Focal Parameters Research Articles

Catalog of focal mechanism solutions for the Sichuan and Yunnan region from 2012 to 2022 using the community velocity model of Southwest China

The focal mechanism solution is one of the important focal parameters for exploring fault activity and studying regional stress distribution and it has a wide range of applications. The geological structure of the Sichuan-Yunnan region in China is complex, with frequent earthquakes and abundant historical observation data, making it one of the popular areas of concern for scholars. This study utilizes the high-precision community velocity model v2.0 of southwest China, obtained through joint inversion based on multiple data methods. The Cut-And-Paste (CAP) method was employed to fit and invert the observed waveforms of 1475 events with ML ​≥ ​3.5 in the Sichuan-Yunnan region from January 2012 to December 2022, thereby constructing a catalog of double-couple focal mechanisms. By comparing the focal mechanism inversion results of small earthquakes with those from multiple one-dimensional velocity models and conducting comparative statistical analysis on events below magnitude 4, it has been demonstrated that the model used in this study provides a better fit than one-dimensional models. This contributes to establishing the lower magnitude limit for producing deeper focal mechanism solutions. This study compares the results of larger magnitude earthquakes in the catalog with those published by the Global Centroid-Moment Tensor (GCMT) project and smaller magnitude earthquakes with the catalog released by the Institute of Earthquake Forecasting, China Earthquake Administration. These comparisons serve to validate the accuracy of the catalog results. Leveraging the high-resolution velocity model, this catalog has re-examined the historical earthquake focal mechanism catalog of the Sichuan-Yunnan region. The inversion has yielded reliable results for smaller magnitudes and a greater number of events, providing additional data and support for understanding the regional stress field, active faults, the mechanisms of large earthquake genesis, and earthquake prediction efforts. Consequently, this enhances the depth of scientific research in the Sichuan-Yunnan region.

Three-dimensional fault model and features of chained hazards of the Luding MS 6.8 earthquake, Sichuan Province, China

The MS 6.8 Luding earthquake in 2022 is located on the NNW-trending Moxi segment of the Xianshuihe fault with left-lateral strike-slip behavior. This area is where the Xianshuihe, Anninghe, Daliangshan and Longmenshan faults intersect. China Earthquake Administration has identified that intersection area, among the Moxi segment of the Xianshuihe fault, the Anninghe fault, the Daliangshan fault and the southern part of the Longmenshan fault, as a high-magnitude earthquake hazard area. According to existing data on the Luding earthquake, including the focal parameters, the spatial distribution of re-located aftershocks, dominated azimuth of the earthquake intensities and earthquake-induced ground fissures, we built a 3D earthquake fault model. We found that two discontinuous NNW-trending vertical strike-slip faults with left stepping were the seismogenic faults of the Luding earthquake. Its coseismic left-lateral dislocation triggered transtensional slips and aftershocks on the NW-trending secondary faults at its northernmost tensile area. Meanwhile, local crustal coseismic shortening on the side of Mt. Gongga triggered the aftershocks on the NE- and NW-trending secondary conjugated strike-slip faults, which were confirmed by GNSS observations and InSAR deformation field around the epicenter. This earthquake rupturing pattern also controlled the spatial distribution of the earthquake intensity IX area and earthquake chain hazards. The Coulomb stress calculation shows that the Luding earthquake increases the risk of high-magnitude earthquake occurrence on the southernmost part of the Xianshuihe fault and the Anninghe fault. Finally, we suggested doing good monitoring of the Anninghe fault and the southernmost part of the Xianshuihe fault and avoiding active faults with seismogenic capacity and areas prone to earthquake-chained hazards during the site selection and planning of reconstruction.

Rapid determination of source parameters of the M6.2 Jishishan earthquake in Gansu Province and its application in emergency response

In this study, we swiftly determined the focal parameters (focal mechanism, seismic imaging process, magnitude) of the Jishishan earthquake, leveraging a solved fault model to assess the intensity field and casualties promptly. The investigation began by retrieving the source mechanism through the P-wave initial motion and W-phase method. This enabled us to chart the spatial and temporal distribution of energy release in the source area via the back-projection technique. Following this, we estimated the earthquake's intensity field by merging the source inversion findings with the ground motion prediction equation. This analysis facilitated the evaluation of earthquake casualties, utilizing the theoretical intensity field and a casualty assessment model. Our findings indicate that the fault type is a thrust fault, characterized by a unilateral rupture in the direction of NW, with a rupture length spanning approximately 10–15 ​km and a duration ranging between 8 and 10 ​s. The earthquake's magnitude varied from M 5.9 to M 6.2. The demarcated high-intensity areas, as per our intensity assessment, align closely with the actual survey results. Furthermore, the predicted total casualties and identified critical rescue zones closely match the real-world casualty figures. These insights offer crucial technical support for governmental emergency command and rescue operations.

