Advanced Noninvasive Geophysical Monitoring Techniques

Abstract

Geophysical methods can be used to create images of the Earth's interior that constitute snapshots at the moment of data acquisition. In many applications, it is important to measure the temporal change in the subsurface, because the change is associated with deformation, fluid flow, temperature changes, or changes in material properties. We present an overview how noninvasive geophysical methods can be used for this purpose. We focus on monitoring mechanical properties, fluid transport, and biogeochemical processes, and present case studies that illustrate the use of geophysical method for detecting timelapse changes in associated properties. The examples include: measuring uplift of the Earth's surface, compaction near a producing hydrocarbon reservoir, the seismic detection of stress changes, monitoring buildings, the detection of fluid flow along a fault zone, electrical monitoring of fluid infiltration and redox potential, and electrical and seismic monitoring of microbially mediated processes. An overlying research question in geophysical monitoring concerns the use of these time-lapse changes, notably the assesment of uncertainty, the combination of disparate data, and the interface with those who make decisions based on time-lapse information.

Impulse Response of Civil Structures from Ambient Noise Analysis

“…Primarily, the shorter wait for enough time series data required by the method will allow more buildings to be analyzed with campaign-style, rapidly deployable, temporary arrays rather than (semi) permanent arrays (Ivanovic and Trifunac, 1995). The main difference between the method proposed here and other interferometry studies in buildings (Snieder and Safak, 2006;Kohler et al, 2007;Snieder et al, 2007) is that the data in previous studies use earthquake shaking, whereas we exclusively use ambient vibrations. Consequently, this method can also be used to perform propagating-wave-based system identification of buildings to complement modal-based methods, which is of key importance for damage assessment (Skolnik et al, 2006).…”

“…Usually, one would like to see if there are variations in modal parameters before and after major earthquakes (Snieder et al, 2007) or before and after retrofitting (Celebi and Liu, 1998).…”

“…This leads to the possibility of rapid structural monitoring through ambient vibrations without the need to wait for subsequent earthquakes as proposed in Snieder et al (2007). As discussed by Ivanovic et al (2000), monitoring using ambient vibrations has been used since the 1970s, mostly studying the modal shape variations.…”

On scale and magnitude of pressure build‐up induced by large‐scale geologic storage of CO2

“…The oilfields act like closed, partially closed, or open subsystems, evidenced by strong variations in pressure behavior observed during petroleum extraction. For example, the pressure decrease (induced by production of petroleum and produced water) observed at wells and the subsidence imaged using InSAR data indicate that the Kern River oilfield is a closed subsystem bounded by faults and a formation outcrop [23][24] . In summary, the Vedder Sand in the southern San Joaquin Basin forms a partially closed storage system with three closed boundaries and one open boundary, and comprises some localized, fault-bounded closed and partially closed subsystems.…”

Temporal changes of surface wave velocity associated with major Sumatra earthquakes from ambient noise correlation

“…Recent progress in passive imaging with random noise offers an alternative (e.g., reviewed in ref. 6).…”