Earthquake Mechanisms Research Articles

The rupture mechanisms of intraslab earthquakes: A multiscale review and re-evaluation

The initiation of intraslab earthquakes and their location depend on multiple factors such as slab heterogeneity, pre-subduction anisotropy, thermal parameters and the metamorphic history of the lithosphere slab. As a result, these failures occur over a range of temperature-pressure conditions through different mechanisms. Therefore, to unravel the intricacy of intraslab seismicity, it is crucial to investigate the details of failure mechanisms using multiple datasets, at different scales. Details on rupture mechanisms are now accessible through advanced, high-resolution seismologic approaches. However, seismologic archives are limited to events of the past few decades. Further, quasi-synchronous multiple-source mechanisms can be challenging to distinguish from seismic data only. Alternatively, the geologic records of intraslab seismicity, preserved in pseudotachylytes, provide a higher spatiotemporal resolution than seismic data, resulting in direct insight into the rupture triggering mechanisms.. These fault rocks also inform, over the geologic timescale, on the integrated deformation history of the slab. Despite this fact, only a handful of natural exposures have been investigated, and these include localities in Corsica, Italy, Zambia, and Japan. In addition, despite some strain rate limitations, deformation experiments, conducted using a wide range of starting materials and over broad pressure-temperature conditions, may further constrain the causes of intraslab rupture. These experiments, being intrinsically performed on relatively small rock volumes cannot capture large scale aspects of intraslab deformation. Finally, numerical modelling may overcome some of the above limitations as long as accurate and realistic parameters are chosen. Ultimately, our review shows that to fill the gap in our knowledge of intraslab seismicity, we need a multiscale-multimethod approach that integrates seismologic, geologic, experimental and numerical perspectives.

Sanding Wells on The Island of Lombok due to Earthquake Vibrations

The Lombok earthquake in 2018 was unique, the shocks occurred sequentially. Several major earthquakes were followed by thousands of aftershocks. The earthquake caused a devastating disaster which destroyed many homes, buildings including wells as the main fresh water supply in the Lombok Island. The focal mechanism of main earthquake shows a thrust fault mechanism. Lombok Island is originally a volcano Island which is still growing actively. Therefore surface of Island is dominated by volcanic materials, such as: volcanic rock, volcanic ash, pumice. This paper describes the phenomenon of sanding wells in Lombok, including the physical mechanisms among rock’s grains when vibrating earthquake waves. These earthquake waves can eliminate static friction between grains and reduce cohesion between grains of rock. Some subsurface images shows a strong correlation between damage grade and the existence of loose sand and hard rock.

Improving the Constraint on theMw7.1 2016 Off‐Fukushima Shallow Normal‐Faulting Earthquake With the High Azimuthal Coverage Tsunami Data From the S‐Net Wide and Dense Network: Implication for the Stress Regime in the Tohoku Overriding Plate

AbstractTsunamis with amplitudes of up to 40 cm, related to theMw7.1 normal‐faulting earthquake off Fukushima, Japan, on November 21, 2016, were clearly recorded by a new offshore wide and dense ocean‐bottom pressure gauge network, S‐net, with high azimuthal coverage located closer to the focal area. We processed the S‐net data and found some stations included the tsunami‐irrelevant drift and step signals. We analyzed the S‐net data to infer the tsunami source distribution. A subsidence region with a narrow spatial extent (∼40 km) and a large peak (∼200 cm) was obtained. The other near‐coastal waveforms not used for the inversion analysis were also reproduced very well. Our fault model suggests the maximum stress drop across the fault plane of >∼10 MPa and the average of 4.2 MPa, whereas the shear stress increase along the fault caused by the 2011 Tohoku earthquake was only ∼2 MPa. Past studies have suggested that horizontal compressional stress around this region switched to horizontal extensional stress after the Tohoku earthquake due to its stress perturbation. The present result, however, suggests that the horizontal extensional stress was locally predominant at the shallowest surface around the focal area even before 2011. The present study demonstrates that the S‐net high‐azimuthal‐coverage pressure data provide a significant constraint on the fault modeling, which enables us to discuss the stress regime within the overriding plate at the offshore. Our analysis provides an implication for crustal stress states, which is important for understanding generation mechanisms of intraplate earthquakes.

