Pulse-type ground motion discrimination and classification method based on multi-dimension synthesis

Abstract

A multi-dimensional comprehensive method for identifying and classifying the causes of pulse-type ground motions, belonging to the fields of earthquake engineering and engineering seismology, is proposed. This method involves determining the pulse type and filtering the validity of input ground motion records; obtaining the fault distance between the station and the seismogenic fault and performing initial near-field / far-field subdivision; identifying surface wave amplification and energy capture effects by combining site environment data; and identifying forward directional effects by combining the fault rupture propagation direction and the station's relative position. Based on the above identification results, pulse-type ground motions are classified into three types by comprehensively judging macroscopic characteristics such as pulse amplitude, principal period, duration, and waveform continuity in the velocity time history: ground motions dominated by forward directional effects, ground motions dominated by surface wave effects, and composite ground motions formed by the combined effects of surface wave effects and forward directional effects. This invention enables a precise classification of pulse-type ground motions from a physical cause perspective.

Description

Technical Field

[0001] This invention belongs to the field of earthquake engineering and engineering seismology, and specifically relates to a method for quantitatively classifying pulse-type ground motions caused by different geological effects (including forward directional effects, basin surface wave effects and their coupling effects) based on pulse-type ground motion determination, taking into account the geographical location of the station, geological structural conditions and macroscopic characteristics of velocity time history. Background Technology

[0002] In earthquake engineering practice, earthquake motions generated by different geological conditions and seismic source rupture characteristics exhibit significant differences in amplitude characteristics, spectral distribution, and duration, resulting in varying failure mechanisms for engineering structures. Particularly in near-fault regions, the forward directional effect generated during fault rupture often leads to large-amplitude velocity pulses in earthquake motions, rich in medium- and long-period components, posing a serious threat to medium- and high-rise structures and long-period structures.

[0003] Meanwhile, in plains or sedimentary basins far from faults, the high-frequency body wave components of seismic waves gradually attenuate during propagation, while the low-frequency components are preserved. When low-frequency seismic waves enter deep, weak sedimentary layers, they are easily affected by dispersion, amplification, and energy trapping effects, thereby exciting long-period ground motions dominated by surface waves. These ground motions are typically characterized by long duration, relatively flat waveforms, but large accumulated energy.

[0004] In practical engineering, some stations record long-period pulse-type ground motions simultaneously located in fault-prone areas and sedimentary basin environments. Their waveform characteristics often exhibit both distinct velocity pulses and multi-period continuous oscillations, reflecting the coupling effect of forward directional effects and basin surface wave effects. Existing methods primarily focus on classifying ground motions into near-field or far-field categories based on fault distance, making it difficult to further distinguish between the aforementioned pulse-type ground motion types with different physical origins. This restricts the rational selection of ground motion inputs in seismic design. Therefore, it is necessary to propose a pulse-type ground motion classification method that comprehensively considers geographical location, geological conditions, and pulse waveform characteristics. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides a method for identifying and classifying pulse-type ground motions based on multi-dimensional comprehensive analysis. Building upon existing pulse-type ground motion determination results, this method further subdivides pulse-type ground motions from the perspective of physical causes, providing a more refined and reliable basis for ground motion classification in engineering seismic design.

