This study focuses on two aftershocks of magnitude 5.0 or above in the Haicheng earthquake of 1975, and explores in depth the directional characteristics of their ground motion and the relationship with the seismogenic fault. The response directional characteristics of several types of structures were analyzed using structural measurement point records. First, the background of the Haicheng earthquake is explained, subsequently based on analysis methods such as omnidirectional response spectrum, duration spectrum, and input energy spectrum, the vibration records of six observation stations in Haicheng and Yingkou were analyzed in detail. The results show that the variation of ground motion intensity in different directions is significant, especially when the period is between 1.5~3.5 seconds. The directional effect of seismic intensity of Haicheng aftershocks is more significant than that of the SB14 model of NGA-West2. The directional effect of long-period (≥1.0 s) is particularly prominent, and in the long-period frequency band, the directional difference of near fault ground motion is more pronounced. In the high-frequency range of the omnidirectional response spectrum, there is a high correlation between the east-west dominant direction and the F2 east-west hidden fault, while the mid low frequency range clearly shows the directional characteristics of the F1 north northwest main fault. The directionality of structural reactions may undergo some changes due to structural factors, such as structural form, major and minor axes, site conditions, etc. The seismic response directionality of bridge piers is basically consistent with the free field directionality, while there is a certain degree of rotation in the directional response of building structures.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |