بررسی زمان وقوع زلزله به کمک تحلیل زمان طبیعی برای زلزله‌ی 5/5 ریشتری جمهوری آذربایجان

زلزله به عنوان یکی از بلایای طبیعی، از نظر جانی و مالی همواره خطری برای جوامع بشری محسوب می‌شود؛ به همین دلیل، تلاش برای پیش‌بینی زلزله به عنوان یکی از راه‌کارهای مقابله با زلزله همواره مورد توجه بوده است. از طرفی کشور ایران با قرارگیری در کمربند کوهزایی آلپ هیمالیا که یکی از لرزه‌خیزترین مناطق جهان است، از نظر لرزه‌خیزی در وضعیت لرزه خیزی شدید قرار دارد. یکی از موفق‌ترین پیش‌نشانگرهای کوتاهمدت زلزله، سیگنال‌های الکتریکی لرزه‌ای (ses) است که روش van نامیده شده است. در این ارتباط از اوایل سال 1393 ایستگاه‌هایی جهت ثبت و پایش سیگنال‌های الکتریکی لرزه‌ای در شمال‌غرب ایران نصب گردیده است. با دریافت و تحلیل این سیگنال‌ها، می‌توان بزرگا، رومرکز و زمان زلزله‌ی قریب‌الوقوع را تعیین کرد. این پژوهش به بررسی ses دریافت شده در تاریخ 16 مرداد 1394 و چگونگی انجام تحلیل‌های زمان طبیعی جهت پی بردن به زمان وقوع زلزله‌ی پیش رو در بازه‌ی زمانی کمتر از یک هفته می‌پردازد. نتایج تحلیل‌های زمان طبیعی نشان داد که این سامانه در تاریخ 12 شهریور 1394 به مرحله‌ی بحرانی رسیده است و متعاقباً در صبح 13 شهریور 1394 زلزله‌ی اصلی این سامانه به بزرگای 5.5 ریشتر در منطقه‌ی ائقوز جمهوری آذربایجان و در فاصله‌ی 310 کیلومتری از ایستگاه اسپیران به وقوع پیوست. نکته‌ی مهم در این رابطه این است که در فاصله‌ی زمانی 6 ماه پیش و 6 ماه پس از این زلزله، هیچ زلزله‌ی بزرگتر از 5 ریشتری در منطقه مورد مطالعه رخ نداده است؛ که خود تاییدی بر اتفاقی نبودن این پیش‌بینی است.

Investigation of the time occurrence of Azerbaijan earthquake M=5.5 by natural time analysis

IntroductionEarthquakes as natural disasters, are always considered to be a risk for human societies in terms of economy and life. Therefore, attempts to predict earthquakes have always been considered as a way of risk management. On the other hand, Iran is located in a critical seismic condition through the AlpineHimalayan orogenic belt, which is one of the most seismic areas in the world. Talesh Mountains are located in North West of Iran, in the south of the Caucasus orogeny, east of the Anatoly, and north of the Zagros orogeny. Many minor and major earthquake faults such as Tabriz fault, North Anatoli fault, East Anatoli fault, Zagros main fault and Alborz Western faults are effective in this area.Materials and methodsEarthquake prediction by electric precursors, known as VAN method, is one of the most successful shortterm methods of earthquake prediction. This method (VAN) is based on researching the changes in Geoelectric potentials, called seismicelectric signals (SES) which can be detected before earthquakes. SES could be shown in special locations (sensitive sites) and sensitive sites receive the SES as a selection from the seismic sources. Therefore, it is possible to estimate the location of the event up to 100 Kms far away. The magnitude of the progressive earthquake could be forecasted up to 0.7unit tolerance in Richter scale. Professor Vrotsos that is the founder of the VAN method and director of the solid state physics in University of Athens has published more than 250 papers and 8 books in this subject. In the last two decades the VAN team developed the time series analysis to forecast earthquakes, called “Natural time analysis”. In this paper, according to this method, the occurrence of one earthquake M=5.5 is analyzed. Results and discussionSince 2014 a network of VAN stations were installed in NW Iran for recording and monitoring the Seismic Electric Signals (SES). Receiving and analyzing these signals, could help determine the magnitude, epicenter and time of impending earthquakes. This research investigates an SES received on 7th of August 2015 and application of natural time analysis to find out the time occurrence of the subsequent impending earthquake, in a time window less than a week. The natural time analysis indicates that this system reached the critical point, on September 3rd 2015 and subsequently on 4th of September 2015 the 5.5 Richter (MN) main shock occurred in Oghuz municipality in the Republic of Azerbaijan, at a distance of 310 km from Ispiran station. The important point is that this earthquake is the only earthquake greater than 5 Richter occurring in the study area in 6 months before and after this event. This confirms that this prediction wasn’t random.ConclusionSince 2014 a network of VAN stations were installed in NW Iran for recording and monitoring the Seismic Electric Signals (SES). Receiving and analyzing one of the signals, helped determine the magnitude, epicenter and time of impending earthquakes. This research investigates an SES received on 7 August 2015 and how to apply the natural time analysis to find out the occurrence of the subsequent impending earthquake, in a time window less than a week. The natural time analysis indicates that this system reached the critical point, on 3 September 2015 and subsequently On 4 September 2015 the 5.5 Richter (MN) main shock occurred in Oghuz municipality in the Republic of Azerbaijan, at a distance of 310 km from Ispiran station.