Browsing by Subject "Earthquakes"

Now showing 1 - 11 of 11

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Deprem
(1968) Uygur, Nermi
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Dere tepe deprem
(1999) Duru, Orhan
Open Access
Financial earthquakes, aftershocks and scaling in emerging stock markets
(Elsevier BV, 2004) Selçuk, F.
This paper provides evidence for scaling laws in emerging stock markets. Estimated parameters using different definitions of volatility show that the empirical scaling law in every stock market is a power law. This power law holds from 2 to 240 business days (almost 1 year). The scaling parameter in these economies changes after a change in the definition of volatility. This finding indicates that the stock returns may have a multifractal nature. Another scaling property of stock returns is examined by relating the time after a main shock to the number of aftershocks per unit time. The empirical findings show that after a major fall in the stock returns, the stock market volatility above a certain threshold shows a power law decay, described by Omori's law. © 2003 Elsevier B.V. All rights reserved.
Open Access
Investigation of hourly and daily patterns for lithosphere-ionosphere coupling before strong earthquakes
(IEEE, 2009-06) Karatay, S.; Arıkan F.; Arıkan, Orhan
The ionosphere can be characterized with its electron density distribution which is a complex function of spatial and temporal variations, geomagnetic, solar and seismic activity. An important measurable quantity about the electron density is the Total Electron Content (TEC) which is proportional to the total number of electrons on a line crossing the atmosphere. TEC measurements enable monitoring variations in the space weather. Global Positioning System (GPS) and the network of world-wide receivers provide a cost-effective solution in estimating TEC over a significant proportion of global land mass. In this study, five earthquakes between 2003-2008 that occurred in Japan with different seismic properties, and the China earthquake in May 2008 are investigated. The TEC data set is investigated by using the Kullback-Leibler Divergence (KLI), Kullback-Leibler Distance (KLD) and L2-Norm (L2N) which are used for the first time in the literature in this context and Cross Correlation Function (CCF) which is used in the literature before for quiet day period (QDP), disturbed day period (DDP), periods of 15 days before a strong earthquake (BE) and after the earthquake (AE). In summary, it is observed that the CCF, KLD and L2N between the neighbouring GPS stations cannot be used as a definitive earthquake precursor due to the complicated nature of earthquakes and various uncontrolled parameters that effect the behavior of TEC such as distance to the earthquake epicenter, distance between the stations, depth of the earthquake, strength of the earthquake and tectonic structure of the earthquake. KLD, KLI and L2N are used for the first time in literature for the investigation of earthquake precursor for the first time in literature and the extensive study results indicate that for more reliable estimates further space-time TEC analysis is necessary over a denser GPS network in the earthquake zones. ©2009 IEEE.
Open Access
Investigation of litosphere-ionosphere coupling using total electron content
(IEEE, 2009) Karatay, S.; Arıkan, F.; Arıkan, Orhan
In this study, the relation between Total Electron Content (TEC) estimates obtained from GPS and the earthquakes is examined. Five earthquakes between 2003-2008 occured in Japan with different properties and China earthquake in May 2008 are chosen for the purpose. The 15-days period before and after the registered earthquakes are considered for the basis of this investigation. Also the TEC in computed for each GPS station for the time periods including Ionosphere quiet and disturbed days not without any serious earthquake in the region. For the statistical analysis, the cross correlation function (CC) which is used in the literature before, and the Kullback-Leibler Divergence (KLD) with L2-Norm (L2N) methods which are used for the first time in this context, are applied to the data sets. The computed values for CC, KLD and L2N are compared for both between different GPS stations where available and between consecutive days for the time periods in the data set. With CC analysis, the anomalies existed in the earthquake time intervals are also observed for the quiet days data set. For the earthquakes with scale larger than 6, the possibilities of generating an alarm signal is more likely with a future detailed comperative study of the estimated TEC nearby GPS station estimates in space and time.
Open Access
Investigation of total electron content variability due to seismic and geomagnetic disturbances in the ionosphere
(Wiley-Blackwell Publishing, 2010-10-20) Karatay S.; Arikan, F.; Arıkan, Orhan
Variations in solar, geomagnetic, and seismic activity can cause deviations in the ionospheric plasma that can be detected as disturbances in both natural and man-made signals. Total electron content (TEC) is an efficient means for investigating the structure of the ionosphere by making use of GPS receivers. In this study, TEC data obtained for eight GPS stations are compared with each other using the cross-correlation coefficient (CC), symmetric Kullback-Leibler distance (KLD), and L2 norm (L2N) for quiet days of the ionosphere, during severe geomagnetic storms and strong earthquakes. It is observed that only KLD and L2N can differentiate the seismic activity from the geomagnetic disturbance and quiet ionosphere if the stations are in a radius of 340 km. When TEC for each station is compared with an average quiet day TEC for all periods using CC, KLD, and L2N, it is observed that, again, only KLD and L2N can distinguish the approaching seismicity for stations that are within 150 km radius to the epicenter. When the TEC of consecutive days for each station and for all periods are compared, it is observed that CC, KLD, and L2N methods are all successful in distinguishing the geomagnetic disturbances. Using sliding-window statistical analysis, moving averages of daily TEC with estimated variance bounds are also obtained for all stations and for all days of interest. When these bounds are compared with each other for all periods, it is observed that CC, KLD, and L2N are successful tools for detecting ionospheric disturbances.
