Fault friction is central to understanding earthquakes, yet laboratory rock mechanics experiments are restricted to, at most, meter scale. Questions thus remain as to the applicability of measured frictional properties to faulting in situ. In particular, the slip-weakening distance dc strongly influences precursory slip during earthquake nucleation, but scales with fault roughness and is challenging to extrapolate to nature. The 2018 eruption of K̄ılauea volcano, Hawaii, caused 62 repeatable collapse events in which the summit caldera dropped several meters, accompanied by MW 4.7 to 5.4 very long period (VLP) earthquakes. Collapses were exceptionally well recorded by global positioning system (GPS) and tilt instruments and represent unique natural kilometer-scale friction experiments. We model a piston collapsing into a magma reservoir. Pressure at the piston base and shear stress on its margin, governed by rate and state friction, balance its weight. Downward motion of the piston compresses the underlying magma, driving flow to the eruption. Monte Carlo estimation of unknowns validates laboratory friction parameters at the kilometer scale, including the magnitude of steady-state velocity weakening. The absence of accelerating precollapse deformation constrains dc to be ≤10 mm, potentially much less. These results support the use of laboratory friction laws and parameters for modeling earthquakes. We identify initial conditions and material and magma-system parameters that lead to episodic caldera collapse, revealing that small differences in eruptive vent elevation can lead to major differences in eruption volume and duration. Most historical basaltic caldera collapses were, at least partly, episodic, implying that the conditions for stick–slip derived here are commonly met in nature.

断层摩擦是理解地震的核心，但实验室岩石力学实验最多只能达到米级。因此，关于测量的摩擦特性对原位断层的适用性仍然存在问题。特别是滑移减弱距离dC强烈影响地震成核过程中的前兆滑动，但随着断层粗糙度的增加，很难推断出自然。2018 年夏威夷 K̄ılauea 火山喷发导致 62 次可重复的崩塌事件，其中山顶破火山口下降数米，伴随米W4.7 至 5.4 级甚长周期 (VLP) 地震。全球定位系统 (GPS) 和倾斜仪器对塌陷的记录非常好，代表了独特的自然千米级摩擦实验。我们模拟一个活塞坍塌成岩浆库。活塞底部的压力和边缘上的剪切应力，由速率和状态摩擦控制，平衡了它的重量。活塞的向下运动压缩了下面的岩浆，推动流向喷发。未知数的蒙特卡罗估计验证了千米尺度的实验室摩擦参数，包括稳态速度减弱的幅度。没有加速预塌陷变形约束dC 成为 ≤10毫米，可能要少得多。这些结果支持使用实验室摩擦定律和参数来模拟地震。我们确定了导致偶发性破火山口坍塌的初始条件以及材料和岩浆系统参数，揭示了喷发口高度的微小差异可能导致喷发量和持续时间的重大差异。大多数历史上的玄武质破火山口坍塌至少部分是偶发的，这意味着这里产生的粘滑条件在自然界中普遍存在。