[0006] The technical solution adopted by this invention to solve its technical problem is: A method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional integration includes the following steps: Step S1, Pulse-type ground motion determination: Perform pulse-type ground motion determination on the input ground motion records and filter out ground motion records with significant pulse characteristics; Step S2, Validity Screening of Pulse-Type Ground Motion Records: For ground motion records identified as pulse-type in Step S1, abnormal records that do not have engineering analysis significance are removed based on record completeness, effective duration, and overall velocity time history, in order to ensure the stability and reliability of subsequent classification results. Step S3: Spatial location discrimination based on fault distance: Obtain the fault distance information of the observation station relative to the seismogenic fault, and make a preliminary distinction between the near field and far field of the pulse-type ground motion based on whether the fault distance is less than a preset threshold. Step S4: Environmental identification based on site geological conditions: Combine the geological conditions of the area where the observation station is located to determine whether the station is located in a plain, sedimentary basin or other soft site environment, and identify possible surface wave amplification and capture effects accordingly. Step S5: Directional relationship analysis based on fault rupture propagation direction: Combine the rupture propagation direction of the seismic fault with the spatial relative position of the observation station to determine whether the station is located in the area in front of the fault rupture propagation, so as to identify the influence of forward directional effect on velocity pulse formation. Step S6: Causal classification based on macroscopic characteristics of velocity pulses: Based on the discrimination results of steps S3 to S5, the macroscopic waveform characteristics of the pulses in the velocity time history are comprehensively analyzed to classify the causes of pulse-type ground motions.

[0007] Furthermore, in step S2, record integrity means that there are no missing values ​​or abnormal spikes in the record, and the average velocity within the first 2 seconds and the last 1 second does not exceed 1% of the peak velocity; effective duration means that the time difference corresponding to the accumulation of Arias intensity from 5% to 95% is not less than 2.0 seconds; overall velocity time history shape means that the ratio of peak velocity to the average absolute velocity over the entire time history is ≥5.0, and the residual of displacement obtained by integrating the velocity time history at the end of the record is not greater than 10% of the absolute value of the maximum displacement.

[0008] Furthermore, in step S3, the fault distance can be directly obtained from station information in the NGA-West2 database provided by PEER (Pacific Earthquake Engineering Research Center), or calculated based on parameters such as fault strike, dip angle, and rupture length. The selected fault distance ( R jb A near-field threshold of less than 30 km is used to initially distinguish ground motion records that may be affected by forward directional effects.

[0009] Furthermore, in step S4, the average shear wave velocity at a depth of 30 meters below the ground surface of the station is used as the basis for further steps. VS30 As a core discriminant indicator: V S30 Sites with a speed <180m / s are classified as soft soil sites; sites with a speed ≤180m / s are classified as soft soil sites. V S30 A velocity of <360m / s indicates a typical sedimentation site. V S30 A surface wave velocity ≥360 m / s indicates a non-soft site. This is further considered in conjunction with whether the station is located within an alluvial plain or sedimentary basin. If the site meets the criteria of soft soil or a typical sedimentary site located in a flat sedimentary area, then a surface wave amplification effect is likely present. V S30 Data was obtained from the PEER NGA-West2 database or related literature.

[0010] In step S5, the following quantitative indicators are used for judgment: (1) Spatial geometric conditions: calculate the azimuth difference of the station relative to the fault rupture propagation direction. θ ,like θ If the angle is ≤30° and the station is located in front of the rupture, it is initially determined to be a forward region; (2) Verification of ground motion characteristics: The ground motion of this station simultaneously satisfies: ① long period, that is T ≥1.0s response spectrum magnification factor ≥1.2; ② Significant duration ratio with stations at the same distance behind the rupture ≤0.6; If all of the above conditions are met, the station is determined to be affected by the forward directional effect.

[0011] In step S6, category one, namely, the seismic motion dominated by forward directional effects, satisfies: Spatial discrimination: fault distance R jb ≤ 30 km and located in the area ahead of the rupture; Waveform characteristics: A large, isolated, and complete long-period pulse with strong bursts, where energy release is highly concentrated within a single pulse period; Category 2, namely, seismic motions dominated by surface wave effects, satisfy the following: Spatial discrimination: R jb > 30 km and located in soft terrain; Waveform characteristics: It does not appear as an isolated single pulse, but rather as an oscillating pattern with multiple peaks and troughs alternating continuously within a time period containing three or more significant velocity half-waves; Category 3, namely, the combined seismic motion formed by the combined effects of surface wave effect and forward directional effect, satisfies: Spatial discrimination: 0 km ≤ R jb ≤ 80 km and located in a deep sedimentary plain environment; Waveform characteristics: Within a continuous interval containing two or more significant velocity half-waves, multiple long-period velocity pulses with significant amplitudes and similar periods appear consecutively.

