The magnitude and intensity of the 60 CE Cretaio Tephra, the largest historical explosive eruption at Ischia caldera (Italy), was studied integrating field data and numerical modelling in order to reconstruct the dispersal of the fallout related to the climax phase of the eruption and characterize its physical parameters.

A field survey of the main fall unit (EUC) of Cretaio Tephra and its sampling was performed on the island, which is the proximal area of dispersal, and for the first time outcrops of this tephra were found southward on the Capri Island. The dataset is completed by a distal tephra sampled in the offshore and described in the literature, allowing the analysis of samples of intermediate and distal deposits. Grain size analysis of the samples collected on the island show bimodal distributions due to the presence of a ballistic component, especially in the most proximal sampling sites around the inferred and buried vent. Tails of fine ash in the distributions can be associated with settling enhanced by ash aggregation processes in the moisture-rich plume. Tephra dispersal was reconstructed using the HAZMAP tephra dispersal model by minimizing the difference between the simulations obtained exploring plausible ranges of eruption source parameters and the available thickness and grain-size measurements. Results show that the dispersal axis of EUC is to the south-southeast, the best guess for the total erupted volume of tephra is 0.075 km³, the plume height ranges between 5 and 13 km, for an average mass eruption rate (MER) of 10⁵ kg/s, hence a duration of the eruption of a few days. Considering an eruptive scenario given by the eruption parameters and diffusion coefficient of the Cretaio Tephra, together with a statistical set of wind profiles, HAZMAP modelling allowed us to generate tephra loading probability maps, needed to assess the impact of such an eruption at Ischia Island and the Neapolitan metropolitan area, pivotal for civil protection purposes.

Another important outcome of the study is that, for volcanic islands, the reconstruction of eruption parameters may benefit much more from the search of even few medial and distal offshore outcrops than from implementing the on-island proximal dataset only.

结合现场数据和数值模拟，研究了60 CE Cretaio Tephra（意大利伊斯基亚破火山口历史上最大的爆发性喷发）的强度和强度，以重建与喷发高潮期有关的尘埃散布并表征它的物理参数。

在Cretaio Tephra的主要坠落单元（EUC）上进行了野外调查，并在该岛上进行了采样，该岛是扩散的近端区域，并且首次在Capri岛上向南发现了该Tephra的露头。该数据集由在海上采样并在文献中进行描述的远侧提夫拉岩完成，可对中间和远侧沉积物的样品进行分析。由于存在弹道成分，岛上收集的样品的粒度分析显示出双峰分布，尤其是在推断和掩埋的喷口周围最近的采样点。分布中的细灰尾可能与富湿羽绒中灰分聚集过程增强的沉降作用有关。使用HAZMAP tephra弥散模型，通过最小化探索喷发源参数的合理范围与可用厚度和粒度测量所获得的模拟之间的差异，来重建Tephra弥散。结果表明，EUC的扩散轴位于东南偏南，对特发拉总喷发量的最佳猜测是0.075 km^{如图3所示}，羽流高度在5至13km之间，平均喷发速率（MER）为10 ⁵ kg / s，因此喷发的持续时间为几天。考虑到由Cretaio Tephra的喷发参数和扩散系数给出的喷发情况以及一组统计的风廓线，HAZMAP建模使我们能够生成tephra装填概率图，以评估这种喷发对伊斯基亚岛和伊斯基亚岛的影响。那不勒斯大都市区，对于民防目的至关重要。

这项研究的另一个重要成果是，对于火山岛而言，仅搜索很少的中部和远侧近海露头，比仅实施岛上近侧数据集可能会更多地受益于喷发参数的重建。