Strong Historical Earthquakes Research Articles

Deep Blind Fault Activity—A Fault Model of Strong Mw 5.5 Earthquake Seismogenic Structures in North China

North China is one of the high-risk areas for destructive and strong earthquakes in mainland China and has experienced numerous strong historical earthquakes. An earthquake of magnitude MW 5.5 struck Pingyuan County, Dezhou city, in Shandong Province, China, on 6 August 2023. This earthquake was the strongest in the eastern North China Craton since the 1976 Tangshan earthquake. Since the earthquake did not produce surface ruptures, the seismogenic structure for fault responsible for the Pingyuan MW 5.5 earthquake is still unclear. To reveal the subsurface geological structure near the earthquake epicenter, this study used high-resolution two-dimensional (2D) seismic reflection profiles and constructed a three-dimensional (3D) geometric model of the Tuqiao Fault by interpreting the faults in the seismic reflection profiles. This study further combined focal mechanism solutions, aftershock clusters, and other seismological data to discuss the seismogenic fault of the Pingyuan MW 5.5 earthquake. The results show that the Tuqiao Fault is not the seismogenic fault of the MW 5.5 earthquake. The actual seismogenic structure may be related to the NE-oriented high-angle strike-slip blind fault developed in the basement. We further propose three possible fault models for the strong seismogenic structure in North China to discuss the potential seismotectonics in this region.

The earthquake probabilities of the Liupanshan fault zone based on the Coulomb stress and friction constitutive law

As the forefront of the northeastern margin of the Tibetan Plateau, the Liupanshan area is subjected to significant Cenozoic deformation. Considering the background of historical earthquakes and the current seismic activity, the Liupanshan fault poses a risk of strong earthquakes. This paper analyzes the evolution of Coulomb stress induced by the coseismic and postseismic viscoelastic deformation of six historical strong earthquakes that occurred around the Liupanshan area since the twentieth century. Additionally, based on the disturbance in Coulomb stress and the background seismicity rate, the probability of earthquake occurrence is quantitatively evaluated using the frictional constitutive law. The results indicate that northern section of the Liupanshan fault has higher earthquake potential than the southern section, warranting close attention. These findings serve as a reference for medium- and long-term earthquake forecast and risk assessment in the vicinity of the Liupanshan fault.

Source parameter inversion of the 2021 MW7.4 Maduo earthquake and stress transfer in the eastern Bayan Har block

In order to explore the constraint degree of GNSS and InSAR data on the Maduo earthquake under the layered earth model structure, and to understand the cause of the Maduo earthquake and the danger of the surrounding area, this paper uses D-InSAR technology to obtain the InSAR co-seismic deformation field of the Maduo earthquake on May 22,2021. Based on GNSS and InSAR data, the co-seismic slip model and fault plane stress distribution of the Maduo earthquake are jointly inverted. This paper calculates the Coulomb stress changes caused by 14 M ≥ 7 strong earthquakes co-seismic, post-seismic viscoelastic relaxation and inter-seismic tectonic stress loading of 19 fault segments in the Bayan Har block research area (96°E-106°E, 29°N-36°N) since 1900. The results show that: (1) The maximum Line Of Sight (LOS) deformation obtained based on the ascending and descending InSAR data was about 0.9 m. The maximum slip amount of GNSS + InSAR joint inversion is 4.87 m, which is located in the Dongcao Along Lake section (∼98.6°E). Combined with the stress drop distribution of the fault surface, it is found that the Maduo earthquake is dominated by strike-slip. (2) The historical strong earthquakes delayed the Maduo earthquake by nearly 103 years. The 1937 Huashixia earthquake, the 1947 Dari earthquake, the 1963 Dulan earthquake, and the 1973 Luhuo earthquake had the greatest stress unloading effect, which was equivalent to delaying the Maduo earthquake by 53 years, 21 years, 11 years, and 17 years, respectively. The cumulative Coulomb stress at the source location of the Maduo earthquake reached 0.0112 MPa. Most area of the fault sections such as the East Kunlun Fault, the Maduo-Gande Fault, the western and eastern sections of the Dari Fault, the western and eastern sections of the Qingshuihe Fault, the Ganzi-Yushu Fault, and the eastern section of the Kunlunshankou-Jiangcuo Fault are in the Coulomb stress loading area, which should be paid attention to.

