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Cape Mendocino, CA Earthquakes, April 25 & 26, 1992

Entry ID: gov.noaa.ngdc.G01209

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Summary

Abstract: ABSTRACT: On April 25, 1992, a magnitude 7.1 earthquake occurred in the Cape Mendocino area. Two additional earthquakes, magnitudes 6.6 and 6.7 occurred the next morning. The first earthquake was located six miles north of Petrolia, California, in a sparsely populated part of southwestern Humboldt County. Five small communities were located within a 50 mile radius of these events: Honeydew, ... Petrolia, Rio Dell, Scotia, and Ferndale. This slide set illustrates the effects and damage of a moderately large earthquake and moderate aftershocks on this sparsely settled area.Statistics - The first earthquake was located six miles The main earthquake came immediately after a Saturday morning parade at Ferndale. Horses reportedly became spooked during the parade (before the earthquake), but riders attributed it to flags fluttering in the wind along the parade route.Seismicity and Geology - The Cape Mendocino region of California's north coast is one of the most seismically active regions in the conterminous United States. This seismic zone coincides with the Mendocino Triple Junction, a tectonically unstable area where three tectonic plates join together.The earthquake of April 25 is exceptional for several reasons. It generated a tsunami that was recorded along the West Coast and measurable in the Hawaiian Islands. It also produced distinct uplift (maximum uplift = 1 m) along a 25-km-long section of the coastline. The April 25 event was the largest historic earthquake in this region with an epicenter clearly located on land, and the only damaging event that may have resulted from thrust faulting along the Cascadia subduction zone.Earth Effects - A broad zone of ground fractures, coastal uplift, and elevation changes are the only surface changes to indicate the location and tilt of the fault plane. Strong ground shaking during the earthquakes triggered numerous landslides in steep mountainous areas. A landslide at Scotia Bluffs (south of Scotia) temporarily interrupted traffic on the North Coast Railroad. Tension cracks, due to soil compaction and downhill slumping, restricted traffic on the Mattole Road between Honeydew, Petrolia, and Ferndale. Liquefaction took place in modern deposits of the Mattole River between Petrolia and Honeydew, and in the flood-plain deposits of the Eel and Salt Rivers. Soils liquefy when ground water near the surface is forced between the grains of sand during an earthquake. The sandy soil behaves like a very thick liquid. Structures then settle or tip in the liquefied soil, or are ripped apart as the ground spreads laterally or flows. Sand blows result from the eruption of liquefied sediment from the subsurface on to the ground. The eruption of liquefied sediment is facilitated by fissures in the ground, which are also produced by strong shaking during an earthquake.Damage - Collectively, these shocks caused significant damage to older structures in the sparsely populated, mountainous, epicentral region. The earthquake caused 98 injuries and moderate damage in Humboldt County. Losses topped $66 million. Single- and double-story, wood-frame houses and commercial buildings were the most common type of structures in the epicentral region, where lumber is the principal industry. Many foundations were the pier and post type, providing little resistance to lateral ground shaking. The earthquakes jarred many older homes off their foundations.

CURRENTNESS REFERENCE: Publication Date

Purpose: PURPOSE: Make available Damage Photos for research and education

Related URL

Link: GET DATA

Description: View all slides in this slide set

Geographic Coverage

(Click for Interactive Map)

Spatial coordinates

N: 40.35

S: 40.2

E: -124.02

W: -124.16

Data Set Citation

Dataset Originator/Creator: DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce (comp)

Dataset Title: Cape Mendocino, CA Earthquakes, April 25 & 26, 1992

Dataset Release Date: 1994

Dataset Release Place: Boulder, CO

Dataset Publisher: National Geophysical Data Center

Version: First

Other Citation Details: http://www.ngdc.noaa.gov/hazard/hazards.shtml

Online Resource: http://map.ngdc.noaa.gov/website/seg/hazards/viewer.htm

Temporal Coverage

Start Date: 1992-04-25

Stop Date: 1992-04-26

Location Keywords

CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > CALIFORNIA > CAPE MENDOCINO

CONTINENT > NORTH AMERICA > UNITED STATES OF AMERICA > CALIFORNIA > HUMBOLDT

Science Keywords

SOLID EARTH > TECTONICS > EARTHQUAKES > EARTHQUAKE OCCURRENCES

SOLID EARTH > TECTONICS > PLATE TECTONICS > FAULT MOVEMENT

ISO Topic Category

GEOSCIENTIFIC INFORMATION

Project

ESIP > Earth Science Information Partners Program

Quality ATTRIBUTE ACCURACY REPORT: unknown

LOGICAL CONSISTENCY REPORT: unknown

COMPLETENESS REPORT: unknown

LINEAGE/PROCESS STEP:
PROCESS DESCRIPTION: slide set is out of stock and will not be produced again. Distribution has been modified and the SOP for the 35mm slide has been removed.
PROCESS DATE: 20060607

Access Constraints ACCESS CONSTRAINTS: None

DISTRIBUTION LIABILITY: While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.

CUSTOM ORDER PROCESS: Contact Data Center

Use Constraints None

Ancillary Keywords

WDC/SEG, BOULDER > World Data Center for Solid Earth Geophysics, Boulder

Geoscientific Information

DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce

Data Set Progress

COMPLETE

Data Center

National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce

Data Center URL: http://www.ngdc.noaa.gov/
Dataset ID: ______Document ____

Data Center Personnel
Name: NGDC USER SERVICES Phone: (303) 497-6826 Fax: (303) 497-6513 Email: ngdc.info at noaa.gov Contact Address: NOAA/NESDIS/NGDC E/GC 325 Broadway City: Boulder Province or State: CO Postal Code: 80305-3328 Country: USA

Distribution

Distribution Size: 25100

Distribution Format: TIFF

Fees: None $195.00/$145.00 plus handling and shipment outside the USA

Distribution Format: TIFF

Fees: None $195.00/$145.00 plus handling and shipment outside the USA

Personnel

JOY IKELMAN

Role: TECHNICAL CONTACT

Phone: 303-497-6419

Fax: 303-497-6513

Email: Joy.A.Ikelman at noaa.gov

Contact Address:

NOAA/NESDIS/NGDC

Mail Code E/GC4

325 Broadway

City: Boulder

Province or State: CO

Postal Code: 80303

Country: USA

KELLY STROKER

Role: DIF AUTHOR

Phone: (303) 497-4603

Fax: (303) 497-6513

Email: kelly.stroker at noaa.gov

Contact Address:

NOAA/NESDIS/NGDC E/GC1 325 Broadway

City: Boulder

Province or State: CO

Postal Code: 80305-3328

Country: USA

Creation and Review Dates

DIF Creation Date: 2008-01-18

Last DIF Revision Date: 2011-04-14

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