Rupture process of the 7 May 2020 Mw 5.0 Tehran earthquake and its relation with the Damavand stratovolcano, and Mosha Fault

In May 2020 an earthquake with Mw 5.0 struck at ~40 km east of Tehran metropolis and ~15 km south of the Damavand stratovolcano. It was responsible for 2 casualties and 23 injured. The mainshock was preceded by a foreshock with Ml 2.9 and followed by a significant aftershock sequence, including ten events with Ml 3+. The occurrence of this event raised the question of its relation with volcanic activities and/or concern about the occurrence of larger future earthquakes in the capital of Iran. Tehran megacity is surrounded by several inner-city and adjacent active faults that correspond to high-risk seismic sources in the area. The Mosha fault with ~150 km long is one of the major active faults in central Alborz and east of Tehran. It has hosted several historical earthquakes (i.e. 1665 Mw 6.5 and 1830 Mw 7.1 earthquakes) in the vicinity of the 2020 Mw 5.0 Tehran earthquake&#8217;s hypocenter. In this study, we evaluate the seismic sequence of the Tehran earthquake and obtain the full moment tensor inversion of this event and its larger aftershocks, which is a key tool to discriminate between tectonic and volcanic earthquakes. Furthermore, we obtain a robust characterization of the finite fault model of this event applying probabilistic earthquake source inversion framework using near-field strong-motion records and broadband seismograms, with an estimation of the uncertainties of source parameters. Due to the relatively weak magnitude and deeper centroid depth (~12 km), no static surface displacement was observed in the coseismic interferograms, and modeling performed by seismic records. Focal mechanism solution from waveform inversion, with a significant double-couple component, is compatible with the orientation of the sinistral north-dipping Mosha fault at the centroid location. The finite fault model suggests that the mainshock rupture propagated towards the northwest. This directivity enhanced the peak acceleration in the direction of rupture propagation, observed in strong-motion records. The 2020 moderate magnitude earthquake with 2 casualties, highlights the necessity of high-resolution seismic monitoring in the capital of Iran, which is exposed to a risk of destructive earthquakes with more than 10 million population. Our results are important for the hazard and risk assessment, and the forthcoming earthquake early warning system development in Tehran metropolis.

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The first month of the 2016 central Italy seismic sequence: fast determination of time domain moment tensors and finite fault model analysis of the ML 5.4 aftershock

Annals of Geophysics ◽

10.4401/ag-7246 ◽

2016 ◽

Vol 59 ◽

Author(s):

Laura Scognamiglio ◽

Elisa Tinti ◽

Matteo Quintiliani

Keyword(s):

Time Domain ◽

Moment Tensor ◽

Central Italy ◽

Model Analysis ◽

Fault Model ◽

Normal Faults ◽

Seismic Sequence ◽

Moment Tensors ◽

Finite Fault ◽

Finite Fault Model

We present the revised Time Domain Moment Tensor (TDMT) catalogue for earthquakes with M_L larger than 3.6 of the first month of the ongoing Amatrice seismic sequence (August 24th - September 25th). Most of the retrieved focal mechanisms show NNW–SSE striking normal faults in agreement with the main NE-SW extensional deformation of Central Apennines. We also report a preliminary finite fault model analysis performed on the larger aftershock of this period of the sequence (M_w 5.4) and discuss the obtained results in the framework of aftershocks distribution.

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Simulation of the MW = 7.9 Gulf of Alaska earthquake on January 23, 2018, by the stochastic finite fault model

Acta Geophysica ◽

10.1007/s11600-021-00562-0 ◽

2021 ◽

Author(s):

Li Qicheng ◽

Yuan Shupeng ◽

Zheng Xinjuan

Keyword(s):

Gulf Of Alaska ◽

Fault Model ◽

Finite Fault ◽

Finite Fault Model ◽

Alaska Earthquake

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Present-day orogenic processes in the western Kalpin nappe explored by interseismic GNSS measurements and coseismic InSAR observations of the 2020 Mw 6.1 Kalpin event

Geophysical Journal International ◽

10.1093/gji/ggab097 ◽

2021 ◽

Author(s):

Ping He ◽

Yangmao Wen ◽

Shuiping Li ◽

Kaihua Ding ◽

Zhicai Li ◽

...