Strong historical earthquakes around Osh city, Kyrgyzstan

This paper presents data on strong earthquakes that occurred in the area around Osh city from various literature sources. The information on strong earthquakes of the past has been compiled on the basis of historical data. The catalog of strong earthquakes is given in the radius of 60 km from Osh city. A description of macroseismic data of these earthquakes is given.

Several strong historical earthquakes during Ming and Qing Dynasties and their effects to local reconstruction at Southern Shanxi Province, North China: Insight from the Chinese literature

The dissection of related Chinese literature of historical strong earthquakes is very important for formulating effective disaster mitigation measures. During the Ming and Qing Dynasties (AD 1368–1910) in North China, there were three strong earthquakes (AD 1556 Huaxian M 8.25 earthquake, AD 1695 Linfen M 7.75 earthquake and AD 1815 Pinglu M 6.75 earthquake), caused great damages to local cities of southern Shanxi Province, including damages of various types of buildings, numerous casualties, while the society and economy suffered a sudden heavy blow. Meanwhile, the occurrence of these earthquakes also provides important opportunities to restore the regional social order. In addition to the support of national disaster relief policies, the local officials actively organized people to cope with the disasters, made every effort to reconstruct the cities, that reflected the feelings of "caring about People's livelihood" or "the principle of supremacy of life", to improve the efficiency of regional social order benign operation. Certainly, the recovery and reconstruction process after the three strong earthquakes reflected imbalance between different time, regions, and between urban and rural areas. The literature review in this article has certain reference significance for the formulation and improvement of current disaster reduction measures.

Seismotectonic role of transversal structures in the Plio-Quaternary evolution of the external Marche Apennines (Italy)

We defined the seismotectonic setting of the external Marche Apennines (central Italy) by integrating geomorphological, structural and seismological data. The area is characterized by strong historical earthquakes, but the geometries and kinematics of the seismogenic sources have not previously been well defined. Plio-Quaternary Apennine compressional NW–SE structures are segmented by NE–SW-oriented transversal faults, the origin and role of which are still debated. We characterized the geometry, kinematics and activity of the four main transversal faults to better define their seismogenic potential. These high-angle, deeply rooted transversal fault systems have been mapped and separate the external Apennine sector into blocks and sub-blocks with different structural and evolutionary features. The integrated dataset showed that some inherited fault segments have recently been reactivated, displacing Quaternary deposits. The spatial distribution of seismicity indicates that some clusters of hypocentres are located within the basement. Stress field analysis using available focal mechanism solutions confirms the prevalence of left-lateral kinematics on roughly SW–NE-oriented structures. The transversal structures thus contribute to the longitudinal segmentation of the Apennine structures and, more generally, are involved in the northern part of the Adria plate kinematics towards the north and NNW. The assessment of seismic hazards and planning to mitigate risks in populated areas close to the Adriatic coast should consider these potentially active faults evidenced by instrumental seismicity and important historical earthquakes.

Stress triggering effect on the 2022 Honghe MS5.0 earthquake with historical strong earthquakes

The 2022 Honghe MS5.0 seismic event is intriguing due to its occurrence in the south of the Red River Fault, an area historically lacking seismic activities greater than MS5.0. To elucidate the seismogenic mechanism and scrutinize stress-triggered interactions, we calculated co-seismic and post-seismic Coulomb stress alterations induced by nine historical seismic events (M ≥ 6.0). The analysis reveals that these substantial seismic events provoked co-seismic stress augmentations of 1.409 bar and post-seismic stress increments of 0.159 bar. Noteworthy seismic events, such as the 1833 Songming, 1877 Shiping, 1913 Eshan, and 1970 Tonghai earthquakes, catalyzed the occurrence of the Honghe earthquake. Areas of heightened future seismic risk include the southern region of the Red River Fault and the eastern segments of the Shiping-Jianshui and Qujiang faults. Additionally, we assessed the correlation between the spatial distribution of aftershocks and the Coulomb stress shift triggered by the mainshock, taking into account the influence of calculation parameter settings.

