Tsunami early warning using GPS‐Shield arrays

Abstract

The 2004 catastrophic Indian Ocean tsunami has strongly emphasized the need for reliable tsunami early warning systems. Another giant tsunamigenic earthquake may occur west of Sumatra, close to the large city of Padang. We demonstrate that the presence of islands between the trench and the Sumatran coast makes earthquake‐induced tsunamis especially sensitive to slip distribution on the rupture plane as wave heights at Padang may differ by more than a factor of 5 for earthquakes having the same seismic moment (magnitude) and rupture zone geometry but different slip distribution. Hence reliable prediction of tsunami wave heights for Padang cannot be provided using traditional, earthquake‐magnitude‐based methods. We show, however, that such a prediction can be issued within 10 minutes of an earthquake by incorporating special types of near‐field GPS arrays (“GPS‐Shield”). These arrays measure both vertical and horizontal displacements and can resolve higher order features of the slip distribution on the fault than the seismic moment if placed above the rupture zone or are less than 100 km away of the rupture zone. Stations in the arrays are located as close as possible to the trench and are aligned perpendicular to the trench, i.e., parallel to the expected gradient of surface coseismic displacement. In the case of Sumatra and Java, the GPS‐Shield arrays should be placed at Mentawai Islands, located between the trench and Sumatra and directly at the Sumatra and Java western coasts. We demonstrate that the “GPS‐Shield” can also be applied to northern Chile, where giant earthquakes may also occur in the near future. Moreover, this concept may be applied globally to many other tsunamigenic active margins where the land is located above or close to seismogenic zones.

A new multi-sensor approach to simulation assisted tsunami early warning

“…In particular, realtime GPS measurements of the earth crust displacement and wave gauge information (and here most prominently arrival time information) can beneficially be used in this context (Sobolev et al, 2007).…”

“…The reliability for this case is 0.44. Data from real-time GPSarrays are available in just a few minutes after the earthquake event, which makes this type of data very valuable for the near-field early warning (Sobolev et al, 2007).…”

Improved GPS‐based coseismic displacement monitoring using high‐precision oscillators

“…Geophysical investigations benefit from these developments enabling the analysis of various high-frequency phenomena. Prominent examples are volcano monitoring [Larson et al, 2010], subdaily strain estimation [Reuveni et al, 2012], tsunami prediction [Sobolev et al, 2007;Blewitt et al, 2009;Falck et al, 2010], and studies of coseismic displacements [Avallone et al, 2011;Larson, 2009;Wang et al, 2012]. Especially for large earthquakes the GNSS approach has advantages compared to seismometers because it does not saturate and directly provides displacements thus avoiding the uncertainties associated with integrating the acceleration records of strong motion instruments.…”

Near real-time GPS applications for tsunami early warning systems

“…Onshore GPS measurements are made collocated with tide gauges or seismological stations and give information about co-seismic land mass movements as recorded, e.g., during the great Sumatra-Andaman earthquake of 2004 (Subarya et al, 2006). This information is important to separate tsunami-caused sea height movements from apparent sea height changes at tide gauge locations (sensor station movement) and also as additional information about earthquakes' mechanisms, as this is an essential information to predict a tsunami (Sobolev et al, 2007).This article gives an end-to-end overview of the GITEWS GPS-component system, from the GPS sensors (GPS receiver with GPS antenna and auxiliary systems, either onshore or offshore) to the early warning centre displays. We describe how the GPS sensors have been installed, how they are operated and the methods used to collect, transfer and…”

“…Onshore GPS measurements are made collocated with tide gauges or seismological stations and give information about co-seismic land mass movements as recorded, e.g., during the great Sumatra-Andaman earthquake of 2004 (Subarya et al, 2006). This information is important to separate tsunami-caused sea height movements from apparent sea height changes at tide gauge locations (sensor station movement) and also as additional information about earthquakes' mechanisms, as this is an essential information to predict a tsunami (Sobolev et al, 2007).…”