تعیین پارامترهای چشمه نقطه‌ای و گسترده زمین‌لرزه 5 آوریل 2017 سفیدسنگ (0/6Ml ) در حوزه زمان و فرکانس با استفاده از مجموعه‌ابزار KIWI

نوع مقاله : پژوهشی

نویسندگان

1 دانش‌آموخته کارشناسی ارشد، گروه زلزله شناسی، مؤسسه ژئوفیزیک، دانشگاه تهران، تهران، ایران

2 دانشیار، گروه زلزله شناسی، مؤسسه ژئوفیزیک، دانشگاه تهران، تهران، ایران

چکیده

مجموعه ابزار KIWI (KInematic Waveform Inversion)، یک روش جدید در تعیین سازوکار کانونی و پارامترهای چشمه زمین‌لرزه‌های ناحیه‌ای است که در آن با انجام برگردان در دو حوزه زمان و فرکانس، پارامترهای چشمه نقطه‌ای و گسترده تعریف شده در مدل چشمه اِیکونال (eikonal) طی فرآیندی مرحله‌ای تعیین می‌شود. هدف از این مطالعه، تعیین پارامترهای چشمه نقطه‌ای و گسترده زمین‌لرزه 5 آوریل 2017 سفیدسنگ (0/6Ml ) ضمن تشریح مراحل برگردان در مجموعه ابزار KIWI است. شکل موج‌های استفاده شده در این تحقیق برگرفته از ایستگاه‌های دائمی باندپهن پژوهشگاه بین‌المللی زلزله‌شناسی و مهندسی زلزله (IIEES) و شبکه جهانی IRIS است. به­منظور ارزیابی عملکرد مجموعه ابزار KIWI، فرآیند برگردان با استفاده از شش زیرگروه اطلاعاتی مختلف (شامل مدل پوسته IASP91، مدل پوسته میانگین ایران (IRSC) و داده­های مذکور) انجام شده که در این بین مجموعه متشکل از مدل سرعتی IRSC و کل داده­های موجود به­عنوان مجموعه اطلاعاتی بهینه در نظر گرفته شده است. نتایج حاصل از برگردان با استفاده از مجموعه اطلاعاتی بهینه بیانگر جنبش عمدتاً معکوس با مؤلفه راستالغز راست­گرد با شیب به‌سمت شمال­شرق است که با مشخصات گسل کشف­رود همخوانی دارد. پارامترهای چشمه نقطه­ای نظیر عمق مرکزوار و بزرگای گشتاوری زمین­لرزه به‌ترتیب 1/7 کیلومتر و 2/6 به­دست آمد. برگردان پارامترهای چشمه گسترده نیز نتایجی چون جهت­یافتگی عمدتاً یک طرفه به­سمت جنوب شرق، مدت‌زمان شکست 3/9 ثانیه، مساحت شکست 300 کیلومتر مربع و نیز میانگین لغزش 16 سانتی­متر را به­دست داده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Determination of point and extended source parameters of 5 April 2017 Sefid-Sang earthquake (Ml 6.0) in time and frequency domains using KIWI tools

نویسندگان [English]

  • Alireza Niksejel 1
  • Zaher Hossein Shomali 2
1 M.Sc. Graduated, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran
2 Associate Professor, Department of Seismology, Institute of Geophysics, University of Tehran, Tehran, Iran
چکیده [English]