Reappraisal of Data of Hydrological Changes Associated with Some Strong Historical Italian Earthquakes

Historical seismology retrieves information about the effects of earthquakes that occurred in the past, mostly regarding the damage, but also on environmental effects. In this paper, we describe the methodology of our research on earthquake-induced hydrological effects, which have been long observed and documented, and are among the most outstanding coseismic phenomena. The method of research follows two distinct paths, depending on whether the investigated event occurred before or after the end of the 18th Century. For the most ancient events, we present examples of historical accounts, local reports, private letters, and diaries, in which the information of interest is often hidden within broader descriptions and mentioned as a minor curiosity. On the contrary, for more recent earthquakes, the research benefits from the growing interest in naturalistic observations that marked the onset of the 19th Century, and is achieved through detailed descriptions, journals, seismic postcards, and through the first systematic collections of instrumental data. Finally, we describe a possible method of classification of the hydrological data and show an analysis of the potential applications and outcomes of this type of research.

A Potential Earthquake with Magnitude Mw 7.2 on the Northern Xiaojiang Fault Revealed by GNSS Measurement

We used near-field and regional GNSS (Global Navigation Satellite System) data to quantify the deformation and locking ratio of the Xiaojiang fault (XJF) in southeastern Tibet. The inversion based on the dislocation model shows that the slip rate of the XJF is 9–11 mm/a; the locking depths of the northern, central, and southern segments are 25.5 km, 12 km, and 22.5 km, respectively. The inversion with DEFNODE program shows that the locking of the northern segment is the strongest above a depth of 20 km, while the locking between 20 km and 26 km is intermediate, and the weakest locking is found below 26 km. In the central segment, the depths of the interface are 6 km and 12 km. Additionally, a locked asperity that has the potential of generating an Mw 7.2 earthquake along the northern segment is delineated. The asperity and the shallow locking zone are basically consistent with the rupture area of the 1733 M 7.8 Dongchuan earthquake and the 1833 M 8 Songming earthquake, respectively. Both the activity of the historical strong earthquakes and the seismicity of the microearthquakes recorded over recent years seem to suggest that a potential earthquake is imminent.

Stress evolution on major faults in Tien Shan and implications for seismic hazard

Tien Shan tectonic belt has experienced intense seismicity and a series of destructive strong earthquakes. However, earthquake triggering effects and faulting interactions in this area are poorly understood. A 3D finite element model of Tien Shan tectonic belt is constructed, to investigate stress evolutions on major faulting zones driven by interseismic tectonic loading and historical strong earthquakes with M≥ 6.0 since 1900. The numerical results show Tien Shan is dominated by nearly N-S compression, with higher tectonic loading rate in southwest Tien Shan. 1906 Manas M7.7 earthquake exerted pronounced Coulomb stress increase on its adjacent faulting zones, especially in the epicenter of 2016 Hutubi M6.0 earthquake. And three large earthquakes with M≥ 8.0, e.g., Chilik M8.3 earthquake in 1889, Kemin M8.0 earthquake in 1911 and Atushi M8.2 earthquake in 1902, increased the Coulomb stress by above 100 kPa in the epicenter of 1991 Keping M6.0 earthquake. While, stress perturbations by other strong earthquakes are limited, with slight Coulomb stress changes in the epicenters of their subsequent earthquakes. Overall, strong earthquakes with M> 7.0 in Tien Shan, induced substantial Coulomb stress changes on the adjacent faulting zones. Stress evolutions on major faults reveal higher stress accumulation in southwest Tien Shan, east KQX fault, west BoA fault, and HMT fault, indicating higher seismic risk.

Strong historical earthquakes and their relationships with the Tan-Lu fault system and modern seismicity in eastern China

The largest earthquake (Ms 8½) in eastern China occurred near Tancheng in 1668. Six M ≥ 6 earthquakes occurred in this region in historical time. We re-examine the primary historical archives from this region, adding independent constraints such as maps of active faults, local topography, intensity attenuation laws for China, and relevant administrative practices in archiving data, to reassess source parameters (epicenter, magnitude, or maximum intensity). We use the seismic density index—a measure of the clustering of seismicity weighted by source magnitude—to identify candidate zones of present-day clustering of seismicity than may represent a long-term memory of past historical events in an intraplate setting. We update at least one of the source parameters for four of the seven events. The main shock and two aftershocks of the 1668–1672 Ms 8½ Tancheng earthquake sequence locate along the strike of the Tan-Lu fault zone, each associated with significant and contiguous seismic density anomalies whose elliptical contours are elongated along its strike. A third major aftershock (Ms ≈ 6) in this sequence locates some 200 km away from the fault zone. Six of the seven historical events have seismic density anomalies that cannot be explained by aftershocks of modern seismicity (ML ≤ 5.3), and hence are candidate zones for long-lived aftershock sequences. In contrast, there are no significant seismic density anomalies along the section of Tan-Lu fault south of Suqian, despite palaeo-seismic evidence for a Ms 8½ earthquake around 6280 B.C., providing an upper bound to long-term memory of great earthquakes in this region.

