Abstract. The 2017 Mw 7.1 PueblaâMorelos intraslab
earthquake (depth: 57âkm) severely hit PopocatĂ©petl Volcano, located
âŒâ70âkm north of the epicenter. The seismic shaking triggered shallow
landslides on the volcanic edifice, mobilizing slope material saturated by
the 3âd antecedent rainfall. We produced a landslide map based on a
semi-automatic classification of a 50âcm resolution optical image acquired
2Â months after the earthquake. We identified hundreds of soil slips and
three large debris flows for a total affected area of 3.8âkm2.
Landslide distribution appears controlled by the joint effect of slope
material properties and topographic amplification. In most cases, the
sliding surfaces correspond with discontinuities between pumice-fall and
massive ash-fall deposits from late Holocene eruptions. The largest
landslides occurred on the slopes of aligned ENEâWSW-trending ravines, on
opposite sides of the volcano, roughly parallel to the regional maximum
horizontal stress and to volcano-tectonic structural features. This suggests
transient reactivation of local faults and extensional fractures as one of
the mechanisms that weakened the volcanic edifice and promoted the
largest slope failures. The material involved in the larger landslides
transformed into three large debris flows due to liquefaction. These debris
flows mobilized a total volume of about 106âm3 of material
also including large wood, were highly viscous, and propagated up to 7.7âkm
from the initiation areas. We reconstructed this mass wasting cascade by
means of field evidence, samples from both landslide scarps and deposits,
and analysis of remotely sensed and rainfall data. Although
subduction-related earthquakes are known to produce a smaller number of
landslides than shallow crustal earthquakes, the processes described here show how an unusual intraslab earthquake can produce an exceptional impact
on an active volcano. This scenario, not related to the magmatic activity of
the volcano, should be considered in multi-hazard risk assessment at
Popocatépetl and other active volcanoes located along volcanic arcs.