Prepared in cooperation with the PUERTO RICO ELECTRIC POWER AUTHORITY StratigraphyStratigraphy,, Structure, and Geologic and Coastal Hazards in the Peñuelas to Salinas Area, Southern Puerto Rico: A Compendium of Published Literature Open-File Report 2007-1259 U.S. Department of the Interior U.S. Geological Survey Stratigraphy, Structure, and Geologic and Coastal Hazards in the Peñuelas to Salinas Area, Southern Puerto Rico: A Compendium of Published Literature By Jesús Rodríguez-Martínez Prepared in cooperation with the Puerto Rico Electric Power Authority Open-File Report 2007–1259 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior DIRK KEMPTHORNE, Secretary U.S. Geological Survey Mark D. Myers, Director U.S. Geological Survey, Reston, Virginia: 2007 For product and ordering information: World Wide Web: http://www.usgs.gov/pubprod Telephone: 1-888-ASK-USGS For more information on the USGS--the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment: World Wide Web: http://www.usgs.gov Telephone: 1-888-ASK-USGS Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report. Suggested citation: Rodríguez-Martínez, Jesús, 2007, Stratigraphy, structure, and geologic and coastal hazards in the Peñuelas to Salinas area, southern Puerto Rico: A compendium of published literature: U.S. Geological Survey Open-File Report 2007-1259, 27 p. iii Contents Abstract .............................................................................................................................................1 Introduction .......................................................................................................................................2 Purpose and Scope ...................................................................................................................2 Geomorphology of the Study Area ...........................................................................................2 Geology .............................................................................................................................................3 Stratigraphy ..............................................................................................................................3 Early Tertiary Age and Older Rocks ..................................................................................3 Middle Tertiary Age Rocks ...............................................................................................4 Juana Díaz Formation ...............................................................................................4 Unnamed Pelagic Rocks or Deposits ........................................................................5 Ponce Limestone ......................................................................................................5 Quaternary Age Fan-Delta and Alluvial Deposits ............................................................5 Structure ...................................................................................................................................6 Great Southern Puerto Rico Fault Zone ............................................................................7 Late Quaternary Faulting ..................................................................................................7 Geologic Risks ...................................................................................................................................7 Spatial and Temporal Distribution of Seismic Activity .............................................................8 Potential for Liquefaction, Landslides and Tsunamis ...............................................................9 Summary .........................................................................................................................................11 References Cited .............................................................................................................................12 Glossary...........................................................................................................................................14 iv Figures 1. Map showing location of the Peñuelas to Salinas study area .......................................15 2. Map showing surficial geology of the Peñuelas to Salinas study area .........................16 3. Recent stratigraphic nomenclatures used in the study area ..........................................17 4. Geologic section across southern Puerto Rico fan-delta plain .......................................18 5–15. Maps showing 5. Major facies of the Ponce Limestone and equivalent beds .....................................19 6. Thickness of the fan-delta and alluvial deposits ......................................................20 7. Percentage of sand and gravel in the fan-delta plain deposits ...............................21 8. Location and orientation of the Great Southern Puerto Rico Fault zone in the study area ....................................................................................................22 9. Major tectonic faults and historic earthquakes in Puerto Rico and its vicinity ....................................................................................................................23 10. Geographical distribution of the magnitude of completeness values in Puerto Rico and its vicinity as determined from the Puerto Rico Seismic Network Catalog for the interval January 1986-March 2006 .................23 11. Seismicity density in Puerto Rico and its vicinity .....................................................23 12. Inland extent of tsunami-induced flooding in the Punta Verraco and Punta Cuchara quadrangles ...................................................................................24 13. Inland extent of tsunami-induced flooding in the Playa de Ponce quadrangle .............................................................................................................25 14. Inland extent of tsunami-induced flooding in the Santa Isabel quadrangle ............26 15. Inland extent of tsunami-induced flooding in the Salinas quadrangle ....................27 Tables 1. Estimated peak ground acceleration (PGA) in the study area from selected sources. ..........................................................................................................................9 2. Maximum inland extent of tsunami-induced coastal flooding within the study area. ......................................................................................................................1 v Conversion Factors, Datum, and Acronyms Multiply By To obtain Length inch (in.) 2.54 centimeter (cm) inch (in.) 25.4 millimeter (mm) foot (ft) 0.3048 meter (m) mile (mi) 1.609 kilometer (km) feet per mile (ft/mi) 0.1905 meter per kilometer (m/km) feet per squared second (ft/s2) 0.3048 meter per squared second (m/s2) Area square foot (ft2) 929.0 square centimeter (cm2) square foot (ft2) 0.09290 square meter (m2) square mile (mi2) 2.590 square kilometer (km2) Datum: Horizontal Datum - Puerto Rico Datum, 1940 Adjustment Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929) -- a geodetic datum derived from general adjustments of the first-order level nets of both the United States and Canada, formerly called “Sea Level Datum of 1929.” Acronyms used in this report: GNPRFZ Great Northern Puerto Rico Fault Zone GSPRFZ Great Southern Puerto Rico Fault Zone PGA peak ground acceleration PRDNER Puerto Rico Department of Natural and Environmental Resources PREPA Puerto Rico Electric Power Authority PREQB Puerto Rico Environmental Quality Board PRSN Puerto Rico Seismic Network USGS U.S. Geological Survey UPRM University of Puerto Rico at Mayagüez Translations Spanish English Lago Lake Río River Stratigraphy, Structure, and Geologic and Coastal Hazards in the Peñuelas to Salinas Area, Southern Puerto Rico: A Compendium of Published Literature By Jesús Rodríguez-Martínez Abstract per square mile, which is close to the average for The Puerto Rico Electrical Power Authority has southwestern Puerto Rico. proposed construction of a pipeline to convey natural The estimated maximum peak ground acceleration gas from the municipio of Peñuelas to the Aguirre most likely to occur in the study area, due to shallow thermoelectric power plant in the municipio of Salinas depth seismicity with 2 percent probability of in southern Puerto Rico. To ensure that the geologic exceedance in 50 years, is 9 feet per second squared, as conditions along the possible routes do not represent a obtained by modeling results. The estimated peak ground threat to the physical integrity of the natural gas pipeline, acceleration with 2 percent probability of exceedance and thus comply with State and Federal regulations, in 50 years, due to deep seismicity is 7 feet per second the Puerto Rico Electrical Power Authority requested squared. In Ponce, the probability of exceedance per year the U.S. Geological Survey to provide a synthesis of is higher than 0.1 for the peak ground acceleration values published literature of the geology of the coastal plain in less than 1 that result from shallow depth seismicity the Peñuelas to