Focal Mechanism Analysis of the September 25th, 2019 Mw 6.5 Ambon Earthquake and Its Implication for Seismotectonics

On September 25th, 2019, an Mw 6.5 earthquake occurred in Ambon, Maluku Province, Indonesia, and caused casualties and infrastructures damages. The epicenter located in a tectonically active region with the potential strike-slip and thrust faulting earthquake sources, yet the responsible fault is still not well understood. Based on focal mechanism solutions from available seismological agencies, i.e. USGS, GFZ, GCMT, and BMKG, the earthquake has a similar strike-slip focal mechanism, although there are discrepancies on detailed source parameters. To provide a better understanding of the earthquake mechanism and seismotectonic, we apply the Cut-and-Paste (CAP) focal mechanism inversion method to broadband seismic waveforms from regional and teleseismic distances. The CAP inversion results on the regional data grouped in different distance ranges show a robust strike-slip solution. We then refine the earthquake focal depth by performing the CAPtele inversion and resulted in a depth of 12 km with similar fault plane solution as the regionals. The ruptured fault plane is resolved by a directivity analysis using azimuthal pattern of the apparent source durations, which indicates an obvious unilateral rupture propagation toward SSE direction. Our result suggests the NNW-SSE orientated fault is the ruptured fault plane, which is also consistent with the near N-S distributed aftershocks. This fault is located in a narrow sea between Seram, Ambon and Haruku island and was not reported yet in previous studies. The Coulomb failure stress (CFS) changes analysis of the mainshock shows that the Ambon earthquake has promoted the off-fault aftershocks which occurred to the west of the ruptured fault.

Earthquakes generated by fluid overpressure: Insights from cryptoexplosive breccias

The genetic mechanism of earthquakes remains puzzling even though some hypotheses for earthquake generation have been proposed. A new genetic model of earthquake was established by studying the dynamical relationship between earthquake generation and cryptoexplosion. More and more cryptoexplosive breccias that were naturally produced by explosion or detonation below the surface have been found throughout the world. The endogenic cryptoexplosive breccias (CEBs) have been found at hundreds of sites in China, most of which were dated in the Yanshanian period, some in Preyanshanian, and dozen in the Himalayan period. The breccias are characterized by the angular fragments produced by hydrothermal and magmatic explosions, the network and jigsaw textures, and the matrices that originated from magma or geothermal fluids. The high energy fluids derived from the lower mantle accumulated at some places during upward migration, at which the fluid explosions occurred when the fluid pressure exceeded the confined pressure of the host rocks. As a result, innumerable paleoearthquakes were produced by the prevailing cryptoexplosions in the geological history. Such geological processes never end, as geothermal and volcanic activities do. Therefore, cryptoexplosion can be ascribed as the most primary mechanism of earthquake generation.

Response to: Comment on “New simulations and understanding of the 1908 Messina tsunami for a dual seismic and deep submarine mass failure source” by L. Schambach, S.T. Grilli, D.R. Tappin, M.D. Gangemi, G. Barbaro [Marine Geology 421 (2020) 106093

In this response, we address and refute the comments made by Argnani (2021) on our 1908 Messina tsunami paper (Schambach et al., 2020), regarding the poor geological constraints underpinning the numerical tsunami modeling. Earthquake mechanisms can be constructed from ‘geology’, but because ruptures are usually blind, seabed evidence may be absent. Alternatively, with small magnitude earthquakes, such as Messina 1908, the small vertical displacements may not be resolved on seismic or multibeam echosounder bathymetric records, because of the relatively low frequencies of the recording equipment. Hence, for earthquake tsunami, seismological data may be more appropriate as the basis for numerical modeling. With regard to submarine mass failure, when interpreting seismic and bathymetry data, the frequency content should again be carefully considered, because smaller features may not be resolved. Regarding the 1908 tsunami, the Mw 7.1 earthquake magnitude would not be expected to generate the recorded tsunami runups for the 5 sources we modeled, as is proved from our modeling; this would also be the case for the Barreca et al. (2021) source proposed in the discussion. Combined with any of these earthquake sources, the submarine mass failure we identified and mapped, however, in large part does. The evidence most critical to the age dating of our identified SMF, presented as too old in the discussion, is that: (i) it is at the location predicted by the inverse wave ray tracing based on tsunami arrival observations; and (ii) upon forward modeling, this tsunami mechanism generates the onland tsunami record.

