Global observation of vertical‐CLVD earthquakes at active volcanoes

Abstract

[1] Some of the largest and most anomalous volcanic earthquakes have non-double-couple focal mechanisms. Here, we investigate the link between volcanic unrest and the occurrence of non-double-couple earthquakes with dominant vertical tension or pressure axes, known as vertical compensated-linear-vector-dipole (vertical-CLVD) earthquakes. We determine focal mechanisms for 313 target earthquakes from the standard and surface wave catalogs of the Global Centroid Moment Tensor Project and identify 86 shallow 4.3 ≤ M W ≤ 5.8 vertical-CLVD earthquakes located near volcanoes that have erupted in the last~100 years. The majority of vertical-CLVD earthquakes occur in subduction zones in association with basaltic-to-andesitic stratovolcanoes or submarine volcanoes, although vertical-CLVD earthquakes are also located in continental rifts and in regions of hot spot volcanism. Vertical-CLVD earthquakes are associated with many types of confirmed or suspected eruptive activity at nearby volcanoes, including volcanic earthquake swarms as well as effusive and explosive eruptions and caldera collapse. Approximately 70% of all vertical-CLVD earthquakes studied occur during episodes of documented volcanic unrest at a nearby volcano. Given that volcanic unrest is underreported, most shallow vertical-CLVD earthquakes near active volcanoes are likely related to magma migration or eruption processes. Vertical-CLVD earthquakes with dominant vertical pressure axes generally occur after volcanic eruptions, whereas vertical-CLVD earthquakes with dominant vertical tension axes generally occur before the start of volcanic unrest. The occurrence of these events may be useful for identifying volcanoes that have recently erupted and those that are likely to erupt in the future.

Submarine landslide triggered by volcanic eruption recorded by in situ hydrophone

“…The interpretation that the 2009 earthquakes were caused by magmatic intrusion centered on or near the volcano is also consistent with the fact that at least one of the earthquakes had a highly non-double-couple focal mechanism (Shuler et al, 2010) (Fig. 3A), similar to some earthquakes documented at other active volcanoes (Ekström, 1994;Shuler and Ekström, 2009).…”

The 8 October 2011 Earthquake at El Hierro (Mw 4.0): Focal Mechanisms of the Mainshock and Its Foreshocks

“…It has been shown that certain processes in volcanic regions, such as magmatic and hydrothermal fluid migration, may be accompanied by earthquakes with significant non-DC components (Shuler et al, 2013). However, results obtained in this work indicate the seismological observations both at local and regional distances can be well reproduced by a pure DC model for a shear failure on a planar fault.…”

Back‐arc extension in the Andaman Sea: Tectonic and magmatic processes imaged by high‐precision teleseismic double‐difference earthquake relocation

“…Shuler et al . [] found a strong correlation between the occurrence of vertical‐CLVD mechanisms and volcanic unrest, where vertical‐P mechanisms generally occur after eruptions. The location and timing of event O5 and vPC1 might therefore be indicative for volcanic processes such as deflating or collapse of a magma chamber in the center of segment C during the swarm.…”