[0012] The causes of pulse-type ground motions in this invention are classified as follows: 6.1. Ground motions dominated by forward directional effects: Their physical origin stems from the Doppler effect generated by the propagation of fault rupture towards the observation station. Spatially, these ground motions are significantly concentrated in the near-field region, exhibiting a high fault distance (…). R jb The wavelength is less than 30 km; its waveform characteristics are characterized by isolated and complete long-period pulses with strong suddenness, and the energy release is highly concentrated within a single pulse period, resulting in a short duration of its main energy segment. 6.2. Ground motions dominated by surface wave effects: Their physical origin stems from the dispersion and energy capture effects generated after seismic waves enter deep, weak sedimentary layers or basin environments. Spatially, these ground motions are usually located in far-field regions far from faults, with fault distances greater than 30 km, and are mostly located within alluvial plains or sedimentary basins. Their waveform characteristics do not manifest as isolated single pulses, but rather as an oscillation pattern of multiple wave peaks and troughs alternating continuously over a long period of time. Due to the significant attenuation of high-frequency body wave components and the slow release of low-frequency energy with surface waves, the ground motions have a significant long duration. 6.3 Composite ground motions formed by the combined effects of surface wave effect and forward directional effect: The physical cause is the superposition and coupling of the direct impact of fault rupture and the special geological influence of sedimentary layers. Spatially, these ground motions are mostly located in the mid-to-near field region (fault distance range of 0-80 km), and the observation stations are located in deep sedimentary plain environments. Their waveform characteristics are characterized by the continuous appearance of multiple long-period velocity pulses with significant amplitude and similar period over a long time interval. This category combines the high amplitude characteristics of directional effect with the long duration characteristics of surface wave effect, resulting in extremely high seismic energy concentration and the strongest destructive force on engineering structures.

[0013] The technical concept of this invention is as follows: Based on the completed determination of pulse-type ground motions, this invention comprehensively incorporates the spatial location of observation stations, fault distance, site geological conditions, and macroscopic waveform characteristics of velocity pulses to classify pulse-type ground motions. The method includes: determining the pulse type of input ground motion records and screening for validity; obtaining the fault distance of the station relative to the seismogenic fault and completing the near-field / far-field initial division; identifying surface wave amplification and energy capture effects in conjunction with the site environment, and identifying forward directional effects in conjunction with the fault rupture propagation direction and the relative position of the station; based on the above discrimination results, by comprehensively judging the macroscopic characteristics such as the amplitude, principal period, duration, and waveform continuity of the pulse in the velocity time history, pulse-type ground motions are classified into: ground motions dominated by forward directional effects, ground motions dominated by surface wave effects, and composite ground motions formed by the combined effects of surface wave effects and forward directional effects. This invention can provide a fine classification of pulse-type ground motions from a physical origin perspective, providing a more scientific and reliable basis for regional seismic design and the selection of long-period structural ground motions.

[0014] The beneficial effects of this invention are mainly reflected in: 1. A more refined and scientific classification system: This invention breaks through the limitations of the traditional method of roughly dividing near-field and far-field motions based solely on fault distance, further subdividing long-period earthquakes that pose a significant threat to structures into three categories: "dominated by forward directional effects," "caused by surface waves," and "caused by the interaction of surface waves and forward directional effects." This subdivision can more accurately reveal the physical causes of earthquakes and their different mechanisms of structural damage. 2. Providing precise basis for seismic design: By identifying the coupling effect between forward directionality and surface waves, this invention can screen out composite ground motions with extremely high energy concentration and strong destructive force. This provides design inputs that are more consistent with the actual seismic damage characteristics for urban areas located in sedimentary basins and close to faults (such as areas with dense mid-to-high-rise buildings), helping to improve the safety and economy of seismic design. Attached Figure Description

[0015] Figure 1 This is a velocity time history diagram of the ground motion at station TCU068 as described in Embodiment 1 of the present invention; Figure 2 This is a velocity time history diagram of the ground motion at station TCU033 as described in Embodiment 1 of the present invention; Figure 3 This is a velocity time history diagram of the ground motion at the CHY002 station described in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0016] The present invention will now be further described with reference to the accompanying drawings.