THE CURRENT STRESS OF EARTH'S CRUST IN THE TERRITORY OF UZBEKISTAN ACCORDING TO FOCAL EARTHQUAKE MECHANISMS

The current stress of Earth's crust in the territory of Uzbekistan has been studied using a focal earthquake mechanisms catalogue that includes the data provided by many authors. Stress reconstructions are based on the cataclastic analysis of displacements along fractures. For reconstructing the stress state at different depths of the crust in several seismically active regions of the study area, we consider a minimum number of earthquakes in a homogeneous sample equal to 6 and an averaging radius of 10 to 30 km within a single domain. The azimuths and dip angles of the principal stress axes, Lode – Nadai coefficients, geodynamic types of stress modes, relative (normalized to rock strength) values of maximum shear stresses, and effective pressure values are determined. Maps showing the spatial distribution of the studied parameters are constructed for both the entire seismically active layer and the depth layers. Stress fields are reconstructed and compared at two hierarchical levels based on the parameters of focal mechanisms of weak and moderate earthquakes (М≤4.5) and those of strong (М≥5.0) earthquakes. "Tectonic Stresses of Eurasia", the Internet resource created by IPE RAS, is used to visualize the stress field reconstructed from the data on strong (М≥5.0) earthquakes.

Differential Interferometric Synthetic Aperture Radar data for more accurate earthquake catalogs

The accuracy of earthquake catalogs limits the reliability of earthquake hazard assessment and the comprehensive understanding of earthquake mechanisms. Current seismic catalogs are based on the inversion of seismic wave data. The accuracy of their source parameters, which reflect the quantity and layout of seismic stations, and the crustal velocity model used, are often highly uncertain. The open source and popularization of Interferometric Synthetic Aperture Radar (InSAR) deformation data offer the potential to provide more accurate source parameters for earthquake catalogs. In this study, we used same-source InSAR data and a consistent processing approach (i.e., the same sampling, inversion algorithm, and processing flow) to obtain the fault slip models and source parameters of 56 earthquakes, covering most of earthquakes observed by the Sentinel-1 since 2014; these were then used to form a unified InSAR earthquake catalog (U-InSAR). We then compiled a second InSAR earthquake catalog (C-InSAR) based on the source parameters of an additional 164 earthquakes inverted using InSAR deformation data from various sources by previous studies, among which 45 earthquakes included additional Global Navigation Satellite System (GNSS) data. The C-InSAR catalog was used to evaluate the impact of data sources and processing approach on the consistency of InSAR catalogs; we found no significant differences between the U- and C-InSAR catalogs. Secondly, the combined U- and C-InSAR catalogs were compared with seismological catalogs, and showed significantly improved seismic source locations, depths, moment magnitudes, fault strikes, fault dips, and fault rakes. Our results confirm the rationality and feasibility of constructing earthquake catalogs using source parameters from a variety of InSAR data sources and inversion algorithms. We emphasize that InSAR catalogs can provide an important supplement, improvement, and/or correction to seismological catalogs, and can provide important basic data for more refined and reliable research on earthquake mechanisms and hazard assessments. Finally, we set up a preliminary sharing and distribution system for InSAR-based catalogs.

Estimation of the orientation of stress in the Earth\u2019s crust without earthquake or borehole data

Mechanical stress acting in the Earth’s crust is a fundamental property that is important for a wide range of scientific and engineering applications. The orientation of maximum horizontal compressive stress can be estimated by inverting earthquake source mechanisms and measured directly from borehole-based measurements, but large regions of the continents have few or no observations. Here we present an approach to determine the orientation of maximum horizontal compressive stress by measuring stress-induced anisotropy of nonlinear susceptibility, which is the derivative of elastic modulus with respect to strain. Laboratory and Earth experiments show that nonlinear susceptibility is azimuthally dependent in an anisotropic stress field and is maximum in the orientation of maximum horizontal compressive stress. We observe this behavior in the Earth—in Oklahoma and New Mexico, U.S.A, where maximum nonlinear susceptibility coincides with the orientation of maximum horizontal compressive stress measured using traditional methods. Our measurements use empirical Green’s functions and solid-earth tides and can be applied at different temporal and spatial scales.

