2024 Alaska Seismicity Summary

The Alaska Earthquake Center reported 39,836 seismic events in Alaska and neighboring regions in 2024. The largest earthquakes were two magnitude 6.3 events that were part of a swarm of M6 events on December 8-9 in the Andreanof Islands region of Alaska. The first occurred on December 8 at 19:57:07 UTC, and the second occurred at 00:15:30 on December 9, followed by an M6.1 23 minutes later. Other strong earthquakes include two M6.0 events, one on May 19 and one on July 19, both south of Yunaska Island in the Islands of Four Mountains region of the Aleutians, and the strongest mainland earthquake, an M5.9, off the coast of Port Alexander in Southeast Alaska on January 12. We continued to monitor the 2020 M7.8 Simeonof sequence, but all other previous sequences and swarms have dropped below one event per day and are no longer being tracked. Numerous short-lived swarms occurred in 2024 and will be discussed below.1. Abstract 2. Introduction 3. Notable seismic events 3.1. December 8-9 Adak Island Swarm 3.2. January 19 M5.3 Salcha Earthquake 3.3. Kaktovik Swarm 3.4. Ulaneak Creek Swarm 3.5. Landslides 3.6. Volcanic Events 4. Ongoing aftershock sequences and swarms 4.1. 2020 M7.8 Simeonof aftershock sequence 5. Glacial seismicity and Wright Glacier cluster 6. Acknowledgments 7. Reference

Alaska Earthquake Center Quarterly Technical Report October-December 2024

This series of technical quarterly reports from the Alaska Earthquake Center (AEC) includes detailed summaries and updates on Alaska seismicity, the AEC seismic network and stations, fieldwork, our online presence, public outreach, and lists publications and presentations by AEC staff. Multiple AEC staff members contributed to this report.1. Introduction 2. Seismicity 3. Alaska Geophysical Network 4. Data quality assurance 4.1 Seismic data 4.2 Environmental data 5. Real-time earthquake detection system 6. Computer systems 6.1 Computer resources 6.2 Waveform storage 6.3 Metadata 6.4 Software development 7. Fieldwork 7.1 October 7.2 November 7.3 December 8. Website, social media, and outreach 8.1 Website 8.2 X 8.3 Facebook 8.4 Instagram 8.5 LinkedIn 8.6 K-12 and community outreach 8.7 Workforce development 9. Publications and presentations 9.1 Publications 9.2 Public presentations 9.3 GI Geoscience lunch seminar talks 10. References Appendix A: Data availability for broadband stations from the AK network Appendix B: Gaps for broadband stations from the AK network Appendix C: 2025 strategic prioritie

Alaska Earthquake Center Quarterly Technical Report July-September 2024

This series of technical quarterly reports from the Alaska Earthquake Center (AEC) includes detailed summaries and updates on Alaska seismicity, the AEC seismic network and stations, fieldwork, our online presence, and lists publications and presentations by AEC staff. Multiple AEC staff members contribute to this report. It is issued within 1-2 months after the completion of each quarter Q1: January-March, Q2: April-June, Q3: July-September, and Q4: October-December. The first report was published for January-March, 2021.1. Introduction 2. Seismicity 3. Alaska Geophysical Network 4. Data quality assurance 4.1 Seismic data 4.2 Environmental data 5. Real-time earthquake detection system 6. Computer systems 6.1 Computer resources 6.2 Waveform storage 6.3 Metadata 6.4 Software development 7. Fieldwork 8. Social media and outreach 8.1 Website 8.2 X 8.3 Facebook 8.4 Instagram 8.5 LinkedIn 28 8.6 K–12 and community outreach 8.7 Workforce development 9. Publications and presentations 9.1 Publications 9.2 Public presentations 9.3 GI Geoscience lunch seminar talks 10. References Appendix A: Data availability for broadband stations from the AK network. Appendix B: Gaps for broadband stations from the AK network

Alaska Earthquake Center Quarterly Technical Report October-December 2021

This series of technical quarterly reports from the Alaska Earthquake Center (AEC) includes detailed summaries and updates on Alaska seismicity, the AEC seismic network and stations, field work, our social media presence, and lists publications and presentations by AEC staff. Multiple AEC staff members contributed to this report. It is issued in the following month after the completion of each quarter Q1: January-March, Q2: April-June, Q3: July-September, and Q4: October-December.1. Introduction 2. Seismicity 3. Field network 4. Data Quality assurance 5. Real-time earthquake detection system 6. Computer systems 6.1 Computer resources 6.2 Waveform storage 6.3 Metadata 6.4 Software development 7. Fieldwork 8. Social media and outreach 8.1. Website 8.2. Twitter 8.3. Facebook (Page) 8.4. Facebook (Group) 9. Publications and presentations 9.1. Publications 9.2. Public Presentations 9.3. Lunch Seminar Talks 10. References Appendix A: Data availability for broadband stations from the AK network. Appendix B: Gaps for broadband stations from the AK network

Supplemental Material: Receiver function analyses of Uturuncu volcano, Bolivia and vicinity

