A Proposed Seismic Microzonation Study of the City of Santo Domingo,

Dominican Republic Jay Pulliam1, Victor Huérfano2, Michael Schmitz3, Carlos Valdés-Gonzalez4,

Richie Robertson5, Lyndon Brown6, Eugenio Polanco7

1 Baylor University USA; 2Puerto Rico Seismic Network; 3FUNVISIS, Venezuela; 4UNAM, Mexico City, Mexico; 5Seismic Research Centre, Trinidad & Tobago; 6Earthquake Unit, UWI

Mona, Jaimaca; 7Instituto Sismología Universitario, UASD, Dominican Republic

PLUS! The Puerto Rico Seismic Network:

Earthquake and Tsunami Monitoring

The mission of the Puerto Rico Seismic Network (PRSN) is to rapidly determine the location and size of all earthquakes and tsunamis in the PRSN’s Area of Responsibility (AOR) and to immediately disseminate this information to concerned agencies, scientists, and the general public. The PRSN compiles and maintains an extensive seismic database of earthquake parameters, continuous waveforms (earthquakes, GPS, and sea level) and their effects, which serves as a foundation for basic and applied earth science and oceanography research in Puerto Rico and the Caribbean.

PRSN MISSION

The Puerto Rico Seismic Network:

Earthquake and Tsunami Monitoring

PRSN VIRTUAL NETWORK IU: IRIS/USGS II : IRIS/IDA CU: USGS Caribbean PR: PRSN/PRSM, Puerto Rico UA: Aruba Meteorological Agency G : Geoscope GE: Geofone MO: Montserrat Volcano Observatory NA: KMNI Antilles DR: ISU Dominican Republic, UT UC: Colima University, Mexico SV: SNET, El Salvador NI: INETER, Nicaragua OV: OVSICORI, Costa Rica PA: Volcan Baru Network, Panama TR: West Indies Seismic Research Center CM: Colombian National Seismological Network CN: Canadian Seismic Network BL : Brazil Seismic Network MG: National Seismological Service of Mexico CY: Cayman Island

CURRENT REAL TIME EARTHQUAKE MONITORING

Current real time tsunami monitoring

PRSN SEISMIC CATALOGUE (AOR)

PRSN SEISMIC CATALOGUE (AOR)

ShakeMap in PUERTO RICO

ShakeMap

• Generates maps of the spatial distribution of peak ground-motions (acceleration, velocity, and spectral response) as well as a map of instrumentally derived seismic intensities.

• These maps provide a rapid visual (and quantitative) estimate of the extent of potentially damaging shaking during an earthquake and can be used for emergency response, loss estimation, and for public information through the media.

• The frequency and amplitude dependence of site amplification on local site geology (average 30-m depth shear velocity) is still a rapidly evolving area of study.

Magnitude 7.0 - HAITI REGION Tuesday, January 12, 2010 at 21:53:09 UTC

WC/ATWC

PTWC

NEIC

ISC

DMC

ASL

IDA

REGIONAL NETWORKS

NOAA

CURRENT REAL TIME DATA SHARING

UNAVCO

COCONet GPS Network

88 representatives from 22 different countries

• 14 grad students or postdocs

• 27 professors

• 15 people primarily associated with networks or seismology research

• 20 “others”

Among the 20 “others” are representatives from

• World Bank

• UNISDR Americas

• UNDP

• NOAA/NWS

• USAID

• UNAVCO

• IRIS

• CTBTO

• NSF

• Haiti • Dominican

Republic • Guadeloupe • Martinique • Jamaica • Puerto Rico • Trinidad & Tobago • British Virgin

Islands • Puerto Rico • Venezuela • Colombia

• Guatemala • Costa Rica • Honduras • Nicaragua • Mexico • Panama • United Kingdom • United States • Norway • Germany

Sponsored by U.S. National Science Foundation, US Agency for International Development, American Geophysical Union

Santo Domingo • Population of 3.3 M • Largest city in the

Caribbean by population • Subject to severe

earthquakes • Oldest European

settlement in the western hemisphere—has been built and re-built, streams re-directed, etc.

• Area of metropolitan area is ~10 km x ~20 km.

Figure from Bilham, Lessons from the Haiti earthquake, Nature 463, 878-879 (18 February 2010), doi:10.1038/463878a

The toll of the 2010 Haiti quake is more than twice that of any previous magnitude 7.0 event, and the fourth worst since 1900

Seismic Microzonation

• The process of subdividing potential earthquake prone area into zones with respect to some geophysical characteristics of the sites such as ground shaking, susceptibility to liquefaction, landslide or rock fall hazard, or earthquake-related flooding, so that seismic hazards at different locations within the area can be correctly identified.

• “Site Characterization” – The process of estimating the response of soil layers to earthquakes and thus the variation of earthquake characteristics on the ground surface.

• Provides the basis for site-specific risk analysis, which can assist in the mitigation of earthquake damage.

• A preliminary phase of earthquake risk mitigation studies.

Methods

• Dynamic characteristics of site such as predominant period, amplification factor, shear wave velocity, standard penetration test (SPT) values can be used for seismic microzonation purposes.

• Shear wave velocity measurements and standard penetration tests are generally expensive and are not feasible to be carried out at large number of sites for the purpose of microzonation (“active-source techniques).

• “Passive-source” techniques can also be used to determine the dynamic properties of soil strata. Measurements are easy to perform, inexpensive, and can be carried out in places with low seismicity rates.

• Ambient noise (also called “microtremor”) analysis

– Horizontal-vertical spectral ratio (HVSR) modeling (e.g., Nakamura, 1989)

– Spatial autocorrelation (SPAC) array processing method (e.g., Asten, 2006)

– F-k methods (e.g., Louie, 2001)

Comparison of Methods

Table from Asten, M.W., and Boore, D.M., eds., Blind comparisons of shear-wave velocities at closely spaced sites in San Jose, California: U.S. Geological Survey Open-File Report 2005-1169. [available on the World Wide Web at http://pubs.usgs.gov/of/2005/1169/ ].

Which method is best?

It depends on • What information you need • Which subset of information you need to be most

reliable (e.g., average Vs, ability to resolve layering (especially low-velocity layers), depth of penetration, systematic bias if any in velocity estimates)

• Logistics – Funding limitations – Skill sets and personnel available – Operational limitations (e.g., can you use active

sources?)

Results

Table from Asten, M.W., and Boore, D.M., eds., Blind comparisons of shear-wave velocities at closely spaced sites in San Jose, California: U.S. Geological Survey Open-File Report 2005-1169. [available on the World Wide Web at http://pubs.usgs.gov/of/2005/1169/ ].

800 Observation Points in Santo Domingo

Logistics

• Santo Domingo’s metropolitan area is ~10 km x ~20 km.

• A grid in which observation points are spaced 500 m apart would produce 800 observations points.

• A team of two skilled people can make observations at 40 sites in three days.

• 20 teams would be able to acquire all the data in three days.

• Alternatively (in order to reduce logistics of vehicles, equipment, etc.), two groups of 10 teams could alternate tasks over 6 days: one group records data while the other group processes data.

Questions or Comments?

SPAC

Elham Shabani, et al., 2011. The SPAC Method for a Finite M-Station Circular Array Using Horizontally Polarized Ambient Noise, Bulletin of the Seismological Society of America, Vol. 101, No. 2, pp. 544–557, April 2011, doi: 10.1785/0120090213

(a) SPAC coefficient obtained for vertical components of microtremor records in the array; the black dots and error bars are the samples selected. (b) The Rayleigh-wave dispersion curve.