Strong Motion Networks
Strong Motion Seismology may be referred to as science and technology based on strong motion network data and earthquake disaster records near earthquake sources. The objective of creating strong motion networks is to generate data to study source dynamics of generated ground motions from seismic sources. Furthermore, the analysis of seismic-wave propagation effects due to complex geological structures in propagation-path from source to site, including wave attenuation and scattering. Finally, the amplification and de-amplification of seismic motions due to surface geological and topography, including nonlinear behaviour of soils for strong motions. Then as a goal, it is to develop methodologies (a.k.a. GMPEs) of predicting strong ground motions from seismic sources related to active faults and subduction-zones with high probability of earthquake occurrence in order to mitigate earthquake disaster.
The data generated from Strong Motion Networks are used for earthquake emergency response, for improving engineering designs, and for research in seismology. For earthquake emergency response, applications such as the ShakeMaps use strong-motion data as input and generate near-real time information on the levels of ground shaking and loss assessment for emergency responders. Structural and earthquake engineers use strong motion recordings to verify or improve design codes.
Case Study:Netquakes, USA
Any country as large as the USA faces difficult choices within its earthquake monitoring strategy. Striking the right balance between the possibility of a large earthquake in a remote area causing little disruption and a smaller earthquake in a densely populated causing massive damage has to be a risk very carefully managed.
A current area of significant risk has been identified as surrounding the San Francisco East Bay and the Hayward fault areas. The USGS is trying to achieve a denser and more uniform seismograph spacing in the Bay Area to provide better measurements of ground motion during earthquakes. To do this, the NetQuakes instruments are deployed that communicate their data to the USGS via the Internet. These instruments connect to an existing local network using WiFi and use existing Broadband connections to transmit data after an earthquake.
On 6 Jun 2009 a 3.1 earthquake rattled the East Bay but there were no immediate reports of injury or damage. Scientists then probed the Lucas Valley for earthquake clues as the one almost certain thing around the East Bay area is that something bigger now appears to be looming. On 25 Jun 2009 the USGS described the Hayward fault as ‘a tectonic time bomb, due anytime for another magnitude 6.8 to 7.0 earthquake and that the coming Hayward fault earthquake will probably kill hundreds of people and cause damage worth perhaps $100 billion‘. This locality has therefore been identified as an area where the precise seismic risk of earthquake is not yet fully understood.
New instrumentation has been sought to monitor this emerging situation and included finding suitable locations within built up areas to accept and install earthquake monitoring systems. The NetQuakes seismographs specification requires access the Internet via a wireless router connected to an existing Broadband Internet connection. The seismograph then transmits data to the USGS only after earthquakes above the magnitude of around 3, but will not consume any significant bandwidth and should require only minimal maintenance.
While enhancing the Strong Motion Network coverage in this seismically high-risk area, the measurements improve also the ability to make rapid post-earthquake assessments of expected damage and contribute to the continuing development of engineering standards for construction projects. They may well also shape future requirements within other urban areas over a longer time period.
> 300 Recorders
Strong Motion Recorder / Measuring System
Case Study:Strong Motion Instrumentation Project, India
National Strong Motion
Instrumentation Project India
The Department of Earthquake Engineering is the only one of its kind in India and amongst a few in the world being established in 1960 as the School of Research and Training in Earthquake Engineering. The department has undertaken programs of seismic instrumentation with a view to having a better understanding of the ground motion characteristics and seismicity of various regions.In India installation of power plants, river valley projects and other major constructions have been undertaken as part of modernisation and infrastructure development. Since more than 50% area of India is susceptible to strong earthquakes, it is essential to estimate and predict the characteristics of strong ground motion in future earthquakes that could arise in any region. A correct assessment of the proneness to destructive earthquakes in the different regions of India can only be achieved by having a database of records of strong ground motion from past earthquakes. This should then lead to a substantial saving in the design of structures as well as ensuring that the region has improved long-term stability against earthquakes.
For a huge country like India, installing a dense network (say at every 25 Km in active seismic zones) of digital accelerographs can be an expensive venture. In view of this, a low cost strong motion instrument called Structural Response Recorder (SRR) was designed and developed at the Department of Earthquake Engineering, IIT Roorkee (IITR).
The instruments provided were deployed within the “National Strong Motion Instrumentation Project” at Roorkee sponsored by Department of Science and Technology, Government of India under its Mission Mode Program on Seismology.
300 x Sensors
300 x Strong Motion Recorders
300 x TCP/IP Modules
140 x External Modems