Geosphere, February 2018, v. 14, p. 50-64, doi:10.1130/GES01560.1, Supplemental Table S2. Lists teleseismic earthquakes used in the receiver function analysis for Uturuncu Volcano. Hypocentral locations are given in latitude, longitude, depth in km, and location name, as well as time of earthquake in UTC. Xs denote the use of the earthquake for the 2.5 Hz and 5.0 Hz Gaussian filters, as well as the use of the P and/or PP phase arrivals for each event

Supplemental Material: Receiver function analyses of Uturuncu volcano, Bolivia and vicinity

Geosphere, February 2018, v. 14, p. 50-64, doi:10.1130/GES01560.1, Supplemental Figures. Include the results of the CCP stacking program for a 2.5 Hz Gaussian filter with 15 x 15 km bin spacing, as well as the results of the 2.5 Hz Gaussian filter with a 10 × 10 km bin spacing and various weighting parameters

Supplemental Material: Receiver function analyses of Uturuncu volcano, Bolivia and vicinity

Geosphere, February 2018, v. 14, p. 50-64, doi:10.1130/GES01560.1, Supplemental Table S1. Lists the names of the seismic stations used in the PLUTONS array at Uturuncu Volcano, as well as the times of deployment and location information

A Seismic Investigation of Uturuncu Volcano and the Lazufre Volcanic Complex

The following dissertation is a study of three seismological techniques used to determine the geophysical properties of two large, inflating magma bodies in the upper crust in South America: one under Uturuncu volcano and one beneath Lastarria and Cordon del Azufre volcanoes. First, I use the method of teleseismic receiver functions to image the top and bottom of the magma body beneath Uturuncu volcano. Depths to the top of this body vary between 6 and 12 km below sea level, while depths to the bottom vary between 13 and 22 km below sea level, with the thickness ranging from 6 to 15 km. Then, I compute hypocenters and classify the earthquakes occurring between Lastarria and Cordon del Azufre volcanoes to determine if a magma body between them is priming for eruption or if it may be feeding a shallower magma chamber beneath Lastarria. My classification scheme consisted of five types of seismic events: volcano-tectonic, long period type 1, long period type 2, hybrid, and unknown. The majority of these events are above 10 km below sea level, and most are near Lastarria. I determine that this seismic activity is due to mobile gases and fluids. Finally, I use an attenuation method to study the heterogeneity of the crust between Uturuncu volcano and the magma body beneath it. The assumptions of the method used are undermined by the variability of the earthquake sources and their spectra as well as by extreme geological heterogeneity of this location

2023 Alaska Seismicity Summary

The Alaska Earthquake Center reported 45,546 seismic events in Alaska and neighboring regions in 2023. The largest earthquake was a magnitude 7.2 event that occurred on July 16 in the Alaska Peninsula region. It was a late aftershock of the 2020 M7.8 Simeonof Earthquake. Other strong earthquakes include the October 16 M6.4 and December 21 M6.1 earthquakes in the Andreanof Islands region of the Aleutian Islands. The largest earthquake in mainland Alaska, magnitude 5.4, occurred in the lower Cook Inlet region on March 19. We continued to monitor ongoing activity within the 2018 M7.1 Anchorage, 2018 M6.4 Kaktovik, 2018 M7.9 Offshore Kodiak, 2020 M7.8 Simeonof, and 2021 M8.2 Chignik aftershock sequences, the Purcell Mountains earthquake swarm, and the Wright Glacier cluster northeast of Juneau. All aftershock sequences continued to slow down compared to the previous years.1. Abstract 2. Introduction 3. Notable seismic events 3.1. October 16 M6.4 and December 21 M6.1 earthquakes in Andreanof Islands 3.2. March 19 M5.3 earthquake in southern Cook Inlet 3.3. Landslides 3.4. Volcanic events 4. Ongoing aftershock sequences and swarms 4.1. 2018 M7.1 Anchorage aftershock sequence 4.2. 2020 M7.8 Simeonof aftershock sequence 5. Glacial seismicity and Wright Glacier cluster 6. Acknowledgments 7. Reference

Q-values and Attenuation of the Shallow Crust Under Uturuncu Volcano, Bolivia

Uturuncu Volcano, located in the Altiplano-Puna region of the central Andes, near the border of Bolivia and Chile, has been shown to be inflating at a rate of 1-2 cm/yr over an area that is about 70 km wide. The PLUTONS project deployed 28 broadband seismometers around Uturuncu from April 2009 to October 2012. Several thousand shallow (depth \u3c 20 km) local earthquakes were recorded. Attenuation of seismic waves along travel paths for these local crustal earthquakes can be measured by calculating Q-values, which we have performed using the method of single station spectral ratios by Frankel (1982). Large scatter in the Q-values for various distances and travel times appear to be a function of variations in source depth, focal mechanism, and back azimuth. Preliminary Q-values were calculated for azimuths in 30° increments in sectors around each station. Estimates for Q range from about 60 to 700, with many showing a low Q in the direction of the summit from each station. This suggests that the volcanic pile is more highly attenuating than the surrounding crust