Open Access
İyonküre elektron içeriği kullanılarak deprem öncül tespit sinyali oluşturulması
(IEEE, 2014-04) Akyol, Ali Alp; Arıkan, Orhan; Arıkan, F.
Sismik olayların iyonküredeki elektron dağılımını etkilediği ve bu etkinin bir kaynağının sismik hareketlilik öncesi kayaçların sıkışması sonucu kayaç yüzeylerinde oluşan elektrik alanın yol açtığı iyonlaşma olduğu yakın zamanda yapılan deneyler ile gösterilmiştir. Sismik olayların yol açtığı bu tür bir etkinin iyonkürenin dinamik yapısı içinde güvenilir şekilde tespit edilebilmesi depremlerin erken tahminini sağlayabilecek önemdedir. Bu çalışmada bir YKS alıcı ağından düzenli olarak elde edilen Toplam Elektron İçeriği (TEİ) ölçümleri kullanılarak iyonküredeki yerel değişimlerin tespit edilmesine yönelik bir teknik geliştirilmiş ve bu tekniğin güvenilir bir deprem öncül sinyali üretip üretemediği 2010 ve 2011 yıllarını kapsayan bir zaman aralığında test edilmiştir. Geliştirilen deprem öncül tespiti tekniğinin bu tarih aralığında Türkiye’de Richter ölçeğinde 5 ve üzeri büyüklükte meydana gelen 23 depremin 15’ini tespit edebildiği ve 8 yanlış alarm verdiği gözlemlenmiştir.
Open Access
Locating temporary shelter areas after an earthquake: a case for Turkey
(Elsevier, 2015) Kılcı, F.; Kara, B. Y.; Bozkaya, B.
In this study, we propose a mixed integer linear programming based methodology for selecting the location of temporary shelter sites. The mathematical model maximizes the minimum weight of open shelter areas while deciding on the location of shelter areas, the assigned population points to each open shelter area and controls the utilization of open shelter areas. We validate the mathematical model by generating a base case scenario using real data for Kartal, Istanbul, Turkey. Also, we perform a sensitivity analysis on the parameters of the mentioned mathematical model and discuss our findings. Lastly, we perform a case study using the data from the 2011 Van earthquake.
Open Access
Observed Ionospheric Effects of 23 October 2011 Van, Turkey Earthquake
(Taylor and Francis, 2012-01-17) Arikan, F.; Deviren, M.N.; Lenk, O.; Sezen, U.; Arıkan, Orhan
On 23 October 2011, a very strong earthquake with a magnitude of Mw = 7.2 shook Eastern Anatolia, and tremors were felt up to 500 km from the epicentre. In this study, we present an early analysis of ionospheric disturbance due to this earthquake using Global Positioning Satellite-Total Electron Content (GPS-TEC). The variability with respect to average quiet day TEC (AQDT) and variability between the consecutive days are measured with symmetric Kullback-Leibler divergence (SKLD). A significant variability in total electron content (TEC) is observed from the GPS stations in the 150 km neighbourhood of the epicentre eight and nine days prior to the earthquake. An ionospheric disturbance is observed from GPS stations even more than 1,000 km to the epicentre, especially those on the North Anatolian fault (NAF). The present results support the existence of lithosphere-atmosphere-ionosphere coupling (LAIC) associated with Van, Turkey earthquake. © 2012 Taylor and Francis Group, LLC.
Open Access
A study of lithosphere-ionosphere coupling using TUSAGA active TEC estimates
(IEEE, 2010) Karatay, S.; Arikan F.; Arıkan, Orhan; Sayin I.; Aysezen, M.Ş.; Lenk O.; Aktuǧ, B.
In this study, the disturbances in the ionosphere due to the seismic activity are investigated by using Total Electron Content estimates obtained from TUSAGA Active GPS stations in Turkey. Two earthquakes with same geophysical properties occurred on Northern Anatolia Fault are chosen for the study. TEC estimates are compared with each other using correlation coefficient (IK), symmetric Kullback-Leibler Distance (KLD) and L2-Norm (L2N) for geomagnetically and seismically quiet days of ionosphere and the earthquakes days. It is observed that IK values of quiet days are highly correlated in quiet days. IK values of earthquake days decrease down to 0.2 in earthquake days. KLD values of earthquake days are 10 times greater than those of the quiet days. In order to form a proper earthquake precursor alarm signal, more earthquakes with different properties have to be investigated in the future. ©2010 IEEE.
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Yataktan nasıl düştüm?
(1999) Duru, Orhan