Seismology Response to the 2010 M7.2 El Mayor-Cucapah

Earthquake

Elizabeth Cochran11 Sept. 2011

Overview

1. Deployment• Instruments and people

2. Aftershock Relocation• Clouds to faults?

3. Lessons for the Next Response?• Objectives, Communication, Instrumentation, Sites

4 April 2010 M7.2 El Mayor-Cucapahaka ‘Baja Earthquake’

• Most of the rupture was south of the California-Mexico border

• Deployment Considerations:• Coordination between

US and Mexican researchers

• Customs issues for instrumentation

Seismic Deployment

• Deployment teams: UCR, UCSB and SDSU

• Instrumentation:• 5 UCR and 3 UCSB

station set-ups• Installed strong

(EpiSensors) and weak motion (L4) sensors

Early Aftershocks: April 4 – 6

Many thanks to the field teams!

Safety First!

Seismic Deployment:Stations installed between 4 April and 14 June 2010

Zoom Area

Aftershock Relocation:

Study Area

• 4000+ events within the study area

• 13 stations:• 8 temporary (5 UCR; 3

UCSB)• 5 SCSN

• Manually picked P and S arrivals

• And, cross-correlated for higher precision

SCSN Catalog Locations

K. Kroll, Masters Thesis, UCR

Relocation:Methods

HypoDD

• Uses automated, manual, and cross-correlation picks

• Provides good relative locations for well-clustered events

• Relative locations are not highly dependent on velocity model

Velocity Models UsedCVM-4 Imperial Valley,

10% higher, 10%, & 20% lower

Collapsing Method

• Defines clusters of events

• Principle component analysis of cluster to determine if is a point, line, or plane

• Moves the events within error estimates

Relocation:HypoDD Results

• HypoDD relocations suggest some NW and NE striking features

• However, features are still not very clear

Relocation:Collapsing Results

• NW and NE striking features are better defined

• Features that are consistent across the models are labeled

Zoom Area

See Poster B-46 for more results!

Aftershock Relocation in the Yuha Desert Following the 4 April 2010 M7.2 El Mayor-Cucapah Earthquake By K.A. Kroll, E.S. Cochran and K.B. Richards-Dinger

Lessons for the Next Response

Successful response requires:1. Known science objectives

2010

US-side covered a limited portion of the aftershock zone, no simple surface rupture, edge of the SCSN.

Goal: Use relocated seismicity to better define structures in the region

Future

High-resolution studies of large aftershocks?

Fault zone studies?

Site response across an urban area?

Not clear if it is possible to fully define objectives in advance?

Lessons for the Next Response

Successful response requires: Known science objectives

2. Rapid communication between groups interested in deployment

Successful coordination through the SCEC Response Wiki

Ensure information is relayed to all potential volunteers (not just PIs)

Communication between groups during a large event (satellite phones, text message)?

Lessons for the Next Response

Successful response requires: Known science objectives Rapid communication between groups interested in

deployment

3. Available equipment and locations2010

Only a few stations were needed; telemetry was not reliable

Future

More equipment needed for a large quake; SCEC RAMP equipment needs modernizing

Real time data integration into the network; important for rapid event detection, aftershock forecasting, research

Often difficult to find adequate locations (security, power, etc.)

Lessons for the Next Response

Successful response requires: Known science objectives Rapid communication between groups interested in

deployment× Available equipment, including telemetry

• Urban Ramp• Clear view of sky for GPS

timing is often an issue• Small footprint makes

building/land owners more comfortable

• Smaller AC Power supply with charge controller and small battery

• Coupling sensor to Earth for ground response observations

• SSI – Free Field or building response

• Remote Ramp• Secure location• Low power, autonomous,

with ability to telemeter state of health at a minimum

• Often marginal or no land-based communications service

• Costly to maintain if the sites have to be visited regularly

• Costly to integrate the data into the regional network after the fact.

RAMP Needs

From Steidl, Seismic Instrumentation Workshop

The End