Volcanic explosions can produce large, ash-rich plumes that pose great hazard to aviation, yet may often have few precursory geophysical signals. Mount Cleveland is one of the most active volcanoes in the Aleutian Arc, Alaska (United States) with at least 65 explosions between December 2011 and June 2020. We characterize the seismo-acoustic signals from explosions at Mount Cleveland over a period of 4 years starting in 2014 when the permanent local instrumentation was installed. While the seismic explosion signals are similar, the acoustic signals vary between explosions. Some explosion acoustic waveforms exhibit a single main compressional phase while other waveforms have multiple compressions. The time lag between seismic and acoustic arrivals varies considerably (up to 2.20 s) at a single station ∼3 km from the vent, suggesting a change in propagation path for the signals between explosions. We apply a variety of methods to explore the potential contributions to this variable time lag from atmospheric conditions, nonlinear propagation, and source depth within the conduit. This variable time lag has been observed elsewhere, but explanations are often unresolved. Our results indicate that while changes in atmospheric conditions can explain some of the variation in acoustic arrival time relative to the seismic signal arrivals, substantial residual time lag variations often still exist. Additionally, nonlinear propagation modeling results do not yield a change in the onset time of the acoustic arrival with source amplitudes comparable to (and larger) than Cleveland explosions. We find that a spectrum of seismic cross-correlation values between events and particle motion dip angles suggests that a varying explosion source depth within the conduit likely plays a dominant role in the observed variations in time lag. Explosion source depths appear to range from very shallow depths down to ∼1.5–2 km. Understanding the seismo-acoustic time lag and the subsequent indication of a variable explosion source depth may help inform explosion source modeling for Mount Cleveland, which remains poorly understood. We show that even with a single co-located seismic and acoustic sensor that does not always remain on scale, it is possible to provide meaningful interpretations of the explosion source depth which may help monitoring agencies understand the volcanic system.

火山爆炸会产生大量的，富含灰分的羽状物，对航空业构成极大危害，但通常很少有先兆地球物理信号。克利夫兰山是阿拉斯加阿留申弧（美国）上最活跃的火山之一，在2011年12月至2020年6月之间至少发生了65次爆炸。我们对克利夫兰山从爆炸开始的4年中的地震声信号进行了表征。在2014年安装了永久本地仪器时。尽管地震爆炸信号相似，但爆炸之间的声音信号却有所不同。一些爆炸声波形表现出单一的主压缩相位，而其他波形具有多重压缩。在距喷口约3 km的单个站点中，地震到达和声音到达之间的时滞变化很大（最多2.20 s），提示爆炸之间信号传播路径的变化。我们应用了多种方法来探索这种变化对时滞的潜在影响，这些时滞来自大气条件，非线性传播和导管内的源深度。在其他地方也观察到这种可变的时间滞后，但是通常无法解释。我们的结果表明，尽管大气条件的变化可以解释声波到达时间相对于地震信号到达的某些变化，但通常仍然存在大量的剩余时滞变化。此外，非线性传播建模结果不会使声波到达的开始时间发生变化，其震源振幅与克利夫兰爆炸相当（且更大）。我们发现，事件与粒子运动倾角之间的地震互相关值频谱表明，导管内变化的爆炸源深度可能在观察到的时滞变化中起主要作用。爆炸源的深度范围从很浅的深度到约1.5–2 km。了解地震声时滞和随后的变化的爆炸源深度指示可能有助于为克利夫兰山的爆炸源建模提供信息，而对此尚知之甚少。我们证明，即使使用一个并不会始终保持按比例放置的同一位置的地震和声音传感器，也可以对爆炸源的深度提供有意义的解释，这可能有助于监视机构了解火山系统。