Rayleigh length extension in long-distance free-space optical communications based on lens group optimization

In the field of high-speed data transmission, wireless optical communications provide a paradigm shift from the conventional tethered connections, offering promising bandwidth and minimal latency. The cornerstone of such systems lies in their ability to precisely control the propagation of Gaussian beams, which are favored due to their inherent properties of minimal divergence and high spatial coherence over long distances. Efficient transmission hinges on the proper manipulation of these beams’ spatial characteristics, particularly the waist radius and the associated Rayleigh length, which together delineate the beam’s diffraction and spread. This manuscript methodically explores the theoretical and practical aspects of Gaussian beam focusing through lens systems, aiming to elucidate the pivotal relationship between the optimally adjusted focal parameters and the resultant augmentation of the Rayleigh length. Through rigorous diffraction integral simulations and a keen analysis of constraints posed by finite apertures, the study articulates strategies to considerably enhance the Gaussian beam’s propagation characteristics, thereby bolstering the reliability and efficacy of wireless optical communication systems.

Сейсмотектонические деформации и сброшенные напряжения землетрясений Центрального Тянь-Шаня

Based on the seismic moment tensor (SMT) data of 270 earthquakes in the Central Tien Shan, which occurred from 1978 to 2021 and include 63 events from the Global Centroid Moment Tensor catalog and 207 events from the works of Aleksander D. Kostyuk and Naylya A. Sycheva, the focal parameters (seismotectonic deformations (STD), kinematic and dynamic parameters, source radius, and stress drop) were calculated. The STD calculation was based on the approaches proposed in the studies of Yuriy V. Riznichenko and Sergei L. Yunga. The area under consideration is characterized by such deformation modes as thrust, transpression, underpression, and oblique. The distribution of the Lode–Nadai coefficient was calculated and plotted. A significant part of the study area is characterized by simple compression deformation, dominated by simple compression and simple shear. To calculate the stress drop , the values of the scalar seismic moment M0, which are determined in the SMT calculation, and the source radii r, which are calculated on the basis of theoretical and experimental models of the dependence of the source radius on the moment magnitude, were used. The radii r and stress drops  were calculated for two models of earthquake sources: the Brune model and the Madariaga–Kaneko–Shearer model. A catalog of dynamic parameters was compiled. The comparison of the kinematic and dynamic parameters of earthquakes was carried out, and the relationship of the dropped stresses with the type of movement in the source, as well as with the Lode–Nadai coefficient, was established. The results obtained in the study can be useful for specialists in other fields of knowledge – geodesy, geology, and geophysics.

SEISMICITY of the ARCTIC in 2018–2019

The article provides an overview and analysis of seismicity within the boundaries of the Arctic region for 2018–2019, a description of seismic station networks, and processing methods. The consolidated catalog of earthquakes in the Arctic region was compiled on the basis of catalogs of several organizations and seismological centers. In total, 1177 earthquakes for 2018–2019 are included in the consolidated catalog. Most of the earthquakes that occurred in 2018–2019, including all the strongest earthquakes, were located within the mid-ocean ridges of Mon, Knipovich. and Gakkel. In the offshore territories, most of the earthquakes were confined to the Svalbard archipelago, in particular, to the seismically active zone in the Sturfjord strait. Within the shelf areas, seismicity is also characteristic of the "continent-ocean" transition zone of the Barents-Kara region, Bely (Kvitøya) Island and Novaya Zemlya archipelago. For 28 earthquakes, the focal mechanism parameters are presented according to the Global CMT catalog.

