California Seismic Hazards Mapping Act (SHMA) of 1990 — Compliance Brief
Record covered: geotechnical-cert-019 Issuing body: California Legislature (statute: Public Resources Code §§2690–2699.6); administered by the California Geological Survey (CGS); implemented by cities and counties through their permitting authority. Jurisdiction: California only. Status: Current law, enacted 1990 after the 1989 Loma Prieta earthquake. CGS updates the official maps over time; the regulatory mechanism is unchanged.
1. What it is
The SHMA is California's law for keeping new development off unmitigated seismic ground-failure hazards. It requires CGS to map Zones of Required Investigation for three hazards — liquefaction, earthquake-induced landslides, and amplified ground shaking — and requires cities and counties to withhold building permits within those zones until a site-specific geotechnical investigation demonstrates the hazard is mitigated. It is the reason a large share of California geotechnical practice exists: the Act manufactures the demand for seismic-hazard investigations by statute.
Its sibling is the Alquist-Priolo Earthquake Fault Zoning Act (1972), which maps fault-rupture zones — SHMA covers the ground-failure hazards, Alquist-Priolo the fault-rupture hazard. Together they are California's seismic land-use regime.
2. Scope — who and what it applies to
- CGS must produce and update official Seismic Hazard Zone maps delineating Zones of Required Investigation.
- Cities and counties must require geotechnical investigations before issuing permits for most developments within mapped zones, and must transmit investigation reports to CGS.
- Developers and owners of projects in mapped zones must fund and perform the site-specific investigation.
- Licensed professionals: investigations must be performed under responsible charge of appropriately licensed professionals — in practice California-licensed Geotechnical Engineers (GE) and Certified Engineering Geologists (CEG), often working with PGs. The Act is what makes the GE title authority commercially valuable.
3. Key requirements and compliance obligations
- Check the maps first: every California project starts with a CGS Seismic Hazard Zone map query — is the site in a liquefaction zone, an earthquake-induced landslide zone, or both?
- Site-specific investigation where zoned: subsurface exploration, laboratory testing, and quantitative hazard analysis (liquefaction triggering and settlement analysis; slope stability under seismic loading; site-response/ground-motion analysis for amplified shaking).
- Mitigation demonstration: the investigation must show the hazard is mitigated to an acceptable level — through ground improvement (densification, stone columns, deep soil mixing), deep foundations bearing below liquefiable layers, structural design for the computed settlements/lateral spread, or slope stabilization — or the permit is withheld.
- Report and review: reports go to the local permitting agency (which often requires independent peer review for complex projects) and are transmitted to CGS, building the state's public archive of hazard investigations.
- Waivers: the Act provides for waivers where the local agency finds, based on technical evidence, that no hazard exists — narrowly applied in practice.
4. Penalties / consequences
The Act's enforcement is permit-based, not fine-based: non-compliance means no permit — the project stops. Building without the required investigation exposes the owner to stop-work orders, permit revocation, and orders to remediate. For design professionals, the exposure is liability: a geotechnical report that misses a mapped hazard, or a mitigation design that fails in an earthquake, faces negligence claims amplified by the fact that the statute required the investigation — the duty of care is legislatively established. Insurers and lenders treat SHMA-zone compliance as a condition of financing California projects.
5. Version and edition status — live changes
The statute is stable since 1990; the moving part is the maps — CGS releases new and revised Seismic Hazard Zone maps on an ongoing quadrangle-by-quadrangle program. Always query the current official CGS maps, not a cached copy: zones expand as mapping advances, and a site clear five years ago may be zoned today. CGS also publishes Special Publication 117A (guidelines for evaluating and mitigating seismic hazards), the technical standard of practice for SHMA investigations — its current edition governs methodology expectations.
6. Related certifications
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Geotechnical — California Geotechnical Engineer (GE) Title Authority (geotechnical-cert-002): the specialty license that stamps SHMA investigations — this Act is the primary economic engine for the GE credential.
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Geotechnical — Certified Engineering Geologist, CEG (geotechnical-cert-004) and Professional Geologist, PG (geotechnical-cert-003): the geologic-investigation side of SHMA compliance (landslide and liquefaction susceptibility mapping).
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Geotechnical — PE Civil: Geotechnical (geotechnical-cert-001): the underlying civil license; the GE is a title authority added to it.
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Lender and insurer reliance: because SHMA investigations are public records transmitted to CGS, subsequent buyers, lenders, and insurers can (and do) pull prior reports - a thin or evasive investigation follows the property and the professional's reputation. Scope the work to withstand third-party review, not just to clear the permit counter.
7. Flags and honest caveats
- This brief covers the SHMA mechanism; the Alquist-Priolo fault-rupture program is adjacent law with its own zones and setback rules — a complete California seismic due-diligence check covers both.
- Map currency is everything: the compliance answer for a specific parcel is only as good as the latest CGS map release for that quadrangle.
Original ETS reference writing, verified against public sources on 2026-09-30. Thin sourcing is flagged inline. Not legal advice — confirm current editions with the issuing body.