[0017] Reference Figures 1-4 A method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional comprehensive analysis includes the following steps: Step S1, Pulse-type ground motion determination: The input ground motion records are subjected to pulse-type ground motion determination to filter out ground motion records with significant pulse characteristics; the pulse-type ground motion determination can be implemented using existing pulse recognition methods, and the present invention does not limit the specific determination algorithm.

[0018] In this embodiment, the pulse-type ground motion identification method based on significant velocity half-wave proposed by Zhai et al. (2018) is used. Of course, other equivalent pulse identification algorithms can also be used, such as the wavelet analysis-based identification method proposed by Baker (2007), the fitting method based on velocity pulse model, or the identification method based on energy ratio threshold, etc., and this invention does not strictly limit them.

[0019] Step S2, Validity Screening of Pulse-Type Ground Motion Records: For ground motion records identified as pulse-type in Step S1, abnormal records that do not have engineering analysis significance are removed based on record completeness, effective duration, and overall velocity time history, in order to ensure the stability and reliability of subsequent classification results. In this embodiment, record integrity means that there are no missing values ​​or abnormal spikes in the record, and the average velocity within the first 2 seconds and the last 1 second does not exceed 1% of the peak velocity; effective duration means that the time difference corresponding to the accumulation of Arias intensity from 5% to 95% is not less than 2.0 seconds; the overall shape of velocity time history means that the ratio of peak velocity to the average absolute velocity of the whole time history is ≥5.0, and the residual of displacement obtained by integrating the velocity time history at the end of the record is not greater than 10% of the absolute value of the maximum displacement.

[0020] Step S3: Spatial location discrimination based on fault distance: Obtain the fault distance information of the observation station relative to the seismogenic fault, and make a preliminary distinction between the near field and far field of the pulse-type ground motion based on whether the fault distance is less than a preset threshold. In this embodiment, the fault distance can be directly obtained from the station information in the NGA-West2 database provided by PEER (Pacific Earthquake Engineering Research Center), or calculated based on parameters such as fault strike, dip angle and rupture length. A fault distance of less than 30 km is selected as the near-field discrimination threshold to preliminarily distinguish ground motion records that may be affected by forward directional effects.

[0021] Step S4: Environmental identification based on site geological conditions: Combine the geological conditions of the area where the observation station is located to determine whether the station is located in a plain, sedimentary basin or other soft site environment, and identify possible surface wave amplification and capture effects accordingly. In this embodiment, the average shear wave velocity at 30 meters below the ground surface of the station (V S30 As the core discriminant indicator: V S30 Sites with a speed <180m / s are classified as soft soil sites; sites with a speed ≤180m / s are classified as soft soil sites. V S30 A velocity of <360m / s indicates a typical sedimentation site. V S30 A surface wave velocity of ≥360 m / s indicates a non-weak site. Additionally, the location of the station should be considered in conjunction with whether it is situated within an alluvial plain or sedimentary basin. If the site meets the criteria of weak soil or a typical sedimentary site located in a flat sedimentary area, then a surface wave amplification effect is likely present. V S30 Data can be obtained from the PEER NGA-West2 database or related literature.

[0022] Step S5: Directional relationship analysis based on fault rupture propagation direction: Combine the rupture propagation direction of the seismic fault with the spatial relative position of the observation station to determine whether the station is located in the area in front of the fault rupture propagation, so as to identify the influence of forward directional effect on velocity pulse formation. In this embodiment, the following quantitative indicators are used for determination: (1) Spatial geometric conditions: Calculate the azimuth difference of the station relative to the direction of fault rupture propagation. θ ,like θ If the angle is ≤30° and the station is located in front of the rupture, it is initially determined to be a forward-looking region.

