Depremsellik ve deprem tehlikesinin incelenmesi için interaktif bir algoritma geliştirilmesi

Abstract

Bu çalışmada aletsel dönemdeki deprem verileri alınarak bir bölgede deprem etkinliğinin ve deprem tehlikesinin araştırılmasında kolaylık sağlayacak bir bilgisayar programı geliştirilmiştir. Sınırları 39°-4E. 5° kuzey enlemleri ile 36°-31 ° doğu boylamları arasında kalan Marmara Bölgesi örnek seçilerek coğrafik sınırlar, bölgenin Jeolojik ve' tektonik yapısını gösteren haritalar sayısal hale ge tirilmiş ve bu bilgiler haritalanmıştır. Bölgedeki depremlerin episantr dağılım haritası çıkarılmıştır. Seçilen herhangi bir alanda deprem parametreleri nin zaman ve uzaydaki dağılımını ve birbirleriyle olan ilişkilerini gösteren grafiklerin çizilmesi sağlanmıştır. Gumbel uç değerler yöntemi ile bölgeye ilişkin olası sismik tehlike değerleri saptanmış ve sismik tehlike haritası çıkarılmıştır.

The extensive devastations during catastrophic earthquakes require vigorous investigations to reduce losses of life and in economy. Generally, the better the economy and infrastruc ture in countries of high seismic activity is developed the greater the efforts of the society toward earthquake protection vill be. Particular attention should be payed to the asses- ment and mitigation of earthquake risk in earthquake strucken developing countries, where major investments and vital lifeline systems are frequently concentrated in seismically dangerous areas. Especially there the economic losses incured by a devastating earthquake may result in serious economic disruptions with all its detrimental social consequen ces. Therefore, regional as well as detailed urban planning in seismic active areas should rest on proper knowledge of: - Regional geology and tectonics - Regional seismicity, earthquake catalogues - Charasteri sties of regional seismic activity and strong ground motion - Seismic zoning, both on seismological and tectonical data - Faulting and permanent round deformations, land slides, other geological effect of earlier earthquakes - Regional distribution of earthquake effects - Microzoning of special local areas - Engineering aspect of disastrous earthquakes, damage distrubution on different structural types Fault geometry plays an important role in control ling the location of large earthquake rupture segments along the fault zones. Fault geometry not only plays a role in the extent of earthquake rupture but also in charasteristics of earthquake behavior. The earthquakes are not equally distrubuted in space and in time. Therefore, earthquakes can be assumed to be random events. Statistical investigations are an important funda ment for the assesment of seismic hazard. The probabi listic nature of forecasting the size of earthquake occurences such as the expected magnitude, ground acce leration, velocity or displacement, leads seismologists to use statistical models which have proved to be reli yi able decision making tools elsewhere. Several statistical models have been applied to the analysis of earthquake occurence sequences with varying degrees of succes. Generally, the statistical treatment used falls into one or two caiagories; VI a. "Whole process" methods using the whole data set like the Gutenberg-Richter cumulative frequency C Gutenberg and Richter,19443. b. "Part process" methods using part of the data set; like the annual extremes.. ' Advantages and limitations of both methodologies are discussed elsewhere. It has been shown that in terms of evaluating the hazard associated with large damaging earthquakes the models of second category may be appropriate given the available data and earthquake catalogues. Seismicity and seismic hazard mapping in terms of earthquake epicentre and hypocentre distrubution and avarage recurrence intervals of different magnitude le vels are an important aspect of overall seismic hazard analysis. Marmara region is seismically one of the most active region in Turkey. Assesment of seismic hazard for the populated and industrial cities in the Marmara region are important. In this study, a computer program is developed for seismic investigations and hazard analysis in a region. The program is coded in Turbo Pascal S. 5 and has been tested on Personal Computers. It is an interactive program that plots data in geographical coordinates. Geographical grid is constructed in a two step procedure. First, geographical coordinates are transformed to projection coordinates, then scaled to VII display coordinates. It is important that geographical coordinates be used in spatial analysis, because they are absolute and menageable put into maps, at' whatever scale or projec tions. The primary data required is a chronological catalogue of earthquakes. The choronologically ordered earthquake catalogue will contain earthquake dates and epi central parameters in the form of 1 ati dude, longitude and magnitude Cand preferable focal depth km if ground motion hazard analysis is to be performed}. First, the program extract all earthquakes from the catalogue which have occured in the chosen area, secondly, it is drawing geographic map. The program makes extensive use of windows and menus. The results are presented in the form of graphics. The result can be overlayed to other drawing. The primary earthquake data is used here including eathquakes between 1QOO-1987 years in Turkey. The epi- central distrubution of the catalogued earthquakes is drawn by to use the program. Epicentre maps including also magnitude knowledges. * Alternative statistics of seismicity are applied to the catalogue. The whole process of seismicity occurence is analysed, using the common Guten£erg-Ri enter cumulative frequency equation and part process results obtained by Gumbel extrem value analysis. vTII The distrubution of seismic hazard in terms of maximum expected magnitudes and ground acceleration are shown in the form of graphics.