Abstract Long-term continuous monitoring in the Houston-Galveston area indicates that, during the past two decades (1993-2012), the overall land subsidence has been decreasing, while the groundwater head has been increasing. Subsidence in downtown Houston, the area along the Houston Ship Channel, and the coastal area of Galveston has almost ceased. Slight ground surface rebound has been observed at several sites along the Houston Ship Channel. Assuming that the hydraulic head in the aquifer will reach or exceed the preconsolidation level in the near future, will the subsidence in the Houston-Galveston area eventually cease? The key to answering this question is to identify if there is deep-seated subsidence in this area. This study investigated the recent subsidence observed at different depths in the Houston-Galveston area. The subsidence was recorded by using 13 borehole extensometers and 76 GPS antennas. Four of the antennas are mounted on the deep-anchored (549, 591, 661 and 936 m below the land surface) inner pipes of borehole extensometers. We conclude that recent subsidence (1993-2012) in the Houston-Galveston area was dominated by the compaction of sediments within 600 m below the land surface. Depending on the location of specific sites, the compaction occurred within the Chicot and part or all of the Evangeline aquifer. No measurable compaction was observed within the Jasper aquifer or within deeper strata. Recent GPS observations also suggest that there is currently no considerable lateral ground deformation or subsidence associated with deep-rooted faulting activities in the Houston-Galveston area.

Abstract Each year from June through November, tropical cyclones are a common potential problem for those living in coastal communities along the southwest Louisiana and southeast Texas coasts. Developing from small tropical disturbances, tropical cyclone strength is determined by many factors: ocean temperature, upper and lower wind circulation, latitudinal position, etc. Ecological, geological, and economic effects of strong-to-devastating tropical cyclones on coastal areas are typically extreme. Since the 1860s, seven strong or greater tropical cyclones have struck the Louisiana-Texas coast. Their impact has made an indelible impression on the coastline as well as on the communities in the area

Abstract Ground failures, ranging from long tension cracks or fissures to surface faults, are caused by man-induced water-level declines in more than 14 areas in the contiguous United States. These failures are associated with land subsidence caused by compaction of underlying unconsolidated sediment. Fissures, which range in length from dekameters to kilometers, typically open only a few centimeters by displacement but are eroded by surface runoff into gullies 1 to 2 m wide and 2 to 3 m deep. Surface faults commonly attain scarp heights of 0.5 m and lengths of 1 km; the highest and longest scarps are 1 m and 16.7 km, respectively. Scarps grow by aseismic creep at rates approximately ranging from 4 to 60 mm/yr; modern fault movement is high angle and normal. Fault movement commonly correlates with seasonal water-level fluctuations, and examples of seasonal water-level recoveries halting fault movement have been reported. The greatest economic impact from ground failure is in the Houston-Galveston, Texas, metropolitan region where more than 86 surface faults have caused millions of dollars of damage and losses of property value. Most ground failures probably are caused by localized differential compaction, although this mechanism has not been demonstrated everywhere. Earth fissures formed by this mechanism are caused by stretching related to bending of the overburden that overlies the differentially compacting zone. Surface faults form when differential compaction is discrete across preexisting faults. Fissures that form complex polygonal patterns probably are caused by tension induced by capillary stresses in the zone above a declining water table. Ground failures can be predicted either by determining potential areas of differential compaction or by monitoring surface deformation in areas of ongoing water-level decline. Potential ground-failure sites can be resolved by either technique to within a few dekameters.

Abstract Though Memoir 21 was first published in 1974, the concepts and illustrations are timeless for those interested in stratigraphic exploration for sandstone reservoirs. Quickly the reader will note the same relationships in sequence stratigraphy recognized by the author. For university earth science majors and less experienced members of the energy industry, the CD is presented as a reference work. The concepts of depositional control on the distribution of sandstone reservoirs is critical to understand no matter the terminology used. With the kind permission of Dr. Daniel A. Busch, this memoir now can become part of your exploration library.