[0023] (2) Verification of ground motion characteristics: The ground motion at this station simultaneously satisfies: ① Long period ( T ≥1.0s) Magnification factor of the reaction spectrum ≥1.2; ② The ratio of significant duration to that of stations at the same distance behind the rupture ≤0.6.

[0024] If all of the above conditions are met, the station is determined to be affected by the forward directional effect.

[0025] Step S6: Causal Classification Based on Macroscopic Characteristics of Velocity Pulses: Based on the discrimination results of steps S3 to S5, the macroscopic waveform characteristics of the pulses in the velocity time history are comprehensively analyzed to classify the causes of pulse-type ground motions as follows: 6.1 Category 1, namely, ground motions dominated by forward directional effects: Their physical origin stems from the Doppler effect generated by the propagation of fault rupture towards the observation station. Spatially, this type of ground motion is significantly concentrated in the near-field region, manifested as a fault distance (…). R jb The waveform characteristics are characterized by isolated and complete long-period pulses with strong suddenness, and the energy release is highly concentrated within a single pulse period, resulting in a short duration of its main energy segment. 6.2 Classification 2, namely, ground motion dominated by surface wave effect: its physical cause is the dispersion and energy capture effect generated after seismic waves enter a deep and weak sedimentary layer or basin environment. Spatially, this type of ground motion is usually located in the far field region far from the fault, with a fault distance greater than 30 km, and is mostly located in alluvial plains or sedimentary basins. Its waveform characteristics do not show isolated single pulses, but rather exhibit an oscillation pattern of multiple wave peaks and troughs that alternate continuously over a long period of time. Due to the significant attenuation of high-frequency body wave components and the slow release of low-frequency energy with surface waves, the ground motion has a significant long duration. 6.3 Category 3, namely, composite ground motions formed by the combined effects of surface wave effect and forward directional effect: its physical cause is the superposition and coupling of the direct impact of fault rupture and the special geological influence of sedimentary layers. In terms of spatial distribution, such ground motions are mostly located in the mid-to-near field region (fault distance range of 0-80 km), and the observation stations are located in the environment of deep sedimentary plains. Its waveform characteristics are characterized by the continuous appearance of multiple long-period velocity pulses with significant amplitude and similar period over a long time interval. This category combines the high amplitude characteristics of directional effect with the long duration characteristics of surface wave effect, resulting in extremely high seismic energy concentration and the strongest destructive force on engineering structures.

[0026] In this embodiment, category one, namely the seismic motion dominated by forward directional effects, satisfies: Spatial discrimination: R jb ≤ 30 km and located in the area ahead of the rupture; Waveform characteristics: It is an isolated and complete long-period pulse with strong suddenness, and the energy release is highly concentrated within a single pulse period.

[0027] Category 2, namely, seismic motions dominated by surface wave effects, satisfy the following: Spatial discrimination: R jb > 30 km and located in soft terrain; Waveform characteristics: It does not appear as an isolated single pulse, but rather as an oscillating pattern with multiple peaks and troughs alternating continuously within a time period containing three or more significant velocity half-waves.

[0028] Category 3, namely, the combined seismic motion formed by the combined effects of surface wave effect and forward directional effect, satisfies: Spatial discrimination: 0 km ≤ R jb ≤ 80 km and located in a deep sedimentary plain environment; Waveform characteristics: Within a continuous interval containing two or more significant velocity half-waves, multiple long-period velocity pulses with significant amplitudes and similar periods appear consecutively.