Transtensional coseismic fault slip of the 2021 Mw 6.7 Turt Earthquake and heterogeneous tectonic stress surrounding the Hovsgol Basin, Northwest Mongolia

Knowledge of the regional crustal deformation and stress field is fundamental to understanding and constrain the ongoing evolution of Hovsgol basin, northwest Mongolia. The 2021 Mw 6.7 Turt earthquake provides an unprecedented opportunity to probe the local tectonic stress field and upper crust deformation. We investigate the coseismic surface displacements and invert fault slip models using Interferometric Synthetic Aperture Radar observations and teleseismic data. The mainshock occurred as a result of normal faulting with a right-lateral strike-slip component on an NW striking plane, which is consistent with the transtensive local stress field inverted from regional focal mechanisms. It is surrounded by transpressive and strike-slip stress fields proposed by previous studies indicating regional stress heterogeneity probably controlled by the distinct structure geometries in and around Hovsgol basin. Our results also suggest that the current deformation of the Hovsgol basin is dominated by half-graben forming. Seven historical strong earthquakes (M 7) may advance the 2021 Turt earthquake by ~12% recurrence interval, based on the assumption of equal stress release from recurrence earthquakes, meanwhile, the 2021 Turt earthquake may increase the potential seismic hazard on the neighbor Mondy and South Hovsgol faults, which deserves more attention.

Coseismic Displacement and Slip Distribution of the 21 May 2021 Mw 6.1 Earthquake in Yangbi, China Derived From InSAR Observations

On 21 May 2021, a Mw 6.1 earthquake struck Yangbi County, Yunnan Province, China. In this study, InSAR data from Sentinel-1 SAR images were processed to image the coseismic deformation fields of the Yangbi earthquake. Then, the optimal slip model was obtained by applying the particle swarm optimization method. The interferometry results revealed that the earthquake triggered obvious surface deformation near the epicenter, while the earthquake did not produce an obvious surface rupture zone from field investigation. The optimal slip model suggests that the strike of the seismogenic fault responsible for this event is 139°, the dip angle is 81°, and the average rake angle is -170°. Additionally, the slip was concentrated mainly at depths of 2–8 km, the maximum dip-slip amount was 0.5 m, and the cumulative seismic moment reached 1.43 × 1018 N⋅m, equivalent to a Mw 6.1 earthquake. The geodetic and geophysical inversion results demonstrate that the Yangbi earthquake was dominated by a steeply dipping dextral strike-slip rupture. The rupture fault generally strikes NNW-SSE, which is consistent with that of the Weixi-Qiaohou fault, and may be a relatively new fault formed by an E-W-oriented extension of the western boundary of the Sichuan-Yunnan block. Finally, based on the InSAR results in combination with the spatial distribution characteristics of ground fissures and the strong historical earthquakes, we analyzed the tectonic background preceding the Yangbi earthquake and analyzed the relationship between the Yangbi earthquake and strong historical earthquakes in the region, thereby providing empirical evidence for analyzing seismic risk and fault rupture parameters, interpreting seismic deformation characteristics, and better understanding the seismogenic background of the western boundary of the Sichuan-Yunnan block.

Pliocene–Quaternary seismogenic faults in the inner Northern Apennines (Valdelsa Basin, southern Tuscany) and their role in controlling the local seismicity

AbstractPliocene–Quaternary faults are relevant structures with which to constrain the seismotectonic context and contribute to the evaluation of the seismic hazard of a region. Many of these faults, however, do not show clear surface evidence even when releasing earthquakes. For these reasons they can be extremely dangerous as they receive relatively little attention and can be difficult to identify. From among the various surface geology studies and/or palaeoseismological investigations, we focus our attention on the integration of different datasets such as seismic reflection profiles, surface kinematic data and the relocation of seismological data, which make it possible to identify and characterize active faults whose dimension and earthquake potential would otherwise not be large enough to make them identifiable. We take as an example the Montespertoli NE-trending fault in southern Tuscany (central Italy) with which we associate the 2016 M=3.9 Castelfiorentino earthquake. This structure is part of a wider (in the order of 15–20 km) crustal-scale shear zone, which may be responsible for strong historical earthquakes in the area.

