Abstract Stacking over 2300 P-to-S receiver functions recorded by 33 SAFARI (Seismic Arrays for African Rift Initiation) broadband seismic stations that we installed in the vicinity of the Malawi and Luangwa rift zones (MRZ and LRZ, respectively) reveals significant variations of crustal thickness (32.8–46.3 km) and Vp/Vs (1.69–1.85). The resulting crustal stretching factor is about 1.05–1.08 for the MRZ, which is approximately 10–40% lower than that observed in the mature segments of the East African Rift System (EARS). The low stretching factor is consistent with the general absence of volcanism in the MRZ, and the relatively high Vp/Vs (≥ 1.81) beneath the southern MRZ, when combined with observations from previous studies, indicate the possible existence of crustal partial melting, elevated temperatures or fluid-filled deep crustal faults that are likely associated with lithospheric stretching. In sharp contrast with the southern MRZ, low Vp/Vs measurements in the range of 1.69–1.72 are observed along the western boundary of the northern MRZ, which could be attributable to the infiltration of magma-derived CO2 into the crust. The LRZ shows negligible crustal thinning and a Vp/Vs that is comparable to the globally averaged value for continental crust, suggesting a complete post-rifting recovery of crustal properties in terms of crustal thickness and VpVs.

中文翻译：

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马拉维和卢安瓜裂谷带及邻区地壳结构接收函数研究

摘要 将我们安装在马拉维和卢安瓜裂谷带（分别为 MRZ 和 LRZ）附近的 33 个 SAFARI（非洲裂谷起始地震阵列）宽带地震台记录的 2300 多个 P-to-S 接收器函数叠加在一起，揭示了地壳厚度 (32.8–46.3 km) 和 Vp/Vs (1.69–1.85)。由此产生的地壳拉​​伸因子对于 MRZ 约为 1.05-1.08，比在东非裂谷系统 (EARS) 成熟段观察到的要低 10-40%。低拉伸因子与 MRZ 中普遍不存在火山活动相一致，而 MRZ 南部下方相对较高的 Vp/Vs（≥1.81），结合先前研究的观察结果，表明可能存在地壳部分熔融，可能与岩石圈拉伸有关的高温或充满流体的深部地壳断层。与南部 MRZ 形成鲜明对比的是，沿北部 MRZ 的西部边界观察到 1.69-1.72 范围内的低 Vp/Vs 测量值，这可能归因于岩浆衍生的 CO2 渗入地壳。LRZ 显示出可忽略不计的地壳减薄和与大陆地壳全球平均值相当的 Vp/Vs，表明在地壳厚度和 VpVs 方面地壳性质在裂谷后完全恢复。这可能归因于岩浆衍生的 CO2 渗入地壳。LRZ 显示出可忽略不计的地壳减薄和与大陆地壳全球平均值相当的 Vp/Vs，表明在地壳厚度和 VpVs 方面地壳性质在裂谷后完全恢复。这可能归因于岩浆衍生的 CO2 渗入地壳。LRZ 显示出可忽略不计的地壳减薄和与大陆地壳全球平均值相当的 Vp/Vs，表明在地壳厚度和 VpVs 方面地壳性质在裂谷后完全恢复。