[0029] The following three specific examples from seismic stations illustrate the process of classifying three different types of ground motions according to this invention: Example 1: Earthquake motion dominated by forward directional effects (Classification 1), using data from station TCU068 during the 1999 Chi-Chi earthquake in Taiwan. The implementation process is as follows: Step 1: Geographical Location Analysis: This station is located ahead of the propagation of the Chelongpu Fault rupture and is extremely close to the fault (Rjb = 0.01 km), belonging to the near-field region. The fault rupture front moves towards the station at a velocity close to that of a shear wave, producing a significant forward directional effect; Step 2, Pulse Identification and Characteristics: The significant velocity half-wave method of this invention is applied to analyze its velocity time history (e.g., Figure 1 (As shown). Within the time interval of 33 to 44 seconds, the waveform burst forms a complete long-cycle pulse containing a large positive peak and a negative trough. The instantaneous peak velocity of this pulse reaches 264.09 cm / s, and the duration of this single pulse cycle occupies the main energy release period. Step 3: The judgment result is Class I, namely, pulse-type ground motion dominated by forward directional effect.

[0030] Example 2: Earthquake motion caused by surface waves (Category II), using data from station TCU033 during the 1999 Chi-Chi earthquake in Taiwan. The implementation process is as follows: Step 1, Geographical Location Analysis: This station is located on the alluvial plain of northwestern Taiwan, in a deep soft soil sedimentary environment. Although it is located in front of the fault rupture, its geometric distance from the epicenter and the fault is significantly far, Rjb = 40.88 km, placing it in the far field region; Step 2, Pulse Identification and Characteristics: Analyze its velocity time history (e.g., Figure 2 As shown, the waveform does not appear as an isolated large pulse, but rather exhibits an alternating oscillation pattern of multiple peaks and troughs over a long period of 40 to 80 seconds. High-frequency body waves are attenuated, while low-frequency surface waves are amplified due to the dispersion and trapping effect of the soft soil layer in the basin. Step 3: The result is classified as Category II, namely, pulse-type ground motion caused by surface waves.

[0031] Example 3: Earthquake motion caused by the interaction of surface waves and forward directional effects (Classification 3), using the CHY002 station record from the 1999 Chi-Chi earthquake in Taiwan. The implementation process is as follows: Step 1: Geographical Location Analysis: This station is located ahead of the propagation of the Chelungpu Fault and is relatively close to the fault (Rjb=24.96km), while also situated in a deep sedimentary plain area along the western coast of Taiwan. This unique location means it is subjected to both the direct impact of the fault rupture and the geological influence of the sedimentary layers. Step 2, Pulse Identification and Characteristics: Analyze its velocity time history (e.g., Figure 3 As shown in the figure, within the range of 45 to 65 seconds, multiple long-period velocity pulses with significant amplitude and similar period are observed, with a peak velocity of 56.16 cm / s. This is different from the near-field single pulse characteristics and also different from the far-field stable long-duration oscillation characteristics, reflecting the superposition and coupling effect of forward directional effect and surface wave effect. Step 3: The judgment result is Class III, namely, pulse-type ground motion caused by the interaction of surface waves and forward directional effects.

[0032] The embodiments described in this specification are merely examples of implementations of the inventive concept and are for illustrative purposes only. The scope of protection of this invention should not be considered limited to the specific forms described in these embodiments; rather, it extends to equivalent technical means conceived by those skilled in the art based on the inventive concept.

Claims

1. A method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional comprehensive analysis, characterized in that, The method includes the following steps: Step S1, Pulse-type ground motion determination: Perform pulse-type ground motion determination on the input ground motion records and filter out ground motion records with significant pulse characteristics; Step S2, Validity Screening of Pulse-Type Ground Motion Records: For ground motion records identified as pulse-type in Step S1, abnormal records that do not have engineering analysis significance are removed based on record completeness, effective duration, and overall velocity time history, in order to ensure the stability and reliability of subsequent classification results. Step S3: Spatial location discrimination based on fault distance: Obtain the fault distance information of the observation station relative to the seismogenic fault, and make a preliminary distinction between the near field and far field of the pulse-type ground motion based on whether the fault distance is less than a preset threshold. Step S4: Environmental identification based on site geological conditions: Combine the geological conditions of the area where the observation station is located to determine whether the station is located in a plain, sedimentary basin or other soft site environment, and identify possible surface wave amplification and capture effects accordingly. Step S5: Directional relationship analysis based on fault rupture propagation direction: Combine the rupture propagation direction of the seismic fault with the spatial relative position of the observation station to determine whether the station is located in the area in front of the fault rupture propagation, so as to identify the influence of forward directional effect on velocity pulse formation. Step S6: Causal classification based on macroscopic characteristics of velocity pulses: Based on the discrimination results of steps S3 to S5, the macroscopic waveform characteristics of the pulses in the velocity time history are comprehensively analyzed to classify the causes of pulse-type ground motions.

