Google Earth

Implementation of the ShakeMap System in Alaska

by Artak Martirosyan

Geophysical Institute, University of Alaska Fairbanks

ShakeMap

The USGS ShakeMap system is a tool for the real-time generation of ground-shaking maps following significant earthquakes.

ShakeMaps provide vital information within minutes after an earthquake to emergency response agencies, the media and the general public.

ShakeMaps are produced on the basis of observed ground motion values (peak velocities, peak accelerations, and spectral accelerations) and complemented by calculated values using empirical attenuation relationships.

ShakeMap Workflow at AEIC

Alaska Seismic Network

AEIC

Antelope Real-Time System

Parametric and Ground Shaking Data

ShakeMap System

ShakeMap Web Pages

DATA

Observations for ShakeMaps are collected from more than 80 broadband and 25 strong motion stations throughout the state.

Ground motion grids are based on maximum peak ground accelerations and velocities of two horizontal components.

Currently, ShakeMaps are produced for events with magnitudes greater that M3.5 with at least 10 associated arrival picks and calculated MMI greater than 2.0 at the epicenter.

Map of Seismic Stations

ShakeMap Methodology

The ShakeMap triggering and production is based on the Antelope system used for real-time seismic operations at AEIC.

The ShakeMap generation sequence is triggered once a new event above certain magnitude appears in the real-time event database.

The first ShakeMap is automatically generated within 1-2 minutes after that, and then several updates may be automatically issued if new data becomes available from different sources.

Analyst-reviewed ShakeMaps are generated for alarm events after the revision of the automatic solutions, usually within 25 to 45 min of the origin time.

A cancellation script is activated if an updated hypocenter is no longer eligible for ShakeMap.

A final version of ShakeMap is manually produced for larger events, if necessary, in order to utilize any additional information, including extended source geometry.

REAL-TIME SYSTEM ARCHITECTURE

Summary Database

AEIC ShakeMap Homepage

NEAR REAL-TIME SHAKEMAPS

Vs30 Grid

The site corrections are based on the average shear-wave velocity values for the uppermost 30 meters (Vs30).

Vs30 values are derived from the slope of the topography.

Correlation of Vs30 and Site Response in Anchorage

Geology Map

Attenuation Relationships

Boore et al. (1997) model is used for the crustal events with M>5.3.

Youngs et al. (1997) model is used for subduction-zone events.

ShakeMap Small Regression model for shallow events with M<=5.3.

Observed and Predicted PGA During the Denali M7.9 Earthquake

SCENARIO SHAKEMAP

M7.1 earthquake on the Border Ranges Fault near Anchorage

Scenario ShakeMaps represents the expected ground motions from hypothetical earthquakes.

Earthquake scenarios play an important role in planning and coordinating emergency response and conducting training exercises based on realistic situations.

Thank You!

Slide 1

AM

2007-03-23T14:12:18

Glenn Thompson

Glenn Thompson