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澳大利亚大陆的地震速度结构多以面波层析成像、地震折射、接收函数和噪声层析成像为主。澳大利亚大陆的三维速度结构已被总结成澳大利亚地震参考模型(AuSREM)。Pn波走时层析成像可提供整个该大陆更强约束的上地幔结构信息。本文调查了自1993年以来发生在澳大利亚大陆内部大的地震事件的波形和地震震相报告,这些地震事件被固定台站和流动台站所记录。为克服澳大利亚东西部大的横向速度对比和保证震源参数的一致性,所有的地震事件在三维澳大利亚参考速度模型中进行了地震重定位。地震重定位后发现,地震震相的走时残差特征具有良好的一致性。定义Pn波为震中距1.8~15°范围内的初至波。利用FMTOMO方法反演走时差以获得上地幔顶部的P波速度结构,其分辨率为3°×3°。反演结果表明,整个澳大利亚大陆上地幔顶部P波速度呈强烈的横向不均匀性。P波的最大速度为8.36km/s,位于澳大利亚西部和中部的前寒武纪克拉通下方,其比全球ak135模型的P波速度快3.99%;最慢的P波速度为7.66km/s,其位于澳大利亚大陆东缘显生宙造山带之下,较全球ak135模型慢4.74%,这可能与晚第三纪火山活动有关。
Most of the seismic velocity structures in the mainland of Australia are surface wave tomography, seismic refraction, receiver function and noise tomography. The three-dimensional velocity structure of the Australian continent has been summarized in the Australian Seismic Reference Model (AuSREM). Pn wave travel tomography provides more constrained upper mantle structure information throughout the continent. This paper investigates waveform and seismic phase reports of major earthquakes that occurred in mainland Australia since 1993 and was recorded by both stationary and mobile stations. To overcome the large horizontal velocity contrast between eastern and western Australia and to ensure coherence of source parameters, all seismic events were repositioned in a three-dimensional Australian reference velocity model. After the earthquake was relocated, it was found that the characteristics of the traveltime residuals of the seismic phases are in good agreement. The Pn wave is defined as the first arrival wave in the range of 1.8 ~ 15 °. The FMTOMO method is used to retrieve the travel time difference to obtain the P wave velocity structure at the top of the upper mantle with a resolution of 3 ° × 3 °. The inversion results show that there is a strong lateral heterogeneity of P-wave velocity at the top of the mantle over the entire Australian continent. The maximum P wave velocity is 8.36 km / s, located below the Precambrian craton in the western and central Australia, which is 3.99% faster than the global ak135 model. The slowest P wave velocity is 7.66 km / s, It is located below the Phanerozoic orogenic belt on the eastern margin of the Australian mainland, 4.74% slower than the global ak135 model, which may be related to late-Tertiary volcanic activity.