2. The method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional comprehensive analysis as described in claim 1, characterized in that: In step S2, record integrity means that there are no missing values ​​or abnormal spikes in the record, and the average velocity within the first 2 seconds and the last 1 second does not exceed 1% of the peak velocity; effective duration means that the time difference corresponding to the accumulation of Arias intensity from 5% to 95% is not less than 2.0 seconds; overall velocity time history shape means that the ratio of peak velocity to the average absolute velocity of the whole time history is ≥5.0, and the residual of displacement obtained by integrating the velocity time history at the end of the record is not greater than 10% of the absolute value of the maximum displacement.

3. The method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional comprehensive analysis as described in claim 1, characterized in that, In step S3, the fault distance is obtained directly from the station information in the NGA-West2 database provided by PEER, or calculated based on the fault strike, dip angle and rupture length parameters. A fault distance of less than 30 km is selected as the near-field discrimination threshold to preliminarily distinguish ground motion records that may be affected by forward directional effects.

4. The method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional comprehensive analysis as described in claim 1, characterized in that, In step S4, the average shear wave velocity at 30 meters below the ground surface of the station is used. V S30 As a core discriminant indicator: V S30 Sites with a speed <180m / s are classified as soft soil sites; sites with a speed ≤180m / s are classified as soft soil sites. V S30 A velocity of <360m / s indicates a typical sedimentation site. V S30 ≥360m / s indicates a non-weak site. In addition, it is necessary to consider whether the station is located in an alluvial plain or sedimentary basin. If it meets the criteria of weak soil or general sedimentary site and is located in a flat sedimentary area, then it is determined that there may be a surface wave amplification effect.

5. The method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional comprehensive analysis as described in claim 1, characterized in that, In step S5, the following quantitative indicators are used for judgment: (1) Spatial geometric conditions: calculate the azimuth difference of the station relative to the direction of fault rupture propagation. θ ,like θ If the angle is ≤30° and the station is located in front of the rupture, it is initially determined to be a forward region; (2) Verification of ground motion characteristics: The ground motion of this station simultaneously satisfies: ① long period, that is T ① ≥1.0s response spectrum magnification factor ≥1.2; ② Significant duration ratio with stations at the same distance behind the rupture ≤0.6; If all of the above conditions are met, the station is determined to be affected by the forward directional effect.

6. The method for identifying and classifying the causes of pulse-type ground motions based on multi-dimensional comprehensive analysis as described in claim 1, characterized in that, In step S6, category one, namely, the seismic motion dominated by forward directional effects, satisfies: Spatial discrimination: fault distance R jb ≤ 30 km and located in the area ahead of the rupture; Waveform characteristics: A large, isolated, and complete long-period pulse with strong bursts, where energy release is highly concentrated within a single pulse period; Category 2, namely, seismic motions dominated by surface wave effects, satisfy the following: Spatial discrimination: R jb > 30 km and located in soft terrain; Waveform characteristics: It does not appear as an isolated single pulse, but rather as an oscillating pattern with multiple peaks and troughs alternating continuously within a time period containing three or more significant velocity half-waves; Category 3, namely, the combined seismic motion formed by the combined effects of surface wave effect and forward directional effect, satisfies: Spatial discrimination: 0 km ≤ R jb ≤ 80 km and located in a deep sedimentary plain environment; Waveform characteristics: Within a continuous interval containing two or more significant velocity half-waves, multiple long-period velocity pulses with significant amplitudes and similar periods appear consecutively.

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