Keyword(s):

Source Parameters ◽

Satellite System ◽

Tien Shan ◽

Dislocation Model ◽

Maximum Displacement ◽

Finite Fault ◽

Instantaneous Deformation ◽

Gnss Measurements ◽

Global Navigation Satellite ◽

Finite Fault Model

Summary As the largest and most active intracontinental orogenic belt on Earth, the Tien Shan (TS) is a natural laboratory for understanding the Cenozoic orogenic processes driven by the India-Asia collision. On 19 January 2020, a Mw 6.1 event stuck the Kalpin region, where the southern frontal TS interacts with the Tarim basin. To probe the local ongoing orogenic processes and potential seismic hazard in the Kalpin region, both interseismic and instantaneous deformation derived from geodetic observations are employed in this study. With the constraint of interseismic global navigation satellite system (GNSS) velocities, we estimate the décollement plane parameters of the western Kalpin nappe based on a two-dimensional dislocation model, and the results suggest that the décollement plane is nearly subhorizontal with a dip of ∼3° at a depth of 24 km. Then, we collect both Sentinel-1 and ALOS-2 satellite images to capture the coseismic displacements caused by the 2020 Kalpin event, and the interferometric synthetic aperture radar (InSAR) images show a maximum displacement of 7 cm in the line of sight near the epicentral region. With these coseismic displacement measurements, we invert the source parameters of this event using a finite-fault model. We determine the optimal source mechanism in which the fault geometry is dominated by thrust faulting with an E–W strike of 275° and a northward dip of 11.2°, and the main rupture slip is concentrated within an area 28.0 km in length and${\rm{\,\,}}$10.3 km in width, with a maximum slip of 0.3 m at a depth of 6–8 km. The total released moment of our preferred distributed slip model yields a geodetic moment of 1.59 × 1018 N$\cdot $m, equivalent to Mw 6.1. The contrast of the décollement plane depth from interseismic GNSS and the rupture depth from coseismic InSAR suggests that a compression still exists in the Kalpin nappe forefront, which is prone to frequent moderate events and may be at risk of a much more dangerous earthquake.

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Comparative study of the 3D tsunami simulations performed with the use of different approaches to the reconstruction of the bottom movement

10.5194/egusphere-egu21-14950 ◽

2021 ◽

Author(s):

Kirill A. Sementsov ◽

Sergey V. Kolesov ◽

Anna V. Bolshakova ◽

Mikhail A. Nosov

Keyword(s):

Input Data ◽

Fault Model ◽

Earthquake Source ◽

Data Type ◽

Ocean Bottom ◽

Source Type ◽

Finite Fault ◽

Finite Fault Model ◽

Type 3

Information on the earthquake source mechanism (Centroid Moment Tensor) becomes publicly available in a few minutes after the earthquake (for example, https://earthquake.usgs.gov/earthquakes or http://geofon.gfz-potsdam.de/eqinfo). Using this information, we can calculate the ocean bottom displacement in the earthquake area [Leonard, 2010; Okada, 1985] and then use this displacement as an input data for hydrodynamic simulation of the tsunami waves. Let us call this type of input data - Type 1. Somewhat later (and sometimes much later), than CMT, more detailed information on the rupture fault structure (Finite Fault Model) becomes available. According to Finite Fault Model, the rupture fault in the earthquake source consists of a certain number of segments characterized by their dip and strike angles. Each segment consists of a finite number of rectangular subfaults, for each of which a displacement vector, an activation time and a rise time are specified. By applying Okada's formulas to each subfault and using the principle of superposition, we can calculate the ocean bottom displacement in the earthquake area and also use it as an input data for tsunami simulations. Let us call this type of input data - Type 2. However, based on the Finite Fault Model, we are able to create a third type of input data (Type 3). To do this, it is necessary to take into account the displacement start time (subfault activation time) and the displacement duration (subfault rise time) of each subfault and consider the dynamics of the rupture process. In this case, we will be able to reconstruct not only the coseismic bottom displacement in the earthquake source (Type 2), but also describe the dynamics of the coseismic bottom displacement formation in the tsunami source (Type 3).&#160;This paper compares the tsunami simulation results performed with the of different types of input data (Type 1, Type 2 and Type 3). We performed calculations for a number of large earthquakes at the beginning of the 21st century. We took all the earthquake source information from the USGS catalog (https://earthquake.usgs.gov/earthquakes). The bottom deformations of all three types were calculated using the ffaultdisp code (http://ocean.phys.msu.ru/projects/ffaultdisp/). Tsunami modeling was carried out using a combined 2D / 3D CPTM model [Nosov, Kolesov, 2019; Sementsov et al., 2019]. The simulation results are compared with each other as well as with the DART ocean bottom observatories records.&#160;The study was supported by Russian Foundation for Basic Research (projects 20-35-70038, 19-05-00351, 20-07-01098).&#160;

