A geochemical reconnaissance of the Utuado Batholith and vicinity, Puerto Rico

Learned, R.E.; Hickey, T.H.; Gonzales, Ileana. Perez de

doi:10.3133/ofr811131

Cited by 2 publications

(1 citation statement)

References 2 publications

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“…The root network in the uppermost soil profile section is denser (≤30% of the soil mass) and coarser (≤1 cm) than at Utuado. Utuado soil is a silty sand (Table 1) derived from the granodiorite-quartz diorite of the Utuado batholith (Learned, Hickey, & Perez de Gonzales, 1981) with a saturated hydraulic conductivity (K s ) that ranges from 3.6 to 147.6 mm/hr (geometric mean = 7.8 mm/hr; Table 2). Toro Negro exhibits more textural variability than Utuado (Table 1), but can generally be classified as a volcaniclastic-derived (Bawiec, 1998) plastic clayey silt with a K s that is considerably lower than Utuado, ranging from 0.3 to 2.5 mm/hr (geometric mean = 0.7 mm/hr; Table 2).…”

Section: Study Region and Hillslope Hydrologic Monitoring Sitesmentioning

confidence: 99%

Hillslopes in humid‐tropical climates aren't always wet: Implications for hydrologic response and landslide initiation in Puerto Rico

Thomas

Mirus

Smith

2020

Hydrological Processes

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The devastating impacts of the widespread flooding and landsliding in Puerto Rico following the September 2017 landfall of Hurricane Maria highlight the increasingly extreme atmospheric disturbances and enhanced hazard potential in mountainous humid-tropical climate zones. Long-standing conceptual models for hydrologically driven hazards in Puerto Rico posit that hillslope soils remain wet throughout the year, and therefore, that antecedent soil wetness imposes a negligible effect on hazard potential. Our post-Maria in situ hillslope hydrologic observations, however, indicate that while some slopes remain wet throughout the year, others exhibit appreciable seasonal and intra-storm subsurface drainage. Therefore, we evaluated the performance of hydro-meteorological (soil wetness and rainfall) versus intensityduration (rainfall only) hillslope hydrologic response thresholds that identify the onset of positive pore-water pressure, a predisposing factor for widespread slope instability in this region. Our analyses also consider the role of soil-water storage and infiltration rates on runoff generation, which are relevant factors for flooding hazards. We found that the hydro-meteorological thresholds outperformed intensity-duration thresholds for a seasonally wet, coarse-grained soil, although they did not outperform intensityduration thresholds for a perennially wet, fine-grained soil. These end-member soils types may also produce radically different stormflow responses, with subsurface flow being more common for the coarse-grained soils underlain by intrusive rocks versus infiltration excess and/or saturation excess for the fine-grained soils underlain by volcaniclastic rocks. We conclude that variability in soil-hydraulic properties, as opposed to climate zone, is the dominant factor that controls runoff generation mechanisms and modulates the relative importance of antecedent soil wetness for our hillslope hydrologic response thresholds.

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Section: Study Region and Hillslope Hydrologic Monitoring Sitesmentioning

confidence: 99%

Hillslopes in humid‐tropical climates aren't always wet: Implications for hydrologic response and landslide initiation in Puerto Rico

Thomas

Mirus

Smith

2020

Hydrological Processes

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Crustal Architecture of Puerto Rico Using Body-Wave Seismic Tomography and High-Resolution Earthquake Relocation

Lin

Huerfano

Fan

2021

Seismological Research Letters

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Puerto Rico is a highly seismically active island, where several damaging historical earthquakes have occurred and frequent small events persist. It situates at the boundary between the Caribbean and North American plates, featuring a complex fault system. Here, we investigate the seismotectonic crustal structure of the island by interpreting the 3D compressional-wave velocity VP and compressional- to shear-wave velocity ratio VP/VS models and by analyzing the distribution of the relocated earthquakes. The 3D velocity models are obtained by applying the simul2000 tomographic inversion algorithm based on the phase arrivals recorded by the Puerto Rico seismic network. We find high-VP and low-VP/VS anomalies in the eastern and central province between the Great Northern Puerto Rico fault zone and the Great Southern Puerto Rico fault zone, correlating with the Utuado pluton. Further, there are low-VP anomalies beneath both the Great Southern Puerto Rico fault zone and the South Lajas fault, indicating northerly dipping structures from the southwest to the northwest of the island. We relocate 19,095 earthquakes from May 2017 to April 2021 using the new 3D velocity model and waveform cross-correlation data. The relocated seismicity shows trends along the Investigator fault, the Ponce faults, the Guayanilla rift, and the Punta Montalva fault. The majority of the 2019–2021 Southwestern Puerto Rico earthquakes are associated with the Punta Montalva fault. Earthquakes forming 17° northward-dipping structures at various depths possibly manifest continuation of the Muertos trough, along which the Caribbean plate is being subducted beneath the Puerto Rico microplate. Our results show complex fault geometries of a diffuse fault network, suggesting possible subduction process accommodated by faults within a low-velocity zone.

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A geochemical reconnaissance of the Utuado Batholith and vicinity, Puerto Rico

Cited by 2 publications

References 2 publications

Hillslopes in humid‐tropical climates aren't always wet: Implications for hydrologic response and landslide initiation in Puerto Rico

Hillslopes in humid‐tropical climates aren't always wet: Implications for hydrologic response and landslide initiation in Puerto Rico

Crustal Architecture of Puerto Rico Using Body-Wave Seismic Tomography and High-Resolution Earthquake Relocation

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