بررسي كيفيت داده‌هاي ثبت‌شده با شتاب‌سنج گوشي‌هاي هوشمند براي مطالعات مهندسي زلزله

Reliability of Seismic Data Recorded by Smartphone Accelerometers for Earthquake Engineering Applications

امروزه گوشي هاي هوشمند با انواع حسگرها ازجمله شتاب‌سنج، مغناطيس سنج و سامانه موقعيت يابي جغرافيايي (GPS) مجهز شدهاند؛ ازاين‌رو، گوشيهاي هوشمندي كه قبل از رويداد زلزله در موقعيت ساكن قرار دارند، ميتوانند به‌عنوان يك شبكه بزرگ از لرزه نگارهايي با كيفيت ضعيف تا متوسط براي ارزيابي خطر زلزله، تهيه نقشه لرزش و مديريت بحران رخداد زلزله استفاده شوند. در اين مقاله، هدف آن است تا با ساخت يك نرم‌افزار كاربردي (اپليكيشن) اندرويد، داده­ هاي شتاب­ سنج گوشي هوشمند ثبت و توانايي گوشي­ هاي هوشمند در ثبت مناسب داده زلزله، بازسازي محتواي بسامدي در گستره بسامدي مورد نياز در مهندسي زلزله، بيشينه دامنه ­هاي شتاب، سرعت و جابه­ جايي (كه در برآورد آسيب ساختمان به كار مي­آيند) و طيف­ هاي فوريه و پاسخ ارزيابي شود. همچنين ميزان تأثيرپذيري اين شاخصه‌ها از لغزش گوشي نامتصل به زمين نيز بررسي شده است. براي شبيه­ سازي تحريك­ هاي هارمونيك و حركت زلزله از ميز لرزان استفاده شده و داده ­هاي برداشت­ شده براي دو گوشي هوشمند آزمون با داده ­هاي ثبت­ شده با شتاب‌نگار مرجع مقايسه شده است. مقايسه شاخصه‌هاي لرزه­اي نشان مي­دهد استفاده از شتاب­ سنج­ هاي گوشي­ هاي همراه در توسعه يك شبكه گسترده شتاب‌نگاري شهري براي مطالعات مهندسي زلزله توجيه­ پذير است.

Today, smartphones are well equipped with various sensors such as accelerometers, magnetometers and GPS devices. The smartphones that are installed on the ground and may not experience a considerable slipping, may effectively be used as a large network of low to moderate seismometers. This smartphone-based seismic network can efficiently serve for producing shake maps, earthquake risk and hazard assessment and analysis, and earthquake crisis management. In this article, an Android application is developed by Java-programming in Android Studio IDLE to record and save three components of acceleration data that are sensed by smartphone accelerometers, and send them to a local server. The feasibility of smartphone accelerometers are then investigated for developing any future smartphone-based seismic networks especially for earthquake engineering applications. For this purpose, several important criteria such as recorded acceleration data (for the three components), peak ground accelerations (PGA), peak ground velocities (PGV), peak ground displacements (PGD), as well as Fourier and response spectra and Arias intensities are derived for two test smartphones and a reference professional Güralp accelerometer. The effect of smartphone slipping with respect to the ground during the earthquake data recording is also investigated. Harmonic oscillations with different frequencies and Bam earthquake movements are simulated by a shaking table that is designed and manufactured in the Earthquake Research Center (EQRC), Ferdowsi university of Mashhad. The above mentioned criteria derived from the recorded seismic data for the two test mobile sets are compared with those of reference Güralp accelerometer. The results show that the frequency range provided by the seismic data recorded by smartphone accelerometers is efficiently enough for any earthquake engineering application (0.1 to 10~20 Hz), especially for short to medium buildings. The accuracy of such devices are well enough to record seismic movements produced by nearly severe earthquakes with magnitudes > 5 at epicentral distances < 200 km. It is also shown in this article that small relative movements of mobile sets on their base may have little effect on seismic criteria and may not harmfully deviate the results. Sensitivity of the test mobiles to trigger earthquakes with magnitudes > 4.5 at epicentral distance of 10 km is also investigated. As a whole, application of smartphone accelerometers seems to be strongly justified for developing any seismic data aimed at earthquake engineering applications and earthquake crisis management. The EQRC team is now developing its smartphone–based seismic network on small to moderate scales and is testing different protocols for an efficient data transfer.