SUMMARY The crustal attenuation structure can effectively reveal the rheology and thermal properties of different geological blocks, and can provide seismological constraints on regional tectonic evolution. Based on 11 306 vertical-component Lg-wave seismograms recorded at 111 broad-band stations from 891 crustal earthquakes that occurred between 1994 and 2020, a broad-band Lg-wave attenuation model is obtained for Southeast Asia. This study demonstrates the capability of applying crustal Lg-wave attenuation inversion in a complex region mixed with continents, islands and marginal seas. The resolution approaches 2° in most parts in the study region. Lg blockages are observed at places with sharp Moho depth changes. The resultant Q models are consistent with regional geologic structures provided by previous studies. Prominent low-attenuation anomalies are located in the Sundaland Core containing stable ancient crust, including Indochina, Malay Peninsula, East Sumatra, Sunda Shelf and Borneo Core. Regions with strong attenuation are associated with complex tectonic conditions, such as the Indo–Australian subduction zone, sutures in Sarawak and Sabah. The observed Lg-wave attenuation characteristics provide constraints on the tectonic affinities and evolutions of the geological blocks. The results show that the Borneo Core remained stable since its accretion with the Sundaland Core. Ancient blocks are characterized by weak Lg attenuation, whereas geologically younger terranes are often characterized by strong Lg attenuation, which can be exploited to better understand the separation and convergence of plates during the tectonic evolution.

中文翻译：

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东南亚地壳 Lg 波衰减及其对区域构造演化的意义

总结 地壳衰减结构能够有效揭示不同地质块体的流变学和热学性质，为区域构造演化提供地震学约束。基于1994-2020年间发生的891次地壳地震的111个宽带台站记录的11 306个垂直分量Lg波地震图，获得了东南亚的宽带Lg波衰减模型。这项研究证明了在混合大陆、岛屿和边缘海的复杂区域应用地壳 Lg 波衰减反演的能力。研究区大部分地区的分辨率接近 2°。在莫霍面深度变化剧烈的地方观察到 Lg 阻塞。由此产生的 Q 模型与先前研究提供的区域地质结构一致。突出的低衰减异常位于含有稳定古地壳的巽他地核，包括印度支那、马来半岛、东苏门答腊、巽他陆架和婆罗洲核。衰减强烈的区域与复杂的构造条件有关，例如印澳俯冲带、砂拉越和沙巴的缝合线。观测到的 Lg 波衰减特征为地质块的构造亲和力和演化提供了约束。结果表明，婆罗洲核心自与巽他地核心吸积以来保持稳定。古块体具有弱 Lg 衰减的特征，而地质上较年轻的地体通常具有强 Lg 衰减的特征，可用于更好地了解构造演化过程中板块的分离和汇聚。