New Insight on the Active Fault System in the Halmahera Volcanic Arc, Indonesia, Derived from the 2022 Tobelo Earthquakes

Abstract On 9 January 2022, two shallow earthquakes occurred in the east arm of Halmahera, Indonesia, with magnitudes of Mw 5.2 and 5.4 felt at III–V modified Mercalli intensity. The existence of the causative fault for the earthquakes was unknown. One possible explanation is that the earthquakes were caused by the activity of an inactive fault striking in the southeast–northwest direction, and possibly linked to the volcanic activities in Halmahera. Thus, further analysis of their characteristics is crucial to identify the previously an inactive fault. In this study, we relocated the associated earthquake hypocenters using the double-difference method with an updated velocity model, and determined the focal mechanisms by employing full waveform inversion using moment tensor analysis. The focal parameters were used to analyze the static stress changes. The relocated hypocenters show specific hypocenter clusters, aligning in the north–south direction, associated with left-lateral faulting mechanisms. This north–south alignment differs from the northeast–southwest trend of some other active faults in Halmahera. We propose that the newly found Tobelo fault dips at an angle of around 80° to the west. The seismic stress change from the mainshock and the foreshock of the Tobelo earthquakes corresponds with the distribution of the aftershocks. A detailed analysis of unidentified faults in the high seismicity area is essential to comprehend the tectonic study of Halmahera Island and its seismic hazard assessments.

Evaluating a Prospective Fault-Based Stress-Transfer Forecast for the M 7.9 Wenchuan Earthquake Region, 15 Years Later

Abstract Four days after the 12 May 2008 M 7.9 Wenchuan earthquake struck the Sichuan region of China, we submitted a prospective earthquake forecast based on transfer of stress from the mainshock onto significant faults crossing through populated areas. We identified where the largest aftershocks were likely to occur that could cause loss of life. We returned the revised article to the journal on 5 June 2008, marking the last day of our observation period. The primary testable features are locations and focal mechanisms of larger (M ≥ 4.5) earthquakes; did these events happen on or very near the faults we said they would? Did they have the same strikes, dips, and rakes as the faults we modeled? In retrospect, is the stress transfer method consistent with all M ≥ 4.5 earthquakes that occurred? We find all but one M ≥ 4.5 aftershock with known focal mechanisms located on stress-increased faults, and their focal mechanism parameters overlap with geological characteristics we used in making calculations. Six of the seven lethal M > 4.5 earthquakes that occurred in the region since 5 June 2008 were located on stress-increased faults, with the lone exception triggered by hydraulic fracturing.

Spatio-temporal structuring control of a vectorial focal field.

Focal field modulation has attracted a lot of interest due to its potential in many applications such as optical tweezers or laser processing, and it has recently been facilitated by spatial light modulators (SLMs) owing to their dynamic modulation abilities. However, capabilities for manipulating focal fields are limited by the space-bandwidth product of SLMs. This difficulty can be alleviated by taking advantage of the high-speed modulation ability of digital micromirror devices (DMDs), i.e.,trading time for space to achieve fine focus shaping. In this paper, we propose a new, to the best of our knowledge, technique for achieving four-dimensional focal field modulation, which allows for independent manipulation of the focal field's parameters (including amplitude, phase, and polarization) in both the space and time domains. This technique combines a DMD and a vector field synthesis system based on a 4-f system. The high-speed modulation ability of DMDs enables versatile focus patterns to be fast switchable during the exposure time of the detector, forming multiple patterns in a single recording frame. By generating different kinds of focal spots and lines at different moments during the exposure time of the detector, we can finally get complete multifocal spots and lines. Our proposed method is effective at improving the flexibility and speed of the focal field modulation, which is beneficial to applications.

Normative expression and accurate understanding of focal mechanism parameters

This paper aims at the understanding of the relationship between the upper and lower hemisphere projection maps of the focal sphere, the correct reading of the focal mechanism parameters on the projection diagram, and to investigate if there is uncertainty about whether the slip angle has a unique solution when there are only two nodal strikes and dip angles. Based on the principle of stereographic projection, the following four expressions and understanding skills about focal mechanism parameters are refined: (1) according to the principle of stereographic projection, we analyzed the difference of the presentation of focal mechanism parameters on different projection maps. There is a 180° rotation relationship between the upper and the lower hemisphere projection map. (2) The method of determining the nodal strike on the upper and lower hemisphere projections: for the former, the observer faces the convex direction of the nodal arc, and the direction to the right of the nodal plane is the stike of the fault. The angle turned clockwise in the north direction is the strike angle of the nodal plane; For the latter, the observer faces the convex direction of the arc of the nodal plane, and the point corresponding to the point on the right side of the nodal plane plus 180° is the strike of the fault. (3) The relationship between the azimuth angles of the P, T and N-axis on upper and lower hemisphere projections: the azimuth angles of the P, T, and N-axis on the upper hemisphere projection map = the azimuth angles of the P, T, and N-axis on the lower hemisphere projection map + 180°. (4) Only the strike and dip angles of two nodal planes are used to derive the rake: according to the slip angle formula, two groups of rake solution can be calculated, indicating that the solution are not unique. The actual slip angle can be determined by combining the hanging wall and footwall and strike of fault, or by combining the actual P-axis and T-axis data, or the first motion of P-waves. Aims to aid accurate understanding and long-term memory of focal mechanism parameters with consistent and simple rules.