Article 8. The formation mechanism and forecasting of earthquakes

Article 8. The formation mechanism and forecasting of earthquakes

Inhomogeneous precursor characteristics of rock with prefabricated cracks before fracture and its implication for earthquake monitoring

Abstract. Earthquake precursors and earthquake monitoring are always important in the earthquake research field, even if there is still debate about the existence of earthquake precursors. However, it is extremely difficult to observe the seismogenic environment of earthquakes directly. Laboratory rupture experiment is a useful technique to simulate and gain an insight into the complex mechanisms of earthquakes. Five marble samples with prefabricated cracks are used for uniaxial loading experiments to investigate whether there is a precursory signal before rock fracture and to simulate the rupture process of strike-slip fault. The existence of a precursory signal is confirmed by the coefficient of variation (CV) results, from which we can see two patterns which are known as seismicity acceleration and quiescence before an earthquake. Moreover, these CV findings are applied to determine the locations of large deformation sampling points on the rock surface at different loading stages. Similar results are obtained when we consider actual seismicity at the northern end of the San Andreas Fault in California, which provides crucial evidence to prove the existence of precursor characteristics. In this case, three kinds of seismic monitoring models are designed to find out how to monitor these characteristics more effectively.

Deep Dehydration as a Plausible Mechanism of the 2013 Mw 8.3 Sea of Okhotsk Deep-Focus Earthquake

The rupture mechanisms of deep-focus (>300 km) earthquakes in subducting slabs of oceanic lithosphere are not well understood and different from brittle failure associated with shallow (<70 km) earthquakes. Here, we argue that dehydration embrittlement, often invoked as a mechanism for intermediate-depth earthquakes, is a plausible alternative model for this deep earthquake. Our argument is based upon the orientation and size of the plane that ruptured during the deep, 2013 Mw 8.3 Sea of Okhotsk earthquake, its rupture velocity and radiation efficiency, as well as diverse evidence of water subducting as deep as the transition zone and below. The rupture process of this earthquake has been inferred from back-projecting dual-band seismograms recorded at hundreds of seismic stations in North America and Europe, as well as by fittingP-wave trains recorded at dozens of globally distributed stations. If our inferences are correct, the entirety of the subducting Pacific lithosphere cannot be completely dry at deep, transition-zone depths, and other deep-focus earthquakes may also be associated with deep dehydration reactions.

Seismogenic Faults of the Changning Earthquake Sequence Constrained by High-Resolution Seismic Profiles in the Southwestern Sichuan Basin, China

Abstract The seismicity rate in the southwestern Sichuan basin, China, dramatically increased after 2014. The associated moderate earthquakes may have been induced by salt mining or shale gas exploration. The location of the seismogenic faults causing these moderate earthquakes has not been confirmed, resulting in a lack of understanding of the earthquake mechanisms in the study area. The detailed structural characteristics of pre-existing faults, which are typically responsible for induced seismicity, are unclear. In this study, we used high-resolution seismic reflection profiles in conjunction with geological, seismologic, and geodetic data to reveal the 3D distributions of the seismogenic faults. Basement thrust faults in the Changning anticline were identified using seismic interpretations and are associated with the 2019 Changning earthquake sequence. The geometry and location of these pre-existing faults are consistent with previous studies of the seismology and structural geology in the area. The well-developed pre-existing fault system in the sedimentary cover and basement makes the Changning area vulnerable to induced earthquakes. Present-day reactivation of the basement fault system reveals the unstable state of the local tectonic stress field. It is possible that the potential seismic risk in this region could be increased by industrial activity in the southwestern Sichuan basin.

Present-day geodynamics of the Western Alps: new insights from earthquake mechanisms

Abstract. Due to the low to moderate seismicity of the European Western Alps, few focal mechanisms are available in this region to this day, and the corresponding current seismic stress and strain fields remain partly elusive. The development of dense seismic networks in past decades now provides a substantial number of seismic records in the 0–5 magnitude range. The corresponding data, while challenging to handle due to their amount and relative noise, represent a new opportunity to increase the spatial resolution of seismic deformation fields. The aim of this paper is to quantitatively assess the current seismic stress and strain fields within the Western Alps, from a probabilistic standpoint, using new seismotectonic data. The dataset comprises more than 30 000 earthquakes recorded by dense seismic networks between 1989 and 2013 and more than 2200 newly computed focal mechanisms in a consistent manner. The global distribution of P and T axis plunges confirms a majority of transcurrent focal mechanisms in the entire western Alpine realm, combined with pure extension localized in the core of the belt. We inverted this new set of focal mechanisms through several strategies, including a seismotectonic zoning scheme and grid procedure, revealing extensional axes oriented obliquely to the strike of the belt. The Bayesian inversion of this new dataset of focal mechanisms provides a probabilistic continuous map of the style of seismic deformation in the Western Alps. Extension is found to be clustered, instead of continuous, along the backbone of the belt. Robust indications for compression are only observed at the boundary between the Adriatic and Eurasian plates. Short-wavelength spatial variations of the seismic deformation are consistent with surface horizontal Global Navigation Satellite System (GNSS) measurements, as well as with deep lithospheric structures, thereby providing new elements with which to understand the current 3D dynamics of the belt. We interpret the ongoing seismotectonic and kinematic regimes as being controlled by the joint effects of far-field forces – imposed by the anticlockwise rotation of Adria with respect to Europe – and buoyancy forces in the core of the belt, which together explain the short-wavelength patches of extension and marginal compression overprinted on an overall transcurrent tectonic regime.

