We use a large data set of 3D thermal evolution models to predict the distribution of present-day seismic velocities in the Martian interior. Our models show a difference between maximum and minimum S wave velocity of up to 10% either below the crust, where thermal variations are largest, or at the depth of the olivine to wadsleyite phase transition, located at around 1,000–1,200 km depth. Models with thick lithospheres on average have weak low-velocity zones that extend deeper than 400 km and seismic velocity variations in the uppermost 400–600 km that closely follow the crustal thickness pattern. For these cases, the crust contains more than half of the total amount of heat-producing elements. Models with limited crustal heat production have thinner lithospheres and shallower but prominent low-velocity zones that are incompatible with Interior exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) observations. Seismic events suggested to originate in Cerberus Fossae indicate the absence of S wave shadow zones in 25°–30° epicentral distance. This result is compatible with previous best fit models that require a large average lithospheric thickness and a crust containing more than half of the bulk amount of heat-producing elements to be compatible with geological and geophysical constraints. Ongoing and future InSight measurements that will determine the existence of a weak low-velocity zone will directly bear on the crustal heat production.

中文翻译：

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3D 火星地幔中的地震速度变化：对洞察力测量的影响

我们使用大量 3D 热演化模型数据集来预测火星内部当今地震速度的分布。我们的模型显示最大和最小S之间的差异地壳下方热变化最大的地方，或者在橄榄石到瓦兹利岩相变的深度，位于大约 1,000-1,200 公里的深度，波速高达 10%。岩石圈较厚的模型平均有延伸超过 400 公里的弱低速带，最上面 400-600 公里的地震速度变化与地壳厚度模式密切相关。在这些情况下，地壳含有超过一半的发热元素。地壳产热有限的模型具有更薄的岩石圈和更浅但突出的低速带，这与使用地震调查、大地测量和热传输 (InSight) 观测的内部勘探不相容。建议起源于 Cerberus Fossae 的地震事件表明没有S25°–30° 震中距内的波影带。这一结果与之前的最佳拟合模型兼容，这些模型需要较大的平均岩石圈厚度和包含超过一半的发热元素的地壳，才能与地质和地球物理约束兼容。正在进行和未来的 InSight 测量将确定弱低速带的存在，这将直接影响地壳热量的产生。