Volcano and Earthquake Hazards in the Crater Lake Region, Oregon

Volcano and Earthquake Hazards in the Crater Lake Region, Oregon

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Table of Contents

Complete Report (PDF) earthquake-hazard-report

 Cover

Summary

Introduction

Geologic setting of Crater Lake

Reawakening of Mount Mazama

Potential hazards from an eruption beneath Crater Lake

Factors controlling explosivity of eruptions in bodies of water

Pyroclastic surges

Ballistic blocks and other hazards of eruptions in the lake

Proximal hazard zones for explosive eruptions

Hazards of silicic eruptions outside the caldera

Hazards of lahars (volcanic debris flows) and their runout flows

Potential for lahars at Crater Lake

Definition of lahar hazard zone

Potential size and flow velocity of lahars at Crater Lake

Regional volcanism

Probability of a future volcanic eruption

Hazard zones for regional volcanoes

Events of high consequence but low probability

Another large volume or caldera-forming eruption?

Sudden gas release from Crater Lake

Catastrophic flood or lahar from drainage of Crater Lake

Protecting Crater Lake National Park and surrounding communities from volcano hazards

Earthquakes

Seismicity

West Klamath Lake fault zone

Slip rate and recurrence interval of the WKLFZ

Maximum earthquake on the WKLFZ

Cascadia subduction zone

Volcanic earthquakes

Landslides may cause large waves on Crater Lake

Subaqueous landslides

How large must an earthquake be to trigger landslides?

Waves generated by landslides into the lake

Waves generated by earthquakes

Preparing for an earthquake affecting the Crater Lake region

Acknowledgments

References

Glossary

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Illustrations

Plate 1. Map showing hazard zones, faults, and volcanic vents in the Crater Lake region ………. In pocket

Figure 1. Map showing faults and volcanic vents in the Crater Lake region

  1. Generalized geologic map of Mount Mazama and vicinity
  2. Geologic map of Crater Lake caldera floor
  3. Map showing earthquake epicenters and magnitudes

 

Tables

Table 1. Volume and flow properties of a hypothetical lahar at Crater Lake based on events at Mount St. Helens, Washington, and Raupehu Volcano, New Zealand

  1. Numbers of known basalt, basaltic andesite, and andesite volcanic vents and eruptive episodes outside Crater Lake caldera and exclusive of Mount Mazama between approximately latitudes 42°48’ and 43°05’
  2. Seismicity in the vicinity of Crater Lakre, Oregon
  3. Fault offsets (down-to-the-east) and average long-term slip rates along Annie Spring and Red Cone Spring faults
  4. Maximum earthquake magnitudes in the Crater Lake region
  5. Approximate minimum areas, thicknesses, and volumes of probable landslides at Crater Lake

* Technical terms which appear in bold italics in this report are defined in the glossary. A more comprehensive glossary, descriptions of types of volcanic activity in the Cascades, and more information on volcanoes can be found at the USGS Cascades Volcano Observatory World Wide Web site. URL: http://vulcan.wr.usgs.gov The book by Decker and Decker (1989) gives an illustrated, non -technical overview of volcanoes. The book by Francis (1993) is more technical and includes many case histories.

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