The Horseshoe Abyssal plain Thrust could be the source of the 1755 Lisbon earthquake and tsunami

The southwest Iberia margin is widely believed to have hosted the 1755 Great Lisbon earthquake and ensuing tsunami, one of the most destructive natural events in European history. Here we combine geophysical data and numerical tsunami modelling to investigate the source and mechanism responsible for this event. We find that an intra-plate, lithospheric¬-scale thrust fault located at the Horseshoe Abyssal Plain coincides with the location and focal mechanisms of the largest regional earthquakes and is likely to have suitable dimensions and fault-rock properties to account for the magnitude of the 1755 event. We present tsunami simulations with this fault as the source, and find that they reproduce reported tsunami energy propagation patterns, arrival-times and run up heights more successfully than other modelled sources. We propose that a reverse dip-slip mechanism on the northwest verging Horseshoe Abyssal plain Thrust, combined with the two-state mechanical behaviour of serpentinite, is the most likely candidate for the source of the 1755 Great Lisbon earthquake and for other recent large regional earthquakes.

The inferences on the Aegean geodynamic context from 30 October 2020 Samos earthquake (Mw:6.8)

On October 30, 2020, an earthquake with a magnitude of 6.8 (Mw) struck the northern coast of Samos Island in the Kuşadası Gulf. The solution to the focal mechanism indicates that the earthquake of 30 October 2020 occurred on a normal fault with nodal planes of E-W strike; thus, indicating extension in N-S direction. The fault plane solutions show a N-S trending extension for normal faults, which are obtained by inverting the moment tensor waveforms of 23 earthquakes and the P-wave first motion polarities of 11 aftershocks. A normal fault stress regime of approximately N-S (N6°E) σ3 axis is given by the inversion of slip vectors measured at sites located on land in Kuşadası. The mean R value is 0.84, suggesting that the stress regime is triaxial extensional stress state. The inversion of the focal mechanism of earthquakes occurring on land and in the Gulf of Kuşadası describes an extensional stress regime active today, characterized by an approximately N-S (N9°E) σ3 axis. The calculated R value of 0.31 indicates a triaxial stress state. For the 30 October 2020 earthquake (Mw:6.8), the Coulomb failure stress change analysis shows a substantial reduction in stress in the N-S direction supporting the kinematic results. The N-S extension in Western Anatolia-Aegean is largely influenced by the relatively fast movement of the Hellenic trench southwards, related to the sinking of the African plate beneath Aegean.

Structure of the northwestern North Anatolian Fault Zone imaged via teleseismic scattering tomography

SUMMARYInformation on fault zone structure is essential for our understanding of earthquake mechanics, continental deformation and seismic hazard. We use the scattered seismic wavefield to study the subsurface structure of the North Anatolian Fault Zone (NAFZ) in the region of the 1999 İzmit and Düzce ruptures using data from an 18-month dense deployment of seismometers with a nominal station spacing of 7 km. Using the forward- and back-scattered energy that follows the direct P-wave arrival from teleseismic earthquakes, we apply a scattered wave inversion approach and are able to resolve changes in lithospheric structure on a scale of 10 km or less in an area of about 130 km by 100 km across the NAFZ. We find several crustal interfaces that are laterally incoherent beneath the surface strands of the NAFZ and evidence for contrasting crustal structures either side of the NAFZ, consistent with the presence of juxtaposed crustal blocks and ancient suture zones. Although the two strands of the NAFZ in the study region strike roughly east–west, we detect strong variations in structure both north–south, across boundaries of the major blocks, and east–west, parallel to the strike of the NAFZ. The surface expression of the two strands of the NAFZ is coincident with changes on main interfaces and interface terminations throughout the crust and into the upper mantle in the tomographic sections. We show that a dense passive network of seismometers is able to capture information from the scattered seismic wavefield and, using a tomographic approach, to resolve the fine scale structure of crust and lithospheric mantle even in geologically complex regions. Our results show that major shear zones exist beneath the NAFZ throughout the crust and into the lithospheric mantle, suggesting a strong coupling of strain at these depths.