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Estimation of the Rupture History of the 2008 Mw8.0 Wenchuan Earthquake by Joint Inversion of Teleseismic and Strong-Motion Records

Advances in Civil Engineering ◽

10.1155/2020/8810218 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Deyu Yin ◽

Yun Dong ◽

Qifang Liu ◽

Yuexin She ◽

Jingke Wu ◽

...

Keyword(s):

Wenchuan Earthquake ◽

Strong Motion ◽

Inversion Method ◽

Near Surface ◽

Strong Motion Records ◽

The Wenchuan Earthquake ◽

Finite Fault ◽

History Of ◽

Beichuan Fault ◽

Dip Angle

In order to reproduce the rupture history of the 2008 Mw8.0 Wenchuan earthquake, the teleseismic and strong-motion records are adopted. Based on a multiple-segment, variable-slip model, the finite fault inversion method is utilized to recover the rupture process. The results are as follows: (1) the rupture duration of the Wenchuan earthquake is about 100 s, and the released seismic moment is 1.24 × 1021 N·m, equal to the moment magnitude Mw8.0. There are 5 asperities on the fault plane, indicating that the earthquake is composed of at least 5 subevents. (2) The slip is mainly distributed on the Beichuan fault, indicating that the Beichuan fault is the main rupture fault. On the southern part of the Beichuan fault, the dislocation underside the Longmenshan area and Hongkou-Yingxiu near-surface area is dominated by thrust, and the maximum slip is 11.8 m. Slip between the Yuejiashan and Qingping area is dominated by thrust. On the northern part of the Beichuan fault, the area under Beichuan is dominated by thrust, the slip under Nanba is thrust and strike, near Qingchuan, the slip turns into the strike slip, and the maximum slip is 13.1 m. The dislocation under Bailu is also dominated by thrust, with maximum slip 8.9 m. (3) The rupture of the Wenchuan earthquake is mainly a unilateral rupture to the northeast. The rupture started at the low dip angle part of the Beichuan fault, and after 3 s, it propagated to the Pengguan fault. After 10 s, the largest asperity under Longmenshan in the south section of the Beichuan fault began to break, lasting for about 24 s. Then, the Xiaoyudong fault was triggered by the Pengguan fault, and the bilateral rupture of the high dip angle part of the Beichuan fault started at about 6 s. South section of the Beichuan fault began to break at about 35 s, and at 43 s, 63 s, and 80 s, the rupture extended to Beichuan, Nanba, and Qingchuan areas.

