Throughout the 2018 eruption of Kīlauea volcano (Hawai‘i), episodic collapses of a portion of the volcano’s summit caldera produced repeated Mw 4.9–5.3 earthquakes. Each of these 62 events was characterized by a very‐long‐period (VLP) seismic signal (⁠>40 s⁠). Although collapses in the later stage of the eruption produced earthquakes with significant amplitude clipping on near‐summit broadband seismometers, the first 12 were accurately recorded. For these initial collapse events, we compare average VLP seismograms at six near‐summit locations to synthetic seismograms derived from displacements at collocated Global Positioning System stations. We show that the VLP seismic signal was generated by a radially outward and upward ramp function in displacement. We propose that at local distances the period of the VLP seismic signal is solely dependent on the duration of this ramp function and the instrument transfer function, that is, the seismic VLP is an artifact of the bandlimited instrument response and not representative of real ground motion. The displacement ramp function imposes a sinc‐function velocity amplitude spectrum that cannot be fully recovered through standard seismic instrument deconvolution. Any near‐summit VLP signals in instrument‐response‐corrected velocity or displacement seismograms from these collapse events are subject to severe band limitation. Similarly, the seismic amplitude response is not flat through the low‐frequency corner, for example, instrument‐response‐uncorrected seismograms scaled by instrument sensitivity are equally prone to band limitation. This observation is crucial when attempting to clarify the different contributions to the VLP source signature. Not accounting for this effect could lead to misunderstanding of the magmatic processes involved.

中文翻译：

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夏威夷基拉韦厄2018年破火山口坍塌期间的超长时期（VLP）地震伪像

在2018年的基拉韦厄火山（夏威夷）爆发期间，火山顶峰破火山口的局部坍塌导致4.9-5.3兆瓦地震反复发生。这62个事件中的每一个都具有很长一段时间（VLP）的地震信号（⁠> 40s⁠）。尽管在喷发的后期坍塌产生了地震，但在近峰宽带地震仪上出现了明显的幅度削波，但准确记录了前12个。对于这些初始坍塌事件，我们将六个近峰位置的平均VLP地震图与由并置的全球定位系统站的位移得出的合成地震图进行了比较。我们表明，VLP地震信号是由位移中的径向向外和向上倾斜函数生成的。我们建议在局部距离处，VLP地震信号的周期仅取决于该斜坡函数和仪器传递函数的持续时间，也就是说，地震VLP是带限仪器响应的伪像，并不代表真实的地面运动。 。位移斜坡函数强加了一个正弦函数速度振幅谱，该谱不能通过标准地震仪器反褶积法完全恢复。来自这些坍塌事件的仪器响应校正的速度或位移地震图中的任何接近峰值的VLP信号都受到严格的频带限制。同样，地震幅度响应在低频角处也不平坦，例如，由仪器灵敏度缩放的仪器响应未校正地震图同样容易受到频带限制。当试图澄清对VLP源签名的不同贡献时，此观察至关重要。不考虑这种影响可能导致对所涉及的岩浆作用过程的误解。