Tri-axial digital sensors for an earthquake resilient city

The city of Karachi is the largest city in Pakistan and the capital of the province of Sindh. Being the financial and commercial hub of Pakistan, the city of Karachi has been declared amongst the seismic hit zones of the country. The historical earthquakes detected in this region were appeared to be at locations 23.7 N 67.5 and 25.0 N 66.7. Although the seismic activity in this city is least, nevertheless, its prolong negligence is a matter of concern keeping in view the commercial importance associated to the area. In erecting the buildings of strategic importance in Karachi, no care has been made so far as to comply with international building codes.
Hence most of the buildings in the city are not likely to sustain seismic shaking, if it strikes. A research regarding the development of seismic resilient network for revamping existing buildings’ infrastructure of Karachi was conducted. For achieving the desired objectives, some sites were selected to detect potential of the seismic threat. The Karachi Seismic Monitoring Network (KSMON) infrastructure includes 35 onsite stations and one data processing station which are electronically connected with country’s other alerting systems to provide beforehand warning information to the population and first responders in case of any severe impending natural disaster. The network is being deployed along the potential sites of seismic threats which detect the individual events, calculates location and size and traces of shaking are transmitted to the remote monitoring station using communication channels both wired and wireless. These sites of seismic threats are high rise buildings, critical installations and places of densely populated regions. The KSMON is composed of MEMS accelerometers, velocity and displacement sensors connected through DSL, Wireless and point to point radio wave communication systems with following two main sections:
1. KSMON Onsite Stations (KOS)
2. KSMON Data Processing Stations (KDPS)
The KSMON onsite stations (KOS) are equipped with Guralp Systems’ instrumentation. Managed with solar panels possessing seven days fully operational autonomy, each of the KOS fixed on the earth or wall is calibrated with GSM/GPRS alarm systems connected with remote data processing and monitoring stations and also to the environmental and industrial sensors for emergency shut off through intelligent data logger.
Through strategically installed strong motion digital sensors at various locations and floors of the buildings in the city, the real time traces are obtained. The anomalies between the traces are analysed at various time stamps and these are correlated with the pre-defined samples of the vibration modes of each of the sites. These differences are then used to invoke decisions in respect of strengthening the respective structures before any seismic event is occurred in future. The real time vibration information is also disseminated to data processing and recording centres and to the concerned users. The analysis of communication channels for best fit scenarios over the performance matrix of link quality, link reliability, guaranteed data transfer, error control, QoS, jitter, packet loss and throughput in relaying the data to the users and to the data processing station are performed using OPNET software and based upon the simulated results, the network was installed. The system is capable of producing results for week building structures after detecting strong motion signals through installed digital seismic sensors.