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Systematic Measurements of Parameters During Earthquake Swarms

Description: 

The identification of processes causing earthquake swarms are long-standing problems in seismology. We are engaged in an ongoing comprehensive and systematic approach that examines a variety of parameters. Here we summarize recent results which have not been previously published. We investigated the difference in magnitude M between the largest and second largest events, which we call M1-M2. Large samples (67-174 swarms) of swarms in tectonic and volcanic areas (teleseismic data) each had similar distributions and variances and the same means of 0.16 M units. No swarms were found with M1-M2 equal to 0.7, which suggests a break in scaling. M1-M2 is systematically larger as M1 get larger, which suggests variability of conditions in the source regions. Swarm durations are longest for swarms on megathrusts, and shortest at volcanoes, although distributions overlap. The largest event occurs late in volcanic swarms, suggesting a growing source size. This trend is not observed for mid-ocean ridge swarms. A plot of number of events in swarms versus number of swarms shows two branches (sub-parallel trends), suggesting two dominant processes. An updated study of volcanic swarms that follow the Generic Volcanic Earthquake Swarm Model (GVESM) using local data show that the peak rate occurs near the onset of low-frequency events. This suggests that the peak rate is the culmination of development of a system of cracks, which then facilitate fluid (water, gas, or magma) movement. Overall, the suite of observations and measurements suggests that there are several mechanisms or processes involved in earthquake swarms.

Session: Advances in Operational and Research Analysis of Earthquake Swarms -II

Type: Oral

Date: 5/3/2024

Presentation Time: 04:45 PM (local time)

Presenting Author: Stephen

Student Presenter: No

Invited Presentation: 

Authors