KIWI (KInematic Waveform Inversion) is a recently developed multi-step inversion tools at the Institute of Geophysics of University of Hamburg. The main aim of developing this method is to perform moment tensor inversion retrieving the point and extended source parameters in regional distances. In KIWI tools, point and kinematic source parameters are retrieved in a sequential process in three inversion steps in time and frequency domains using different inversion methods, parts of waveforms and so on. After the point source inversion done, the method retrieves the radiation pattern, including fault plain parameters, Scalar moment and centroid depth. Also, for large enough earthquakes (Mw>5.5), extended source inversion retrieves finite source parameters such as rupture directivity, rupture area and velocity, rise and rupture time, average slip and nucleation point regarding to the point source centroid location. KIWI tools uses pre-calculated Greens functions, hence, the inversion process is quite fast. Due to the same reason, this method is rendered for automatic real-time retrieval of point and extended source parameters. In general, we can highlight the most important characteristics and applications of KIWI tools as follows: ability of easy implementation for real-time retrieval of source parameters, stability of inversion, rapid directivity detection, no requirements of aftershocks and foreshocks, no limitation in depth and magnitude and ability of retrieving reliable results even in absence of accurate velocity model used to build the Green’s functions and large stations azimuthal gap. In this research, we introduce the KIWI tools and use its applications to study of the April 5, 2017 (Ml 6.0) Sefidsang-Fariman earthquake. The data used in this research were recorded by permanent broadband stations of International Institute of Earthquake Engineering and Seismology (IIEES) and some global broadband stations from IRIS network at a minimum epicenteral distance of 200 kilometers. To have a better evaluation of KIWI tools functionality, we made inversion of source parameters using six different set of information (including IASP91 and IRSC velocity models and the mentioned set of data). Then, the information set including IRSC velocity model and all available data considered as the optimum one. Comparing the obtained results using the optimum set of information and the remaining sets, Maximum difference in centroid depth, Latitude and Longitude is 1.9 kilometer, 0.23 and 0.5 degree related to information sets including only IRIS network data, while there is a good consistency in retrieved focal mechanisms. After all, it is tried to run a sensitivity test using the optimum information set to have a better assessment on KIWI tools stability in source parameters analysis. Based on the achieved results, the erroneous input parameters (e.g. Latitude, Longitude and Depth) had a low influence on our optimum results. The final results in this research represents the centroid of earthquake in a shallow depth (7.1 km) with a magnitude slightly larger than those published by other institutions like USGS (Mw 6.2). Retrieved focal mechanism shows mainly reverse faulting with small dextral strike-slip component dipping north-east which is in a good accordance with the Kashafrood fault characteristics as the closest active fault to the epicenter. Also, extended source inversion revealed mostly unilateral source directivity toward SE with a rupture area, rupture time and approximate average sleep of 300 km2, 9.3 seconds and 16 cm.

کلیدواژه‌ها [English]

