محاسبه پارامترهای چشمه و جنبش نیرومند زمین در زمین‌لرزه 21 آبان 1396 سرپل ذهاب، کرمانشاه، با استفاده از شتاب‌نگاشت‌های شبکه شتاب‌نگاری زلزله ایران

نوع مقاله: مقاله تحقیقی‌ (پژوهشی‌)

نویسندگان

شبکه شتابنگاری زلزله ایران، مرکز تحقیقات راه، مسکن و شهرسازی، تهران، ایران

چکیده

در تاریخ 21/08/1396 زمین‌لرزه بزرگی با بزرگای محلی 3/7Mn در نزدیکی ازگله- سرپل ذهاب در استان کرمانشاه روی داد. این زمین‌لرزه را 113 ایستگاه شتاب‌نگاری شبکه شتاب‌نگاری زلزله ایران (ISMN) ثبت کردند. در این تحقیق با استفاده از داده­های شتاب‌نگاری، پارامترهای چشمه زمین‌لرزه از جمله گشتاور لرزه‌ای (M0)، بزرگای گشتاوری زلزله (M) و فرکانس گوشه (fc) محاسبه شده است. این پارامترها با استفاده از روش اندروز (1986) و روش وارون­سازی طیف جابه‌جایی بر اساس مدل چشمه برون در حوزه فرکانس تعیین شده‌اند. همچنین ضریب کیفیت مستقل از فرکانس (Q)، شعاع چشمه فرضی دایره‌ای (r) و میزان افت تنش (∆σ) در این زمین‌لرزه نیز تعیین شده است. برای محاسبه پارامترهای چشمه از دو پنجره زمانی موج S و کل نگاشت استفاده شده است. مقادیر به‌دست‌آمده برای بزرگای گشتاوری 3/7 و 4/7 است که همخوانی بسیار خوبی با مقادیر گزارش­شده از طرف مراکز معتبر بین‌المللی نشان می­دهد. علاوه­بر پارامترهای چشمه، پارامترهای جنبش نیرومند زمین نیز بررسی و مقادیر بیشینه شتاب، سرعت، جابه‌جایی و طیف پاسخ این زمین‌لرزه محاسبه و ارائه شده است. مقایسه مقادیر مشاهده­شده شتاب و سرعت با روابط تخمین پارامترهای جنبش شدید زمین بور و همکاران (2014)، حاکی از مناسب بودن این روابط برای منطقه مورد نظر با درنظرگرفتن بزرگای این رویداد است. 

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Source and Strong Ground Motion Parameters Estimation of the November 12, 2017, Sarpol-e Zahab, Kermanshah Earthquake Using Recorded Accelerograms of Iran Earthquake Strong Motion Network

نویسندگان [English]

  • Attieh Eshaghi
  • Mohammad Pour-Mohammad Shahvar
  • Esmaeil Farzanegan
  • Hossein Mirzaei Alavijeh
Road, Housing & Urban Development Research Center, Tehran, Iran
چکیده [English]

On Sunday, November 12, 2017, a strong earthquake with local magnitude of Mn7.3 occurred in the border region between Iran and Iraq in vicinity of the Sarpol-e Zahab town. Unfortunately, this catastrophic event caused many causalities, thousands of injured and vast amounts of damage to the buildings, houses and infrastructures in the epicentral area. The earthquake epicenter was located about 10 km south of Ezgeleh in the Zagros seismotectonic zone. This earthquake was recorded by 113 stations of Iran Strong Motion Network (ISMN) across the country. The nearest station to the epicenter of the earthquake was Sarpol-e Zahab (SPZ) station at a distance of about 39 km. In this research, the source parameters of the earthquake including the seismic moment (M0), the moment magnitude (M) and the corner frequency (fc) were estimated using two methods of Andrews (1986) and inversion of the displacement spectra based on the Brune source model in the frequency domain using ISMN strong motion data. Additionally, the frequency independent quality factor (Q), the source radius (r) (considering a hypothetical circular source), and the stress drop of the earthquake (∆σ) were calculated. The above mentioned values were calculated based on two time windows: the S-wave window and the whole trace window for both methods. The moment magnitude of the event is M7.4 based on the displacement spectra inversion for the whole trace window and M7.3 based on the S-wave window. The estimated value for both windows using the Andrews (1986) methodis M7.3. The estimated M values are in excellent agreement with the reported values. The calculated corner frequencies are from 0.13 to 0.17 Hz and the estimated source radii of the event using both methods are in the 9-11.5 km range. Moreover, the estimated stress drops are in the range of 376 to 572 bar. Ultimately, the strong ground motion parameters were investigated. Using a band-pass filter, all recordings were filtered and their acceleration, velocity and displacement time histories along with their response spectra were extracted, then the peak ground acceleration (PGA), velocity, and displacement of this earthquake were estimated. The PGA recorded at SPZ station on horizontal and vertical components (uncorrected data) are about 684, 554 and 385 cm/s2, respectively. Interestingly, there are two clear packets of energy in the recorded time histories of the Sarpol-e-Zahab, Kerend and some other stations that possibly indicate two sequential failures or two simultaneous seismic events. Considering the magnitude of the event, comparison of the observed values of maximum ground acceleration and velocity with the predicted values by ground motion predication equations presented by Boore et al. (2014), suggests that these equations are appropriate for the region.

کلیدواژه‌ها [English]

  • moment magnitude
  • Strong ground motion
  • Earthquake Source Parameters
  • Accelerograms
  • Brune source model

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