Spatiotemporal Distribution of Strong Earthquakes and the Time Course of the Parameters of the Seismic Regime of the Bishkek Seismic Research Site of Kyrgyzstan

This paper analyzes spatiotemporal distribution of strong historical earthquakes within the Bishkek seismic research (BSR) site. The main focus is on the spatial and temporal characteristics of crustal earthquakes in the instrumental period of observation, particularly the last 30 years (1991-2020). This period was the time of transition from the analog earthquake recording system to a digital one. Available epicenter maps of weak to moderate earthquakes were analyzed to identify areas of high and low seismic density. The analysis uses such parameters as the total number of earthquakes, magnitude, slope of the recurrence curve, and total seismic energy. The time course of seismic parameters was the main factor used to assess the current seismic setting of the Bishkek seismic research site. The slope of the earthquake recurrence curve was calculated using two methods: the least squares method and the maximum likelihood method. The analysis identified a downward trend showing a decrease in the number of earthquakes in the past 30 years (1991-2020). The results of this research can help develop a methodology for strong earthquake prediction and seismic hazard assessment of the BSR area.

Fault Geometry and Mechanism of the Mw 5.7 Nakchu Earthquake in Tibet Inferred from InSAR Observations and Stress Measurements

Different types of focal mechanism solutions for the 19 March 2021 Mw 5.7 Nakchu earthquake, Tibet, limit our understanding of this earthquake’s seismogenic mechanism and geodynamic process. In this study, the coseismic deformation field was determined and the geometric parameters of the seismogenic fault were inverted via Interferometric Synthetic Aperture Radar (InSAR) processing of Sentinel-1 data. The inversion results show that the focal mechanism solutions of the Nakchu earthquake are 237°/69°/−70° (strike/dip/rake), indicating that the seismogenic fault is a NEE-trending, NW-dipping fault dominated by the normal faulting with minor sinistral strike-slip components. The regional tectonic stress field derived from the in-situ stress measurements shows that the orientation of maximum principal compressive stress around the epicenter of the Nakchu earthquake is NNE, subparallel to the fault strike, which controlled the dominant normal faulting. The occurrence of seven M ≥ 7.0 historical earthquakes since the M 7.0 Shenza earthquake in 1934 caused a stress increase of 1.16 × 105 Pa at the hypocenter, which significantly advanced the occurrence of the Nakchu earthquake. Based on a comprehensive analysis of stress fields and focal mechanisms of the Nakchu earthquake, we propose that the dominated normal faulting occurs to accommodate the NE-trending compression of the Indian Plate to the Eurasian Plate and the strong historical earthquakes hastened the process. These results provide a theoretical basis for understanding the geometry and mechanics of the seismogenic fault that produced the Nakchu earthquake.

Stress Transfer at the Northeastern End of the Bayan Har Block and Its Implications for Seismic Hazards: Insights From Numerical Simulations

AbstractThe 2021Mw7.4 Maduo earthquake in Qinghai, China, filled the seismic gap in the eastern segment of the northern boundary of the Bayan Har Block, and four otherM > 7 historical strong earthquakes occurred at the northeastern end of the Bayan Har Block within a period of 80 years before the Maduo earthquake. This series of large seismic events provides an excellent example for investigating the stress transfer and fault interactions of strong earthquakes on the continent. In this study, we established a viscoelastic numerical model to calculate the stress transfer before and after the 2021 Maduo earthquake produced by historical earthquakes at the northeastern end of the Bayan Har Block. We found that the Maduo earthquake occurred in the Coulomb stress shadow zone caused by the historical earthquakes, and the 1947 Dari earthquake and the 1937 Tuosuo Lake earthquake jointly delayed the occurrence of the Maduo earthquake. The stress transfer of fiveM > 7 earthquakes to the surrounding faults after 1937 resulted in the segments at both ends of the Dari fault that were unruptured in the 1947 earthquake, the East Kunlun fault zone west of Alan Lake, the Maqin‐Maqu segment of the East Kunlun fault zone, the Longriba fault, the segment of the Ganzi‐Yushu fault south of Yushu, the Minjiang fault, and the northern segment of the Xianshuihe fault being located in the Coulomb stress loading zone. Sustained attention should be paid to the block boundary faults and intra‐block faults with increased seismic hazards.