Accelerating low-frequency ground motion simulation for finite fault sources using neural networks

SUMMARYIn the context of early emergency response to moderate and large earthquake shaking, we present a simulation based low-frequency ground motion estimation workflow that expedites an existing simulation method while taking into account simplified source process information. We focus on using source information that can be expected to be available shortly after an impacting earthquake, for example moment-tensor and simple finite-fault parameters. We utilize physics-based simulations which can include effects based on source orientation or finite faults, like rupture directivity. In order to keep the computational effort within feasible bounds and to apply the approach on global scale, we restrict ourselves to a low-frequency setup (standard 1-D layered earth model and 2 Hz sampling frequency) for either a moment tensor or a simple kinematic finite fault model. From the simulated records we then extract ground motion parameters of interest for arbitrary locations within the area of expected impact and display the expected spatial patterns of ground motion. Although simulations are kept simple, the results from this low-frequency ground motion parameter simulation (e.g. for peak-ground displacement) are in good agreement with observations from two well-studied earthquakes and partially more accurate than traditional, more empirical approaches (standard deviation <0.3 log10 units). However, waveform calculation and subsequent ground motion parameter extraction is computationally expensive. For a significant computational speedup in the context of rapid ground motion assessment, we directly train neural network (NN) models from large sets of source model information and their corresponding spatial ground motion distribution. We show that the trained NNs are able to reproduce the earthquake source related effects, like directivity and focal mechanism patterns, of the ground motion in any case. Given a set of source parameters, we obtain prediction errors smaller than 0.05 log10 units (ca. 11 per cent) and a magnitude dependent increase in computational speed of more than 1000 times compared to the initial waveform modelling. The proposed procedure enables thus to immediately compute probabilistic ground motion maps related to uncertainties in source parameters estimates, for example by sampling distributions based on parameter uncertainties or directly from an existing ensemble of focal parameter solutions.

The June 2022 Khost earthquake in southeastern Afghanistan: A complicated shallow slip event revealed with InSAR

On June 22, 2022, the Mw6.2 earthquake in southeastern Afghanistan caused a severe disaster. We used the Sentinel-1A ascending and descending track images of the European Space Agency and interferometric synthetic aperture radar (InSAR) to obtain the coseismic surface deformation field of the earthquake, which showed that the earthquake caused complex ruptures of multiple faults and various types. Using the dislocation model of the elastic half-space, we determined the focal parameters and slip distribution on the fault plane of this event. The results reveal that: (1) the seismogenic fault of this event is an unknown fault on the northeastern edge of the Katawaz microblock; (2) The slip on the fault plane is mainly in the range of 0–8 km along the dip, with maximum slips about 2 m at a depth of 2 km, which projected on the surface is 69.44°E, 32.96°N. This event suggests that, similar to the Chaman, Ghazaband and other large faults, the faults inside the microblock also play an important role in adjusting for the collision stress between India and Europe.

Skin γδ T cell inflammatory responses are hardwired in the thymus by oxysterol sensing via GPR183 and calibrated by dietary cholesterol

Dietary components and metabolites have a profound impact on immunity and inflammation. Here, we investigated how sensing of cholesterol metabolite oxysterols by γδ Tcells impacts their tissue residency and function. We show that dermal IL-17-producing γδ T (Tγδ17) cells essential for skin-barrier homeostasis require oxysterols sensing through G protein receptor 183 (GPR183) for their development and inflammatory responses. Single-cell transcriptomics and murine reporter strains revealed that GPR183 on developing γδthymocytes is needed for their maturation by sensing medullary thymic epithelial-cell-derived oxysterols. In the skin, basal keratinocytes expressing the oxysterol enzyme cholesterol 25-hydroxylase (CH25H) maintain dermal Tγδ17 cells. Diet-driven increases in oxysterols exacerbate Tγδ17-cell-mediated psoriatic inflammation, dependent on GPR183 on γδ Tcells. Hence, cholesterol-derived oxysterols control spatially distinct but biologically linked processes of thymic education and peripheral function of dermal Tcells, implicating diet as a focal parameter of dermal Tγδ17 cells.

