simulations are based on a multiasperity source model that involves the combined rupture of the North Anatolian fault segments beneath the Marmara Sea. We use a hybrid model combining a deterministic simulation of the low frequencies (0.1-1.0 Hz) with a semistochastic simulation of the high frequencies (1.0-10.0 Hz). Computation at each frequency range is performed separately and the total ground motion is combined in the time domain. Computations are linear and are performed at bedrock level, thereby not taking any effect of local geological conditions into account. We calculate a total of 17 earthquake scenarios corresponding to different source and attenuation parameters to study their effect on the ground motion. The most significant parameters in terms of ground-shaking level are the rise time, rupture velocity, rupture initiation point, and stress drop. The largest variability of strong ground motions is observed in regions adjacent to asperities and is associated with frequencies higher than 5 Hz. For lower frequencies our simulated velocity spectra within the Istanbul area are fairly stable among scenarios. The average standard deviations of all ground-motion measures are less than 35% of the mean.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 10
    Publication Date: 2007-01-01
    Description: On 26 December 2004, a devastating earthquake of M 9.3 occurred offshore northern Sumatra. Due to the size of this earthquake and the accompanying tsunami wave, disastrous consequences have been observed in several countries around the Indian Ocean. The tectonics in the region are characterized by the oblique, north-northeast-oriented subduction of the Indian-Australian plate under the Sunda microplate with a rate of 6-6.5 cm/yr. This oblique convergence results in strain partitioning, where the trench-perpendicular thrust faulting along the subducting slab accommodates the east-west component of the motion, whereas the north-south component of the motion is probably accommodated by the right-lateral strike-slip faulting along the Great Sumatran fault and the Mentawi fault. Source parameters of the 26 December 2004 event have been used for modeling the resulting ground motions in the nearby affected regions. Results give an insight on the importance of ground shaking in the total destruction of places like Banda Aceh, northern Sumatra, Indonesia. The modeling is performed for a multiasperity finite fault using a hybrid procedure combining deterministic modeling at low frequencies and semistochastic modeling at high frequencies. Results show that strong shaking was distributed over a large area including northwestern Sumatra and its offshore islands. In Banda Aceh, which experienced significant damage, bedrock velocities reached 60 cm/sec with duration of the shaking of ca. 150 sec. The largest ground motions occurred near the strongest asperities of the fault plane, where velocities of 200 cm/sec are modeled for bedrock conditions.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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