1. Significant damage can be caused by blasts that are well within the regulatory limits. Blasts within regulatory limits are not difficult to achieve, and seismograph data can back up mine operator claims that blasts were within limits. Many problems are not caused by mine operators violating the limits, but by the fact that the limits are largely meaningless.
2. Seismographs should be placed outside and adjacent to a structure. Seismographs will sometimes be placed in the basement of houses. Seismographs placed in basements will read ground level or below-surface vibrations, not structure response.
3. Mine operators often stall installation of seismographs until after they have changed their blast designs to ensure they are within the limits. Study mine blasting records and compare blasts during monitoring with blasts prior to monitoring - this should reveal if designs have changed to ensure compliance.
4. Results of seismographs can be skewed through different analysis methods, different compliance methods, picking and choosing which parameters to report, strategic placement of spoil piles, and other actions available to the mine operator.
5. Peak particle velocity levels can vary significantly from one spot to another. Mine operators will usually try to locate seismographs away from "hot spots." The DEP will then use this data and apply it to the whole property, despite the existence of areas with higher values.