Tectonic stress of northeastern Indian region derived from seismic focal mechanisms and the effect of focal mechanism on stress drop: a comparative analysis with Kachchh intraplate region of India

SUMMARY In this study, the focal mechanism solutions and source parameters of recent earthquakes that occurred in the northeastern region of India have been determined. The region has very complex tectonics as it is subjected to the compressional forces from all sides, due to the collision of the Indian Plate with the Eurasian, Burma and Tibetan plates. Waveform data from deployed broad-band seismographs (BBS) and strong motion accelerographs (SMA) in the northeastern India are used to determine the focal mechanism solutions and source parameters of moderate earthquakes, respectively. The estimated focal mechanisms are used to understand the existing stress field in the region. It is found that the Shillong-Plateau as well as the Indo-Burma subduction zone is dominated by the compressional tectonic regime, Mikir Hills and Bengal basin are dominated by the trans-tension tectonic regime, and the easternmost Himalayan region is dominated by the strike-slip tectonic regime. The maximum horizontal stress direction Shmax is also determined for above subregions. The direction of Shmax is southeast in the Bengal basin, northeast in Mikir Hills and Indo-Burma subduction zone whereas it is NNE in Shillong Plateau and SSW in the eastern Himalayas. The estimated stress drop value of the earthquakes in the region ranges from 2.11 to 23.89 MPa. The relationship between the source parameters and focal mechanisms is also explored. It is found that the earthquakes with a strike-slip mechanism have the highest average stress drop (7.05 MPa) followed by reverse (6.82 MPa) and normal (5.12 MPa) in the northeastern region of India. According to the examined data set, the stress drop is found to be dependent on the type of focal mechanism, seismic moment and hypocentral depths. The comparison of the results with the Kachchh intraplate region in western India shows earthquakes in Kachchh have larger mean stress drop for all types of mechanisms. In both intraplate and interplate regions of India, the stress drop of earthquakes depends on the type of focal mechanism solution.

Relativistic Problem of Two Bodies

This paper presents a developed theory of gravitational interaction of two-point bodies that takes into account the finiteness of the speed of light. The relativistic inertial (or gravitational) mass has been determined. The relativistic force of inertia, whose value is invariant to the Lorentz transformation, has been determined. A generalized form of the law of universal gravitation is presented, such that the gravitating masses in it contain corrective relativistic multipliers. Based on these new definitions, a method similar to that of classical mechanics is used to calculate a relativistic orbit of circulation. A new formula for the angle of displacement of perihelion, which takes into account both the value of the focal parameter and the eccentricity of the orbit, and which for the planet Mercury gives the correct numerical result, has been derived.

A general approximation to nested Bayes factors with informed priors

A staple of Bayesian model comparison and hypothesis testing Bayes factors are often used to quantify the relative predictive performance of two rival hypotheses. The computation of Bayes factors can be challenging, however, and this has contributed to the popularity of convenient approximations such as the Bayesian information criterion (BIC). Unfortunately, these approximations can fail in the case of informed prior distributions. Here, we address this problem by outlining an approximation to informed Bayes factors for a focal parameter . The approximation is computationally simple and requires only the maximum likelihood estimate and its standard error. The approximation uses an estimated likelihood of and assumes that the posterior distribution for is unaffected by the choice of prior distribution for the nuisance parameters. The resulting Bayes factor for the null hypothesis versus the alternative hypothesis is then easily obtained using the Savage–Dickey density ratio. Three real‐data examples highlight the speed and closeness of the approximation compared with bridge sampling and Laplace's method. The proposed approximation facilitates Bayesian reanalyses of standard frequentist results, encourages application of Bayesian tests with informed priors, and alleviates the computational challenges that often frustrate both Bayesian sensitivity analyses and Bayes factor design analyses. The approximation is shown to suffer under small sample sizes and when the posterior distribution of the focal parameter is substantially influenced by the prior distributions on the nuisance parameters. The proposed methodology may also be used to approximate the posterior distribution for under .