Focal Mechanism and Tectonic Stress Field of Small Earthquakes in Southwest Margin of Dongting Basin

Based on the broadband seismic waveform data recorded by Hunan digital seismic network, 41 focal mechanism solutions of small earthquakes with M L ≥1.8 in the southwest margin of Dongting Basin from 2009 to 2017 were obtained by integrating the P-wave first-motion and maximum amplitude ratio methods. The parameters of focal mechanism solutions were analyzed using mathematical statistics and systematic cluster analysis. The results showed that the seismic properties in this area are mainly thrust type ( 30/41 ), and the principal compressive stress axis in the focal mechanism solution parameters is NNW and NE, while the tensile stress axis is SSW. Compared to previous studies, the inversion results of the focal mechanism of small earthquakes in the southwest margin of Dongting Basin are in good agreement with the focal mechanism solutions of regional historical strong earthquakes, indicating that the focal mechanism solutions of small earthquakes can represent the regional tectonic stress field in this area.

Strong earthquakes in Azerbaijan for historical and contemporary periods (conceptual review)

Based on the results of the study of literary and archival primary sources, the paper clarifies the available information about catastrophic and destructive earthquakes in Azerbaijan for the historical period with a magnitude of M≥6. Among the strong historical earthquakes in Azerbaijan there are the following: earthquakes in 427, the Ganja (Goygol in 1139), the Ganja in 1235, the East Caucasian in 1667 (± 1 year), the Mashtaga (1842), numerous Shamakhi earthquakes (1192, 1667, 1668, 1669, 1828, 1859, 1868, 1872, 1902), Ardebil (1924), Lankaran (1913), Caspian earthquakes (957, 1812, 1842, 1852, 1911, 1935, 1961, 1963, 1986, 1989, 2000), which caused both changes in the relief of the Earth’s surface, and the destruction of buildings and numerous human casualties. The background seismicity was investigated based on the results of continuous instrumental observations for the period 1902—2019. Seismic processes are unevenly distributed on the territory of Azerbaijan. Existing catalogs of seismic events have been investigated. The behavioral changes in seismicity parameters have been studied. An overview conceptual analysis of two main methods for assessing seismic hazard is given: probabilistic and deterministic, which have found their wide application in recent decades. In conclusion, the most important and general tasks of future seismological studies are emphasized, which are to be performed in the next decades.

Using Google Earth Images to Extract Dense Landslides Induced by Historical Earthquakes at the Southwest of Ordos, China

As historical earthquake records are simple, determining the source parameters of historical strong earthquakes over an extended period is difficult. There are numerous uncertainties in the study of historical earthquakes based on limited literature records. Co-seismic landslide interpretation combined with historical documents can yield the possibility of reducing these uncertainties. The dense co-seismic landslides can be preserved for hundreds to thousands of years in Loess Plateau, North China; furthermore, there are notable attribute differences between earthquake landslides and rainfall-triggered landslides. Along the southwestern margin of the Ordos Block, only one severe earthquake has been recorded in the past 3,000 years. The records of “Sanchuan exhaustion and Qishan collapse” provide clues for an investigation of the 780 BC Qishan earthquake. In this study, combined with historical documents, current high-resolution Google Earth images were used to extract historical landslides along the southwestern of the Ordos Block. There were 6,876 landslides with a total area of 643 km2. The landslide-intensive areas were mainly distributed along the Longxian–Qishan–Mazhao Fault in the loess valley area on the northeastern side of the fault. Loess tableland and river terraces occur on the southwest side of the fault; dense landslides have not been examined due to the topographical conditions in this area. By analyzing the spatial distribution of historical earthquake damage in this region, comparing the characteristics of rainfall-triggered landslides, and combining existing dating results for bedrock collapse and loess landslides, the interpretation of dense historical landslides can be linked to the Qishan Earthquake. The interpretation results are associated with historical records. Analyses of current earthquake cases show that the distribution of dense landslides triggered by strong earthquakes can indicate the episeismic area of an earthquake. In addition, the non-integrated landslide catalog without small- and medium-scale coseismic landslides can be used to effectively determine the source parameters of historical strong earthquakes and perform quantitative evaluations. This study evaluates the focal parameters of the 780 BC Qishan earthquake based on interpretations of the spatial distribution range of historical landslides as representations of the range of the extreme earthquake zone.