Tech Sessions Speaker Series: Dr. Andrew Smye

Tech Sessions Speaker Series: Dr. Andrew Smye

UTIG Seminar Series: Aaron Wech, U.S. Geological Survey

"Using Messy Seismicity to Investigate Earthquakes and Plate Boundary Dynamic"

Abstract:

Tectonic tremor, a messy seismic signal characterized by enduring 1-10 Hz signals, is observed beneath the locked zone of many faults. In subduction zones, it is often accompanied by slow slip, an intermediate mechanism for accommodating plate motion between a megathrust rupture and stable sliding. While it is evident these phenomena play a critical role in relieving stress on the plate interface, the nature of these signals makes tracking them difficult, however, and a clear understanding of the processes controlling their behavior remains elusive. Here I’ll try and make the case that tracking this behavior is both interesting and important by presenting an overview of we do and don’t know, how it relates to hazards, and what it means for the physics of earthquakes and plate boundary dynamics.

Tech Sessions Speaker Series: Dr. Andrew Smye

UTIG Seminar Series: Aaron Wech, U.S. Geological Survey

"Using Messy Seismicity to Investigate Earthquakes and Plate Boundary Dynamic"

Abstract:

Tectonic tremor, a messy seismic signal characterized by enduring 1-10 Hz signals, is observed beneath the locked zone of many faults. In subduction zones, it is often accompanied by slow slip, an intermediate mechanism for accommodating plate motion between a megathrust rupture and stable sliding. While it is evident these phenomena play a critical role in relieving stress on the plate interface, the nature of these signals makes tracking them difficult, however, and a clear understanding of the processes controlling their behavior remains elusive. Here I’ll try and make the case that tracking this behavior is both interesting and important by presenting an overview of we do and don’t know, how it relates to hazards, and what it means for the physics of earthquakes and plate boundary dynamics.

BEG Friday Seminar Series

Brian A. Smith, PhD, PG
Aquifer Science Team Leader
Barton Springs/Edwards Aquifer Conservation District

Hydrologic Influences of the Blanco River on the
Trinity and Edwards Aquifers, Central Texas

Abstract:
The Blanco River of central Texas provides an important hydrologic link between surface and groundwater as it traverses two major karst aquifer systems—the Trinity and Edwards Aquifers. The Blanco River is characterized by alternating gaining and losing stretches due to the presence of springs that discharge water into the river and swallets that drain water from the river. Trinity units outcrop in the western part of the study area, and Edwards units outcrop in the eastern part of the study area. Normal faulting along the Balcones Fault Zone has juxtaposed the older, underlying Trinity units against the Edwards units. The region consists primarily of Cretaceous limestone, dolomite, and marls. One of the more significant springs along the Blanco River is Pleasant Valley Spring. During below-average flow conditions, Pleasant Valley Spring becomes the headwaters of the Blanco River even though the headwaters, under wet conditions, are about 50 km upstream. Water that enters the Edwards Aquifer from the Blanco River can eventually discharge at both San Marcos Springs to the south and Barton Springs to the north. Tracer tests have confirmed flow to both springs under drought conditions. During periods of extreme drought, when other recharging streams are dry, the Blanco River can provide enough water to the Edwards Aquifer that will help maintain flow at Barton Springs. Some of the water recharging the Trinity Aquifer enters a deep flow system that has been penetrated by monitor and water-supply well at depths of about 400 m on the east side of the study area. In this area, low-permeability units of the Upper Trinity provide hydraulic separation between the water-bearing Middle Trinity and the overlying Edwards. Potentiometric and geochemical data suggest that water encountered in these deep Middle Trinity units comes from recharge areas along the Blanco River where the units are exposed at the surface. In the western part of the study area increasing rates of pumping from the Trinity Aquifer are reducing heads in the aquifer and are subsequently reducing springflows (such as from Jacob's Well and Pleasant Valley Spring) that sustain the Blanco River. Decreasing flow in the Blanco River can lead to less recharge to the Edwards Aquifer and less discharge from San Marcos and Barton Springs. A better understanding of these aquifer systems and how they are influenced by the Blanco River is important for management of groundwater in an area undergoing significant population growth.

Tech Sessions Speaker Series: Dr. Andrew Smye

UTIG Seminar Series: Aaron Wech, U.S. Geological Survey

"Using Messy Seismicity to Investigate Earthquakes and Plate Boundary Dynamic"

Abstract:

Tectonic tremor, a messy seismic signal characterized by enduring 1-10 Hz signals, is observed beneath the locked zone of many faults. In subduction zones, it is often accompanied by slow slip, an intermediate mechanism for accommodating plate motion between a megathrust rupture and stable sliding. While it is evident these phenomena play a critical role in relieving stress on the plate interface, the nature of these signals makes tracking them difficult, however, and a clear understanding of the processes controlling their behavior remains elusive. Here I’ll try and make the case that tracking this behavior is both interesting and important by presenting an overview of we do and don’t know, how it relates to hazards, and what it means for the physics of earthquakes and plate boundary dynamics.

BEG Friday Seminar Series

Brian A. Smith, PhD, PG
Aquifer Science Team Leader
Barton Springs/Edwards Aquifer Conservation District

Hydrologic Influences of the Blanco River on the
Trinity and Edwards Aquifers, Central Texas

Abstract:
The Blanco River of central Texas provides an important hydrologic link between surface and groundwater as it traverses two major karst aquifer systems—the Trinity and Edwards Aquifers. The Blanco River is characterized by alternating gaining and losing stretches due to the presence of springs that discharge water into the river and swallets that drain water from the river. Trinity units outcrop in the western part of the study area, and Edwards units outcrop in the eastern part of the study area. Normal faulting along the Balcones Fault Zone has juxtaposed the older, underlying Trinity units against the Edwards units. The region consists primarily of Cretaceous limestone, dolomite, and marls. One of the more significant springs along the Blanco River is Pleasant Valley Spring. During below-average flow conditions, Pleasant Valley Spring becomes the headwaters of the Blanco River even though the headwaters, under wet conditions, are about 50 km upstream. Water that enters the Edwards Aquifer from the Blanco River can eventually discharge at both San Marcos Springs to the south and Barton Springs to the north. Tracer tests have confirmed flow to both springs under drought conditions. During periods of extreme drought, when other recharging streams are dry, the Blanco River can provide enough water to the Edwards Aquifer that will help maintain flow at Barton Springs. Some of the water recharging the Trinity Aquifer enters a deep flow system that has been penetrated by monitor and water-supply well at depths of about 400 m on the east side of the study area. In this area, low-permeability units of the Upper Trinity provide hydraulic separation between the water-bearing Middle Trinity and the overlying Edwards. Potentiometric and geochemical data suggest that water encountered in these deep Middle Trinity units comes from recharge areas along the Blanco River where the units are exposed at the surface. In the western part of the study area increasing rates of pumping from the Trinity Aquifer are reducing heads in the aquifer and are subsequently reducing springflows (such as from Jacob's Well and Pleasant Valley Spring) that sustain the Blanco River. Decreasing flow in the Blanco River can lead to less recharge to the Edwards Aquifer and less discharge from San Marcos and Barton Springs. A better understanding of these aquifer systems and how they are influenced by the Blanco River is important for management of groundwater in an area undergoing significant population growth.

Soft Rock Seminar: Kelsi Ustipak