Studying Cellular Focal Adhesion Parameters with Imaging and MATLAB Analysis

Studying Cellular Focal Adhesion Parameters with Imaging and MATLAB Analysis

Restoration of the focal parameters for an extreme-power laser pulse with ponderomotively scattered proton spectra by using a neural network algorithm

A neural network-based approach is proposed both for reconstructing the focal spot intensity profile and for estimating the peak intensity of a high-power tightly focused laser pulse using the angular energy distributions of protons accelerated by the pulse from rarefied gases. For these purposes, we use a convolutional neural network architecture. Training and testing datasets are calculated using the test particle method, with the laser description in the form of Stratton–Chu integrals, which model laser pulses focused by an off-axis parabolic mirror down to the diffraction limit. To demonstrate the power and robustness of this method, we discuss the reconstruction of axially symmetric intensity profiles for laser pulses with intensities and focal diameters in the ranges of 1021–1023 W cm−2 and ∼(1–4)λ, respectively. This approach has prospects for implementation at higher intensities and with asymmetric laser beams, and it can provide a valuable diagnostic method for emerging extremely intense laser facilities.

FOCAL PARAMETERS of CRIMEAN-BLACK SEA REGION EARTHQUAKES in 2016–2017

Focal parameters of twenty-one 2016–2017 earthquakes of the Crimean-Black sea region with KП=6.5–13.1 have been recovered. Solutions of focal mechanisms have been obtained for the four strongest earthquakes. The dynamic source parameters – scalar seismic moment M0, the radius of circular dislocation r0, released stress , shear deformation , apparent stress ησ, radiation friction r, average slip along fault ū, energy of dislocation formation in the source ЕU, moment magnitude Mw – have been restored for twenty-one earthquakes by 149 amplitude spectra using Brune theoretical dislocation model. The type of slip in the source of May 13, 2016, felt an earthquake, which happened near the southern coast of Crimea, is a strike-slip. The June 28, July 22 and October 15, 2016 earthquakes occurred in the Black sea basin under the action of horizontal compressive stress, the type of slip in the source is a reverse fault. In the source of the June 16, 2017 earthquake, a thrust of active rupture wing occurred under the action of horizontal compression stress of the meridional direction. This type of movement is typical for earthquakes in the eastern part of the Crimean-Black Sea region. The mechanism parameters of these earthquakes were used to determine the direction of the source radiation to the recording station to account for relevant amendments in the calculation of the seismic moment M0. In general, average values of M0 and r0 for 2016–2017 earthquakes were within the confidence intervals of long-term dependencies M0(KП), r0(KП). The best correspondence of seismic moment values to the long-term dependencies was obtained for the earthquakes of the June 28, July 22, October 15, 2016 and June 16, 2017, with known focal mechanisms because the corrections for real radiation direction Rφ were introduced in the formula for M0 calculation. For reliable estimates of the spectral and dynamic source parameters of the 2016–2017 Crimean earthquakes, only very clear records of body waves at seismic stations with reliable characteristics of recording equipment were used. The averaging of the source dynamic parameters was done by 2–10 station definitions, which provided a small value of standard deviations. In this regard, quantitative estimates of focal parameters can be classified as reliable for further use for scientific and scientific-applied problems, in particular, for the development of geodynamic models.

FELT EARTHQUAKE of JULY 4, 2017 with ML=3.7, I0=5–6 to NORTHWEST of the 1988 SPITAK EARTHQUAKE SOURCE ZONE

The instrumental data and results of macroseismic survey of the July 4, 2017 earthquake with ML=3.7, I0=5–6, occurred in the source zone of the devastating Spitak earthquake of 1988 with I0=10, are given. The earthquake was accompanied by a sound like an explosion. According to the focal mechanism parameters, a reverse faulting occurred along the NP1 plane of northwest strike and northeast dipping, or a thrust along the near-meridional NP2 plane dipping west. The migration of aftershocks to the north and east in October-December 2017 testifies in favor of choosing the NP1 nodal plane as the main one. An isoseismal map of the earthquake is constructed, according to which the isoseists are oriented to the northeast. The discrepancy between their orientation and the strike of the nodal planes is explained by the predominant influence on the macroseismic field of northeast oriented Akhourian fault, in the zone of which most of the surveyed settlements are located.