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Speeding up and boosting tsunami warning in Chile

10.5194/nhess-2019-9 ◽

2019 ◽

Author(s):

Mauricio Fuentes ◽

Sebastian Arriola ◽

Sebastian Riquelme ◽

Bertrand Delouis

Keyword(s):

Real Time ◽

Near Field ◽

Linear Method ◽

Seismic Energy ◽

Fault Model ◽

Tsunami Forecast ◽

Finite Fault ◽

Run Up ◽

Finite Fault Model ◽

Chile Tsunami

Abstract. Chile host a great tsunamigenic potential along its coast, even with the large earthquakes occurred during the last decade, there is still a large amount of seismic energy to release. This permanent feature and the fact that the distance between the trench and the coast is just 100 km creates a difficult environment to do real time tsunami forecast. In Chile tsunami warnings are based on reports of the seismic events (hypocenter and magnitude) and a database of precomputed tsunami scenarios. However, because yet there is no answer to image the finite fault model within first minutes (before the first tsunami wave arrival), the precomputed scenarios consider uniform slip distributions. Here, we propose a scheme of processes to fill the gaps in-between blind zones due to waiting of demanding computational stages. The linear shallow water equations are solved to obtain a rapid estimation of the run-up distribution in the near field. Our results show that this linear method captures most of the complexity of the run-up heights in terms of shape and amplitude when compared with a fully non-linear tsunami code. Also, the run-up distribution is obtained in quasi real-time as soon as the seismic finite fault model is produced.

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Quick determination of earthquake source parameters from GPS measurements: a study of suitability for Taiwan

Geophysical Journal International ◽

10.1093/gji/ggz359 ◽

2019 ◽

Vol 219 (2) ◽

pp. 1148-1162

Author(s):

Jiun-Ting Lin ◽

Wu-Lung Chang ◽

Diego Melgar ◽

Amanda Thomas ◽

Chi-Yu Chiu

Keyword(s):

Rapid Determination ◽

Moment Tensor ◽

Near Field ◽

Source Parameters ◽

Early Warning Systems ◽

Earthquake Magnitude ◽

Observation System ◽

Earthquake Source Parameters ◽

Finite Fault

SUMMARY We test the feasibility of GPS-based rapid centroid moment tensor (GPS CMT) methods for Taiwan, one of the most earthquake prone areas in the world. In recent years, Taiwan has become a leading developer of seismometer-based earthquake early warning systems, which have successfully been applied to several large events. The rapid determination of earthquake magnitude and focal mechanism, important for a number of rapid response applications, including tsunami warning, is still challenging because of the limitations of near-field inertial recordings. This instrumental issue can be solved by an entirely different observation system: a GPS network. Taiwan is well posed to take advantage of GPS because in the last decade it has developed a very dense network. Thus, in this research, we explore the suitability of the GPS CMT inversion for Taiwan. We retrospectively investigate six moderate to large (Mw6.0 ∼ 7.0) earthquakes and propose a resolution test for our model, we find that the minimum resolvable earthquake magnitude of this system is ∼Mw5.5 (at 5 km depth). Our tests also suggest that the finite fault complexity, often challenging for the near-field methodology, can be ignored under such good station coverage and thus, can provide a fast and robust solution for large earthquake directly from the near field. Our findings help to understand and quantify how the proposed methodology could be implemented in real time and what its contributions could be to the overall earthquake monitoring system.

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Stochastic Source Model for Strong Motion Prediction

International Journal of Geotechnical Earthquake Engineering ◽

10.4018/ijgee.2018070101 ◽

2018 ◽

Vol 9 (2) ◽

pp. 1-22

Author(s):

S. Sangeetha ◽

S.T.G. Raghukanth

Keyword(s):

Near Field ◽

Source Parameters ◽

Strong Motion ◽

Seismic Source ◽

Source Model ◽

Spectral Density Function ◽

Correlation Lengths ◽

Rupture Area ◽

Power Spectral ◽

Finite Fault

The article aims at developing a stochastic model which simulates spatial distribution of slip on the fault plane. This is achieved by analysing a large dataset of 303 finite-fault rupture models from 152 past earthquakes with varying fault mechanisms and in the magnitude range of 4.11-9.12. New scaling relations to predict the seismic source parameters such as fault length, fault width, rupture area, mean and standard deviation of slip have been derived for distinct fault mechanisms. The developed methodology models the spatial variability of slip as a two-dimensional von Karman power spectral density function (PSD) and correlation lengths are estimated. The proposed stochastic slip model is validated by comparing the simulated near-field ground response with the recorded data available for the 20th September 1999 Chi-Chi earthquake, Taiwan.

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