Rupture Kinematics of the 11 January 2021 Mw 6.7 Hovsgol, Mongolia, Earthquake and Implications in the Western Baikal Rift Zone

AbstractThe Mongolia plateau is the farthest intracontinental region of the India–Eurasia collision and is a transition zone between north–south convergence to the south in the Tien Shan and northwest–southeast extension to the north in the Baikal rift. Mongolia has experienced four M 8 earthquakes since 1905, but due to limited observations, the mechanism of these strong earthquakes and regional tectonics are poorly understood. The 11 January 2021 Mw 6.7 Hovsgol, Mongolia, earthquake is the largest event that has occurred in the Hovsgol graben, which is noted for being the northernmost convergence region of the India–Eurasia collision and the youngest extension region of the Baikal rift. In this article, the coseismic displacements are retrieved by space geodesy for the first time in this region, providing good constraints for the deformation pattern. We use a finite-fault inversion of InSAR and teleseismic data, and a backprojection analysis to reveal the rupture kinematics of this event. The geometry of the Hovsgol fault is determined as east-dipping with a dip of 45°. The rupture process is characterized by a northwestward propagation with a moderate average rupture velocity of ∼2.0 km/s and a complex slip pattern composed of two major slip patches with dimensions of 40 km×20 km. The oblique slip, illustrated by predominate extension and significant dextral striking, confirms the right-lateral-striking faulting in the Hovsgol rift, which indicates that the eastwardly north–south convergence across the southwest segment of the Baikal rift has decreased.

Machine Learning Predicts the Timing and Shear Stress Evolution of Lab Earthquakes Using Active Seismic Monitoring of Fault Zone Processes.

Machine learning (ML) techniques have become increasingly important in seismology and earthquake science. Lab‐based studies have used acoustic emission data to predict time‐to‐failure and stress state, and in a few cases, the same approach has been used for field data. However, the underlying physical mechanisms that allow lab earthquake prediction and seismic forecasting remain poorly resolved. Here, we address this knowledge gap by coupling active‐source seismic data, which probe asperity‐scale processes, with ML methods. We show that elastic waves passing through the lab fault zone contain information that can predict the full spectrum of labquakes from slow slip instabilities to highly aperiodic events. The ML methods utilize systematic changes in P‐wave amplitude and velocity to accurately predict the timing and shear stress during labquakes. The ML predictions improve in accuracy closer to fault failure, demonstrating that the predictive power of the ultrasonic signals improves as the fault approaches failure. Our results demonstrate that the relationship between the ultrasonic parameters and fault slip rate, and in turn, the systematically evolving real area of contact and asperity stiffness allow the gradient boosting algorithm to “learn” about the state of the fault and its proximity to failure. Broadly, our results demonstrate the utility of physics‐informed ML in forecasting the imminence of fault slip at the laboratory scale, which may have important implications for earthquake mechanics in nature.

Penentuan Karakteristik Mekanisme Gempa Tahun 2018-2019 Di Nusa Tenggara Menggunakan Metode Inversi Momen Tensor

Nusa Tenggara is one of the areas with a high level of seismic activity in Indonesia because this area is located between the Indian Ocean plate, which moves northward and pushes the Eurasian plate. One method that is often used to determine an earthquake's epicentre is the Tensor Moment Inversion method. This study aims to determine the moment tensor magnitude of each earthquake event and determine earthquake characteristics based on the earthquake focus mechanism in Nusa Tenggara from 2018 to 2019. The earthquake with a magnitude of ≥ 5.7 SR and to find out the fault parameters, namely strike, dip, and rake using waveform data. One method that is often used to determine an earthquake's epicentre is the Tensor Moment Inversion method. The results showed that the fault planes formed were reverse faults and oblique faults. It has been calculated the moment tensor for each of the six components, namely Mxx, Myy, Mzz, Mxy, Myz and Mxz. From the results of the focal analysis of the 2018-2019 Nusa Tenggara earthquake mechanism, the values of the fault plane orientation parameters such as strike, dip and rake are obtained. For strikes in Nusa Tenggara on area 1, namely: 73° to 122°, Dip: 20° to 72° and Rake: 53° to 139°. While in field 2 for a strike, it is 232° to 280°, Dip 28° to 75°, Rake: 52° to 102°.