  • KIWI tools
  • multistep inversion in time and frequency domains
  • point and extended source parameters
  • Sefidsang earthquake (Ml 6.0)
آقانباتی، ع.، 1383، زمین شناسی ایران، انتشارات سازمان زمین شناسی و اکتشافات معدنی کشور، تهران، ۶۷۷ ص.
بازرگان، س.، 1395، برگردان داده‌های لرزه‌ای برای تعیین توزیع لغزش زمین‌لرزه‌های 18 ژوئن 2007 با بزرگی 5/5 Mw و 27 سپتامبر 2010 با بزرگی 9.5 Mw با استفاده از روش برگردان لغزش: پایان نامه کارشناسی ارشد ژئوفیزیک، مؤسسه ژئوفیزیک دانشگاه تهران.
میرزایی، ن.، 1383، سمینار آموزشی مبانی لرزه‌زمین‌ساخت و تحلیل خطر نسبی زمین‌لرزه، مؤسسه ژئوفیزیک، دانشگاه تهران، ۷۳ ص. 
Aflaki, M., Ghods, A., Mousavi, Z., Shabanian, E., Vajedian, S. and Akbarzadeh, M., 2018, Seismotectonic characteristics of the 2017 Sefid Sang (Mw 6) earthquake, 18th Iranian Geophysical Conference, 68-71.
Aki, K., 1979, Characterization of barriers on earthquake fault, J. geophys. Res., 84, 6140-6148.
Aki, K. and Richards, P. G., 1980, Quantitative Seismology, W. H. Freeman, San Francisco, ISBN 0716710587.
Ashtari Jafari, M., 2019, Teleseismic moment tensors of the 5 April 2017, Mw6. 1, Fariman, northeast Iran, earthquake. Acta Geophysica, 67(2), pp.437-448.
Aster, R. C., Borchers, B. and Thurber, C., 2005, Parameter estimation and inverse problems, Academic Press.
Berberian, M., 1981, Active faulting and tectonics of Iran, Department of Earth Sciences, Bullard Laboratories, University of Cambridge, Madingley Rise, Madingley Rd., Cambridge CB3 OEZ, U.K.
Cesca, S., Buforn, E. and Dahm, T., 2006, Moment tensor inversion of shallow earthquakes in Spain, Geophysics, J. Int., 166, 839–854, doi:10.1111/j.1365-246X.2006.03073.x.
Cesca, S. and Heimann, S., 2013, A practical on moment tensor inversion using the Kiwi tools, doi: 10.2312/GFZ.NMSOP-2_EX_3.6.
Cesca, S. and Heimann, S., 2014, Rapidinv.py, release 14.0. A short user guide. GFZ Potsdam, S2.1.
Cesca, S., Heimann, S. and Dahm, T., 2011, Rapid directivity detection by azimuthal amplitude spectra inversion, Seismol, J. 15(1), 147-164, doi: 10.1007/s10950-010-9217-4.
Cesca, S., Heimann, S., Stammler, K. and Dahm, T., 2010, automated procedure for point and kinematic source inversion at regional distances, Geophysics. Res., 115(B14), B06304, doi: 10.1029/2009JB006450.
Dahm, T., Manthei, G. and Eisenblätter, J., 1999, Automated moment tensor inversion to estimate source mechanisms of hydraulically induced micro-seismicity in salt rock, Tectonophysics, 306, 1–7, doi: 10.1016/S0040-1951(99)00041-4.
Das, S. and Aki, K., 1977, Fault plain with barriers: a versatile earthquake model, J.geophys. Res., 82, 5658-5670.
Domingues, A., 2010, Kinematic Waveform Inversion-Study of Regional Earthquakes in Southwest Iberia, M.Sc thesis, university of Lisbon, senior technical institute.
Domingues, A., Custodio, S. and Cesca, S., 2012, Waveform inversion of small-to-moderate earthquakes located offshore southwest Iberia, Geophysics, J. Int. doi: 10.1093/gji/ggs010.
Hartzell, S. and Heaton, T. H., 1983, Inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 Imperial Valley, California, earthquake. Bull. Seism. SOC. Am., 73, 1553-1583.
Hartzell, S., Liu, P., Mendoza, C., Ji, C. and Larson, K. M., 2007, Stability and Uncertainty of Finite Fault Slip Inversions: Application to the 2004 Parkfield California Earthquake, Bulletin of the Seismological Society of America, 97, 1911-1934.
Heimann, S., 2011, A robust method to estimate kinematic earthquake source parameters, PhD thesis, University of Hamburg, Hamburg, Germany, 161 p.
Heimann, S., Cesca, S., Krüger, F. and Dahm, T., 2008, Stable estimation of extended fault properties for medium-sized earthquakes using teleseismic waveform data, Geophysical Research Abstracts, pp. EGU2008–A–07,568.
Jackson, J., 1992, Partitioning of strike-slip and convergent motion between Eurasia and Arabia in eastern turkey and the Caucasus, J. Geophys. Res Solid Earth, pp. 12471-12479.
Jackson, J. and McKenzie, D., 1984, Active tectonics of the alpine-himalayan belt between western Turkey and Pakistan, Geophys. J. Int., 77, 185-264.
Jackson, J. and McKenzie, D., 1988, the relationship between plate motions and seismic moment tensors, and the rates of active deformation in the Mediterranean and Middle East, Geophys. J. Int., pp. 45-73.
Lomax, A., Virieux, J., Volant, P. and Berge, C., 2000, Probabilistic earthquake location in 3D and layered models, Introduction of a Metropolis-Gibbs method and comparison with linear locations, in Advances in Seismic Event Location, Thurber, C.H., and N. Rabinowitz (eds.), Kluwer, Amsterdam, 101-134.
McGarr, A., 1981, Analysis of pick ground motion in terms of a model of inhomogeneous faulting, J. geophys. Res., 86, 3901-3912.
Menke, W., 1989, Geophysical data analysis, discrete inverse theory, Academic press.
Romanowicz, B. A., 1982, Moment tensor inversion of long period Rayleigh waves, A new approach: Geophysics, J. Res., 87, 5395–5407.
Yamashita, T. and Knopoff, L., 1987, Models of aftershock occurrence, geophys. J. R. astr. Soc, 91, 13-26.
Su, Z., Yang, Y., Li, Y., Xu, X., Zhang, J., Zhou, X., Ren, J., Wang, E., Hu, J.C., Zhang, S. and Talebian, M., 2019, Coseismic displacement of the 5 April 2017 Mashhad earthquake (Mw 6.1) in NE Iran through Sentinel-1A TOPS data: New implications for the strain partitioning in the  southern Binalud Mountains. Journal of Asian  Earth Sciences, 169,244-256.